diff --git a/lib/cmds/blockchain/geth_commands.js b/lib/cmds/blockchain/geth_commands.js
index f89c325a6..d6b1e4c5d 100644
--- a/lib/cmds/blockchain/geth_commands.js
+++ b/lib/cmds/blockchain/geth_commands.js
@@ -1,7 +1,7 @@
-var async = require('async');
+let async = require('async');
 
 // TODO: make all of this async
-var GethCommands = function(options) {
+let GethCommands = function(options) {
   this.config = options.config;
   this.env = options.env || 'development';
   this.name = "Go-Ethereum (https://github.com/ethereum/go-ethereum)";
@@ -9,8 +9,8 @@ var GethCommands = function(options) {
 };
 
 GethCommands.prototype.commonOptions = function() {
-  var config = this.config;
-  var cmd = "";
+  let config = this.config;
+  let cmd = "";
 
   cmd += this.determineNetworkType(config);
 
@@ -34,7 +34,7 @@ GethCommands.prototype.commonOptions = function() {
 };
 
 GethCommands.prototype.determineNetworkType = function(config) {
-  var cmd = "";
+  let cmd = "";
   if (config.networkType === 'testnet') {
     cmd += "--testnet ";
   } else if (config.networkType === 'olympic') {
@@ -46,8 +46,8 @@ GethCommands.prototype.determineNetworkType = function(config) {
 };
 
 GethCommands.prototype.initGenesisCommmand = function() {
-  var config = this.config;
-  var cmd = this.geth_bin + " " + this.commonOptions();
+  let config = this.config;
+  let cmd = this.geth_bin + " " + this.commonOptions();
 
   if (config.genesisBlock) {
     cmd += "init \"" + config.genesisBlock + "\" ";
@@ -65,7 +65,7 @@ GethCommands.prototype.listAccountsCommand = function() {
 };
 
 GethCommands.prototype.determineRpcOptions = function(config) {
-  var cmd = "";
+  let cmd = "";
 
   cmd += "--port " + config.port + " ";
   cmd += "--rpc ";
@@ -88,17 +88,17 @@ GethCommands.prototype.determineRpcOptions = function(config) {
 };
 
 GethCommands.prototype.mainCommand = function(address, done) {
-  var self = this;
-  var config = this.config;
-  var rpc_api = (this.config.rpcApi || ['eth', 'web3', 'net']);
+  let self = this;
+  let config = this.config;
+  let rpc_api = (this.config.rpcApi || ['eth', 'web3', 'net']);
 
   async.series([
     function commonOptions(callback) {
-      var cmd = self.commonOptions();
+      let cmd = self.commonOptions();
       callback(null, cmd);
     },
     function rpcOptions(callback) {
-      var cmd = self.determineRpcOptions(self.config);
+      let cmd = self.determineRpcOptions(self.config);
       callback(null, cmd);
     },
     function dontGetPeers(callback) {
@@ -114,7 +114,7 @@ GethCommands.prototype.mainCommand = function(address, done) {
       callback(null, "");
     },
     function maxPeers(callback) {
-      var cmd = "--maxpeers " + config.maxpeers;
+      let cmd = "--maxpeers " + config.maxpeers;
       callback(null, cmd);
     },
     function mining(callback) {
@@ -140,7 +140,7 @@ GethCommands.prototype.mainCommand = function(address, done) {
       callback(null, '--rpcapi "' + rpc_api.join(',') + '"');
     },
     function accountToUnlock(callback) {
-      var accountAddress = config.account.address || address;
+      let accountAddress = config.account.address || address;
       if (accountAddress) {
         return callback(null, "--unlock=" + accountAddress);
       }
diff --git a/lib/cmds/simulator.js b/lib/cmds/simulator.js
index 47554c123..6a9adde86 100644
--- a/lib/cmds/simulator.js
+++ b/lib/cmds/simulator.js
@@ -1,11 +1,11 @@
-var shelljs = require('shelljs');
+let shelljs = require('shelljs');
 
-var Simulator = function(options) {
+let Simulator = function(options) {
   this.blockchainConfig = options.blockchainConfig;
 };
 
 Simulator.prototype.run = function(options) {
-  var cmds = [];
+  let cmds = [];
 
   cmds.push("-p " + (this.blockchainConfig.rpcPort || options.port || 8545));
   cmds.push("-h " + (this.blockchainConfig.rpcHost || options.host || 'localhost'));
diff --git a/lib/cmds/template_generator.js b/lib/cmds/template_generator.js
index 42c632882..d2355a34d 100644
--- a/lib/cmds/template_generator.js
+++ b/lib/cmds/template_generator.js
@@ -1,12 +1,12 @@
-var fs = require('../core/fs.js');
-var utils = require('../utils/utils.js');
+let fs = require('../core/fs.js');
+let utils = require('../utils/utils.js');
 
-var TemplateGenerator = function(templateName) {
+let TemplateGenerator = function(templateName) {
   this.templateName = templateName;
 };
 
 TemplateGenerator.prototype.generate = function(destinationFolder, name) {
-  var templatePath = fs.embarkPath(this.templateName);
+  let templatePath = fs.embarkPath(this.templateName);
   console.log('Initializing Embark Template....'.green);
 
   fs.copySync(templatePath, destinationFolder + name);
diff --git a/lib/contracts/abi.js b/lib/contracts/abi.js
index 479b9f771..bede90dcd 100644
--- a/lib/contracts/abi.js
+++ b/lib/contracts/abi.js
@@ -1,5 +1,5 @@
 
-var ABIGenerator = function(options) {
+let ABIGenerator = function(options) {
   this.blockchainConfig = options.blockchainConfig || {};
   this.storageConfig = options.storageConfig || {};
   this.communicationConfig = options.communicationConfig || {};
@@ -10,9 +10,9 @@ var ABIGenerator = function(options) {
 };
 
 ABIGenerator.prototype.generateProvider = function() {
-  var self = this;
-  var result = "";
-  var providerPlugins;
+  let self = this;
+  let result = "";
+  let providerPlugins;
 
   if (self.blockchainConfig === {} || self.blockchainConfig.enabled === false) {
     return "";
@@ -39,9 +39,9 @@ ABIGenerator.prototype.generateProvider = function() {
 };
 
 ABIGenerator.prototype.generateContracts = function(useEmbarkJS) {
-  var self = this;
-  var result = "\n";
-  var contractsPlugins;
+  let self = this;
+  let result = "\n";
+  let contractsPlugins;
 
   if (self.blockchainConfig === {} || self.blockchainConfig.enabled === false) {
     return "";
@@ -56,11 +56,11 @@ ABIGenerator.prototype.generateContracts = function(useEmbarkJS) {
       result += plugin.generateContracts({contracts: self.contractsManager.contracts});
     });
   } else {
-    for(var className in this.contractsManager.contracts) {
-      var contract = this.contractsManager.contracts[className];
+    for(let className in this.contractsManager.contracts) {
+      let contract = this.contractsManager.contracts[className];
 
-      var abi = JSON.stringify(contract.abiDefinition);
-      var gasEstimates = JSON.stringify(contract.gasEstimates);
+      let abi = JSON.stringify(contract.abiDefinition);
+      let gasEstimates = JSON.stringify(contract.gasEstimates);
 
       if (useEmbarkJS) {
         result += "\n" + className + " = new EmbarkJS.Contract({abi: " + abi + ", address: '" + contract.deployedAddress + "', code: '" + contract.code + "', gasEstimates: " + gasEstimates + "});";
@@ -76,8 +76,8 @@ ABIGenerator.prototype.generateContracts = function(useEmbarkJS) {
 };
 
 ABIGenerator.prototype.generateStorageInitialization = function(useEmbarkJS) {
-  var self = this;
-  var result = "\n";
+  let self = this;
+  let result = "\n";
 
   if (!useEmbarkJS || self.storageConfig === {}) return "";
 
@@ -89,8 +89,8 @@ ABIGenerator.prototype.generateStorageInitialization = function(useEmbarkJS) {
 };
 
 ABIGenerator.prototype.generateCommunicationInitialization = function(useEmbarkJS) {
-  var self = this;
-  var result = "\n";
+  let self = this;
+  let result = "\n";
 
   if (!useEmbarkJS || self.communicationConfig === {}) return "";
 
@@ -104,7 +104,7 @@ ABIGenerator.prototype.generateCommunicationInitialization = function(useEmbarkJ
 };
 
 ABIGenerator.prototype.generateABI = function(options) {
-  var result = "";
+  let result = "";
 
   result += this.generateProvider();
   result += this.generateContracts(options.useEmbarkJS);
diff --git a/lib/contracts/contracts.js b/lib/contracts/contracts.js
index 4123f543b..e6e2dc875 100644
--- a/lib/contracts/contracts.js
+++ b/lib/contracts/contracts.js
@@ -1,12 +1,12 @@
-var toposort = require('toposort');
-var async = require('async');
+let toposort = require('toposort');
+let async = require('async');
 
-var Compiler = require('./compiler.js');
+let Compiler = require('./compiler.js');
 
 // TODO: create a contract object
 
-var adjustGas = function(contract) {
-  var maxGas, adjustedGas;
+let adjustGas = function(contract) {
+  let maxGas, adjustedGas;
   if (contract.gas === 'auto') {
     if (contract.deploy || contract.deploy === undefined) {
       if (contract.gasEstimates.creation !== undefined) {
@@ -25,7 +25,7 @@ var adjustGas = function(contract) {
   }
 };
 
-var ContractsManager = function(options) {
+let ContractsManager = function(options) {
   this.contractFiles = options.contractFiles;
   this.contractsConfig = options.contractsConfig;
   this.contracts = {};
@@ -36,17 +36,17 @@ var ContractsManager = function(options) {
 };
 
 ContractsManager.prototype.build = function(done) {
-  var self = this;
+  let self = this;
   async.waterfall([
     function compileContracts(callback) {
-      var compiler = new Compiler({plugins: self.plugins, logger: self.logger});
+      let compiler = new Compiler({plugins: self.plugins, logger: self.logger});
         compiler.compile_contracts(self.contractFiles, function(err, compiledObject) {
           self.compiledContracts = compiledObject;
           callback(err);
         });
     },
     function prepareContractsFromConfig(callback) {
-      var className, contract;
+      let className, contract;
       for(className in self.contractsConfig.contracts) {
         contract = self.contractsConfig.contracts[className];
 
@@ -58,7 +58,7 @@ ContractsManager.prototype.build = function(done) {
       callback();
     },
     function setDeployIntention(callback) {
-      var className, contract;
+      let className, contract;
       for(className in self.contracts) {
         contract = self.contracts[className];
         contract.deploy = (contract.deploy === undefined) || contract.deploy;
@@ -66,7 +66,7 @@ ContractsManager.prototype.build = function(done) {
       callback();
     },
     function prepareContractsFromCompilation(callback) {
-      var className, compiledContract, contractConfig, contract;
+      let className, compiledContract, contractConfig, contract;
       for(className in self.compiledContracts) {
         compiledContract = self.compiledContracts[className];
         contractConfig   = self.contractsConfig.contracts[className];
@@ -94,7 +94,7 @@ ContractsManager.prototype.build = function(done) {
     },
     /*eslint complexity: ["error", 11]*/
     function dealWithSpecialConfigs(callback) {
-      var className, contract, parentContractName, parentContract;
+      let className, contract, parentContractName, parentContract;
 
       for(className in self.contracts) {
         contract = self.contracts[className];
@@ -136,7 +136,7 @@ ContractsManager.prototype.build = function(done) {
       callback();
     },
     function removeContractsWithNoCode(callback) {
-      var className, contract;
+      let className, contract;
       for(className in self.contracts) {
         contract = self.contracts[className];
 
@@ -149,15 +149,15 @@ ContractsManager.prototype.build = function(done) {
       callback();
     },
     function determineDependencies(callback) {
-      var className, contract;
+      let className, contract;
       for(className in self.contracts) {
         contract = self.contracts[className];
 
         if (contract.args === []) continue;
 
-        var ref = contract.args;
-        for (var j = 0; j < ref.length; j++) {
-          var arg = ref[j];
+        let ref = contract.args;
+        for (let j = 0; j < ref.length; j++) {
+          let arg = ref[j];
           if (arg[0] === "$") {
             self.contractDependencies[className] = self.contractDependencies[className] || [];
             self.contractDependencies[className].push(arg.substr(1));
@@ -180,20 +180,20 @@ ContractsManager.prototype.getContract = function(className) {
 };
 
 ContractsManager.prototype.sortContracts = function(contractList) {
-  var converted_dependencies = [], i;
+  let converted_dependencies = [], i;
 
-  for(var contract in this.contractDependencies) {
-    var dependencies = this.contractDependencies[contract];
+  for(let contract in this.contractDependencies) {
+    let dependencies = this.contractDependencies[contract];
     for(i=0; i < dependencies.length; i++) {
       converted_dependencies.push([contract, dependencies[i]]);
     }
   }
 
-  var orderedDependencies = toposort(converted_dependencies).reverse();
+  let orderedDependencies = toposort(converted_dependencies).reverse();
 
-  var newList = contractList.sort(function(a,b) {
-    var order_a = orderedDependencies.indexOf(a.className);
-    var order_b = orderedDependencies.indexOf(b.className);
+  let newList = contractList.sort(function(a,b) {
+    let order_a = orderedDependencies.indexOf(a.className);
+    let order_b = orderedDependencies.indexOf(b.className);
     return order_a - order_b;
   });
 
@@ -202,21 +202,21 @@ ContractsManager.prototype.sortContracts = function(contractList) {
 
 // TODO: should be built contracts
 ContractsManager.prototype.listContracts = function() {
-  var contracts = [];
-  for(var className in this.contracts) {
-    var contract = this.contracts[className];
+  let contracts = [];
+  for(let className in this.contracts) {
+    let contract = this.contracts[className];
     contracts.push(contract);
   }
   return this.sortContracts(contracts);
 };
 
 ContractsManager.prototype.contractsState = function() {
-  var data = [];
+  let data = [];
 
-  for(var className in this.contracts) {
-    var contract = this.contracts[className];
+  for(let className in this.contracts) {
+    let contract = this.contracts[className];
 
-    var contractData;
+    let contractData;
 
     if (contract.deploy === false) {
       contractData = [
diff --git a/lib/contracts/deploy.js b/lib/contracts/deploy.js
index 5e3ae70ac..42c33e47b 100644
--- a/lib/contracts/deploy.js
+++ b/lib/contracts/deploy.js
@@ -1,11 +1,11 @@
-var async = require('async');
+let async = require('async');
 
-var RunCode = require('../core/runCode.js');
+let RunCode = require('../core/runCode.js');
 
-var DeployTracker = require('./deploy_tracker.js');
-var ABIGenerator = require('./abi.js');
+let DeployTracker = require('./deploy_tracker.js');
+let ABIGenerator = require('./abi.js');
 
-var Deploy = function(options) {
+let Deploy = function(options) {
   this.web3 = options.web3;
   this.contractsManager = options.contractsManager;
   this.logger = options.logger;
@@ -17,7 +17,7 @@ var Deploy = function(options) {
 };
 
 Deploy.prototype.determineArguments = function(suppliedArgs) {
-  var realArgs = [], l, arg, contractName, referedContract;
+  let realArgs = [], l, arg, contractName, referedContract;
 
   for (l = 0; l < suppliedArgs.length; l++) {
     arg = suppliedArgs[l];
@@ -34,13 +34,13 @@ Deploy.prototype.determineArguments = function(suppliedArgs) {
 };
 
 Deploy.prototype.checkAndDeployContract = function(contract, params, callback) {
-  var self = this;
-  var suppliedArgs;
-  var realArgs;
-  var arg;
-  var l;
-  var contractName;
-  var referedContract;
+  let self = this;
+  let suppliedArgs;
+  let realArgs;
+  let arg;
+  let l;
+  let contractName;
+  let referedContract;
   contract.error = false;
 
   if (contract.deploy === false) {
@@ -59,7 +59,7 @@ Deploy.prototype.checkAndDeployContract = function(contract, params, callback) {
     return callback();
   }
 
-  var trackedContract = self.deployTracker.getContract(contract.className, contract.realRuntimeBytecode, contract.args);
+  let trackedContract = self.deployTracker.getContract(contract.className, contract.realRuntimeBytecode, contract.args);
 
   if (trackedContract && this.web3.eth.getCode(trackedContract.address) !== "0x") {
     self.logger.info(contract.className.bold.cyan + " already deployed at ".green + trackedContract.address.bold.cyan);
@@ -80,9 +80,9 @@ Deploy.prototype.checkAndDeployContract = function(contract, params, callback) {
 
       if (contract.onDeploy !== undefined) {
         self.logger.info('executing onDeploy commands');
-        var abiGenerator = new ABIGenerator({contractsManager: self.contractsManager});
-        var abi = abiGenerator.generateContracts(false);
-        var cmds = contract.onDeploy.join(';\n');
+        let abiGenerator = new ABIGenerator({contractsManager: self.contractsManager});
+        let abi = abiGenerator.generateContracts(false);
+        let cmds = contract.onDeploy.join(';\n');
 
         RunCode.doEval(abi + "\n" + cmds, self.web3);
       }
@@ -94,10 +94,10 @@ Deploy.prototype.checkAndDeployContract = function(contract, params, callback) {
 };
 
 Deploy.prototype.deployContract = function(contract, params, callback) {
-  var self = this;
-  var contractObject = this.web3.eth.contract(contract.abiDefinition);
+  let self = this;
+  let contractObject = this.web3.eth.contract(contract.abiDefinition);
 
-  var contractParams = (params || contract.args).slice();
+  let contractParams = (params || contract.args).slice();
 
   this.web3.eth.getAccounts(function(err, accounts) {
     if (err) {
@@ -121,7 +121,7 @@ Deploy.prototype.deployContract = function(contract, params, callback) {
 
       if (err) {
         self.logger.error("error deploying contract: " + contract.className.cyan);
-        var errMsg = err.toString();
+        let errMsg = err.toString();
         if (errMsg === 'Error: The contract code couldn\'t be stored, please check your gas amount.') {
           errMsg = 'The contract code couldn\'t be stored, out of gas or constructor error';
         }
@@ -141,7 +141,7 @@ Deploy.prototype.deployContract = function(contract, params, callback) {
 };
 
 Deploy.prototype.deployAll = function(done) {
-  var self = this;
+  let self = this;
   this.logger.info("deploying contracts");
 
   async.eachOfSeries(this.contractsManager.listContracts(),
diff --git a/lib/contracts/deploy_tracker.js b/lib/contracts/deploy_tracker.js
index 79152057d..931a4ee12 100644
--- a/lib/contracts/deploy_tracker.js
+++ b/lib/contracts/deploy_tracker.js
@@ -1,6 +1,6 @@
-var fs = require('../core/fs.js');
+let fs = require('../core/fs.js');
 
-var DeployTracker = function(options) {
+let DeployTracker = function(options) {
   this.logger = options.logger;
   this.env = options.env;
   this.chainConfig = options.chainConfig;
@@ -12,8 +12,8 @@ var DeployTracker = function(options) {
   }
 
   // TODO: need to make this async
-  var block = this.web3.eth.getBlock(0);
-  var chainId = block.hash;
+  let block = this.web3.eth.getBlock(0);
+  let chainId = block.hash;
 
   if (this.chainConfig[chainId] === undefined) {
     this.chainConfig[chainId] = {contracts: {}};
@@ -40,7 +40,7 @@ DeployTracker.prototype.trackContract = function(contractName, code, args, addre
 };
 
 DeployTracker.prototype.getContract = function(contractName, code, args) {
-  var contract = this.currentChain.contracts[this.web3.sha3(code + contractName + args.join(','))];
+  let contract = this.currentChain.contracts[this.web3.sha3(code + contractName + args.join(','))];
   if (contract && contract.address === undefined) { return false; }
   return contract;
 };
diff --git a/lib/contracts/solcP.js b/lib/contracts/solcP.js
index 2332091fd..47cbc98d0 100644
--- a/lib/contracts/solcP.js
+++ b/lib/contracts/solcP.js
@@ -1,4 +1,4 @@
-var solc;
+let solc;
 
 process.on('message', function(msg) {
   if (msg.action === 'loadCompiler') {
@@ -7,7 +7,7 @@ process.on('message', function(msg) {
   }
 
   if (msg.action === 'compile') {
-    var output = solc.compile(msg.obj, msg.optimize);
+    let output = solc.compile(msg.obj, msg.optimize);
     process.send({result: "compilation", output: output});
   }
 });
diff --git a/lib/contracts/solcW.js b/lib/contracts/solcW.js
index e9a0f9ada..e9d980cd1 100644
--- a/lib/contracts/solcW.js
+++ b/lib/contracts/solcW.js
@@ -1,8 +1,8 @@
-var utils = require('../utils/utils.js');
-var solcProcess;
-var compilerLoaded = false;
+let utils = require('../utils/utils.js');
+let solcProcess;
+let compilerLoaded = false;
 
-var SolcW = function() {
+let SolcW = function() {
 };
 
 SolcW.prototype.load_compiler = function(done) {
diff --git a/lib/core/core.js b/lib/core/core.js
index 424eda08c..5632edd25 100644
--- a/lib/core/core.js
+++ b/lib/core/core.js
@@ -1,5 +1,5 @@
 
-var Core = function() {};
+let Core = function() {};
 
 module.exports = Core;
 
diff --git a/lib/core/engine.js b/lib/core/engine.js
index 9f7a87361..e107fadcb 100644
--- a/lib/core/engine.js
+++ b/lib/core/engine.js
@@ -1,20 +1,20 @@
-var http = require('http');
-var Web3 = require('web3');
-var utils = require('../utils/utils.js');
+let http = require('http');
+let Web3 = require('web3');
+let utils = require('../utils/utils.js');
 
-var Events = require('./events.js');
-var Logger = require('./logger.js');
-var Config = require('./config.js');
+let Events = require('./events.js');
+let Logger = require('./logger.js');
+let Config = require('./config.js');
 
-var DeployManager = require('../contracts/deploy_manager.js');
-var ABIGenerator = require('../contracts/abi.js');
-var ServicesMonitor = require('./services_monitor.js');
-var Pipeline = require('../pipeline/pipeline.js');
-var Server = require('../pipeline/server.js');
-var Watch = require('../pipeline/watch.js');
-var version = require('../../package.json').version;
+let DeployManager = require('../contracts/deploy_manager.js');
+let ABIGenerator = require('../contracts/abi.js');
+let ServicesMonitor = require('./services_monitor.js');
+let Pipeline = require('../pipeline/pipeline.js');
+let Server = require('../pipeline/server.js');
+let Watch = require('../pipeline/watch.js');
+let version = require('../../package.json').version;
 
-var Engine = function(options) {
+let Engine = function(options) {
   this.env = options.env;
   this.embarkConfig = options.embarkConfig;
   this.interceptLogs = options.interceptLogs;
@@ -22,8 +22,8 @@ var Engine = function(options) {
 };
 
 Engine.prototype.init = function(_options) {
-  var self = this;
-  var options = _options || {};
+  let self = this;
+  let options = _options || {};
   this.events = new Events();
   this.logger = options.logger || new Logger({logLevel: 'debug'});
   this.config = new Config({env: this.env, logger: this.logger, events: this.events});
@@ -37,9 +37,9 @@ Engine.prototype.init = function(_options) {
 };
 
 Engine.prototype.startMonitor = function() {
-  var self = this;
+  let self = this;
   if (this.plugins) {
-    var servicePlugins = this.plugins.getPluginsFor('serviceChecks');
+    let servicePlugins = this.plugins.getPluginsFor('serviceChecks');
     servicePlugins.forEach(function(plugin) {
       plugin.serviceChecks.forEach(function(pluginCheck) {
         self.servicesMonitor.addCheck(pluginCheck.checkName, pluginCheck.checkFn, pluginCheck.time);
@@ -50,9 +50,9 @@ Engine.prototype.startMonitor = function() {
 };
 
 Engine.prototype.startService = function(serviceName, _options) {
-  var options = _options || {};
+  let options = _options || {};
 
-  var services = {
+  let services = {
     "pipeline":    this.pipelineService,
     "abi":         this.abiService,
     "deployment":  this.deploymentService,
@@ -62,7 +62,7 @@ Engine.prototype.startService = function(serviceName, _options) {
     "web3":        this.web3Service
   };
 
-  var service = services[serviceName];
+  let service = services[serviceName];
 
   if (!service) {
     throw new Error("unknown service: " + serviceName);
@@ -74,9 +74,9 @@ Engine.prototype.startService = function(serviceName, _options) {
 };
 
 Engine.prototype.pipelineService = function(options) {
-  var self = this;
+  let self = this;
   this.logger.setStatus("Building Assets");
-  var pipeline = new Pipeline({
+  let pipeline = new Pipeline({
     buildDir: this.config.buildDir,
     contractsFiles: this.config.contractsFiles,
     assetFiles: this.config.assetFiles,
@@ -100,18 +100,18 @@ Engine.prototype.pipelineService = function(options) {
 };
 
 Engine.prototype.abiService = function(options) {
-  var self = this;
-  var generateABICode = function(contractsManager) {
-    var abiGenerator = new ABIGenerator({
+  let self = this;
+  let generateABICode = function(contractsManager) {
+    let abiGenerator = new ABIGenerator({
       blockchainConfig: self.config.blockchainConfig,
       contractsManager: contractsManager,
       plugins: self.plugins,
       storageConfig: self.config.storageConfig,
       communicationConfig: self.config.communicationConfig
     });
-    var embarkJSABI = abiGenerator.generateABI({useEmbarkJS: true});
-    var vanillaABI = abiGenerator.generateABI({useEmbarkJS: false});
-    var vanillaContractsABI = abiGenerator.generateContracts(false);
+    let embarkJSABI = abiGenerator.generateABI({useEmbarkJS: true});
+    let vanillaABI = abiGenerator.generateABI({useEmbarkJS: false});
+    let vanillaContractsABI = abiGenerator.generateContracts(false);
 
     self.events.emit('abi-contracts-vanila', vanillaContractsABI);
     self.events.emit('abi-vanila', vanillaABI);
@@ -122,7 +122,7 @@ Engine.prototype.abiService = function(options) {
 };
 
 Engine.prototype.deploymentService = function(options) {
-  var self = this;
+  let self = this;
   this.deployManager = new DeployManager({
     web3: options.web3 || self.web3,
     trackContracts: options.trackContracts,
@@ -144,27 +144,27 @@ Engine.prototype.deploymentService = function(options) {
 
 Engine.prototype.fileWatchService = function(options) {
   this.logger.setStatus("Watching for changes");
-  var watch = new Watch({logger: this.logger, events: this.events});
+  let watch = new Watch({logger: this.logger, events: this.events});
   watch.start();
 };
 
 Engine.prototype.webServerService = function(options) {
-  var self = this;
-  var webServerConfig = this.config.webServerConfig;
+  let self = this;
+  let webServerConfig = this.config.webServerConfig;
   if (!webServerConfig.enabled) { return; }
 
-  var host = options.host || webServerConfig.host;
-  var port = options.port  || webServerConfig.port;
+  let host = options.host || webServerConfig.host;
+  let port = options.port  || webServerConfig.port;
 
   this.logger.setStatus("Starting Server");
-  var server = new Server({
+  let server = new Server({
     logger: this.logger,
     host: host,
     port: port
   });
 
   self.servicesMonitor.addCheck('Webserver', function(cb) {
-    var devServer = 'Webserver (http://' + host + ':' + port + ')';
+    let devServer = 'Webserver (http://' + host + ':' + port + ')';
     return cb({name: devServer, status: 'green'});
   });
 
@@ -173,7 +173,7 @@ Engine.prototype.webServerService = function(options) {
 };
 
 Engine.prototype.ipfsService = function(options) {
-  var self = this;
+  let self = this;
   self.servicesMonitor.addCheck('IPFS', function(cb) {
     utils.checkIsAvailable('http://localhost:5001', function(available) {
       if (available) {
@@ -181,13 +181,13 @@ Engine.prototype.ipfsService = function(options) {
         //The URL should also be flexible to accept non-default IPFS url
         self.logger.trace("Checking IPFS version...");
         http.get('http://localhost:5001/api/v0/version', function(res) {
-          var body = '';
+          let body = '';
           res.on('data', function(d) {
             body += d;
           });
           res.on('end', function() {
             try{
-              var parsed = JSON.parse(body);
+              let parsed = JSON.parse(body);
               if(parsed.Version){
                 return cb({name: ("IPFS " + parsed.Version), status: 'green'});
               }
@@ -213,11 +213,11 @@ Engine.prototype.ipfsService = function(options) {
 };
 
 Engine.prototype.web3Service = function(options) {
-  var self = this;
+  let self = this;
   this.web3 = options.web3;
   if (this.web3 === undefined) {
     this.web3 = new Web3();
-    var web3Endpoint = 'http://' + this.config.blockchainConfig.rpcHost + ':' + this.config.blockchainConfig.rpcPort;
+    let web3Endpoint = 'http://' + this.config.blockchainConfig.rpcHost + ':' + this.config.blockchainConfig.rpcPort;
     this.web3.setProvider(new this.web3.providers.HttpProvider(web3Endpoint));
   }
 
diff --git a/lib/core/fs.js b/lib/core/fs.js
index a88816e4d..56d8aefaa 100644
--- a/lib/core/fs.js
+++ b/lib/core/fs.js
@@ -1,5 +1,5 @@
-var fs = require('fs-extra');
-var utils = require('../utils/utils.js');
+let fs = require('fs-extra');
+let utils = require('../utils/utils.js');
 
 function mkdirpSync() {
   return fs.mkdirpSync.apply(fs.mkdirpSync, arguments);
diff --git a/lib/core/logger.js b/lib/core/logger.js
index 442544a70..f8fa4ebad 100644
--- a/lib/core/logger.js
+++ b/lib/core/logger.js
@@ -1,6 +1,6 @@
-var colors = require('colors');
+let colors = require('colors');
 
-var Logger = function(options) {
+let Logger = function(options) {
   this.logLevels = ['error', 'warn', 'info', 'debug', 'trace'];
   this.logLevel    = options.logLevel || 'info';
   this.logFunction = options.logFunction || console.log;
diff --git a/lib/core/runCode.js b/lib/core/runCode.js
index 7134b94af..6c89be039 100644
--- a/lib/core/runCode.js
+++ b/lib/core/runCode.js
@@ -1,5 +1,5 @@
-var Web3 = require('web3');
-var web3;
+let Web3 = require('web3');
+let web3;
 
 // ======================
 // the eval is used for evaluating some of the contact calls for different purposes
diff --git a/lib/core/services_monitor.js b/lib/core/services_monitor.js
index 2685c5c2e..d221f0876 100644
--- a/lib/core/services_monitor.js
+++ b/lib/core/services_monitor.js
@@ -1,9 +1,9 @@
-var async = require('../utils/async_extend.js');
+let async = require('../utils/async_extend.js');
 
 // TODO: need to separate colors from states
 // i.e use status: /on|off|warn/ not /red|green/
 // it's up to the logger or console to determine the color
-var ServicesMonitor = function(options) {
+let ServicesMonitor = function(options) {
   this.events = options.events;
   this.logger = options.logger;
   this.checkList = {};
@@ -13,8 +13,8 @@ var ServicesMonitor = function(options) {
 };
 
 ServicesMonitor.prototype.initCheck = function(checkName) {
-  var self = this;
-  var check = this.checkList[checkName];
+  let self = this;
+  let check = this.checkList[checkName];
 
   if (!check) { return false; }
 
@@ -45,7 +45,7 @@ ServicesMonitor.prototype.initCheck = function(checkName) {
 };
 
 ServicesMonitor.prototype.addCheck = function(checkName, checkFn, time) {
-  var self = this;
+  let self = this;
   this.logger.trace('add check: ' + checkName);
   this.checkList[checkName] = {fn: checkFn, interval: time || 5000};
 
@@ -62,7 +62,7 @@ ServicesMonitor.prototype.stopCheck = function(name) {
 };
 
 ServicesMonitor.prototype.startMonitor = function() {
-  var self = this;
+  let self = this;
   this.working = true;
   this.logger.trace('startMonitor');
 
diff --git a/lib/core/test.js b/lib/core/test.js
index d4b216e45..5117702d0 100644
--- a/lib/core/test.js
+++ b/lib/core/test.js
@@ -1,4 +1,4 @@
-var getSimulator = function() {
+let getSimulator = function() {
   try {
     return require('ethereumjs-testrpc');
   } catch (e) {
@@ -17,18 +17,18 @@ var getSimulator = function() {
   }
 };
 
-var Test;
+let Test;
 Test = (function (options) {
-  var async = require('async');
-  var opts = options === undefined ? {} : options;
+  let async = require('async');
+  let opts = options === undefined ? {} : options;
   opts.logLevel = opts.hasOwnProperty('logLevel') ? opts.logLevel : 'debug';
   opts.simulatorOptions = opts.hasOwnProperty('simulatorOptions') ? opts.simulatorOptions : {};
-  var sim = getSimulator();
+  let sim = getSimulator();
 
   function newWebThree() {
     try {
-      var Web3 = require('web3');
-      var web3 = new Web3();
+      let Web3 = require('web3');
+      let web3 = new Web3();
       web3.setProvider(sim.provider(opts.simulatorOptions));
       return web3;
     } catch (e) {
@@ -37,11 +37,11 @@ Test = (function (options) {
   }
 
   function deployAll(contractsConfig, cb) {
-    var RunCode = require('./runCode.js');
-    var self = this;
+    let RunCode = require('./runCode.js');
+    let self = this;
 
     function newEngine () {
-      var Engine = require('./engine.js');
+      let Engine = require('./engine.js');
       return new Engine({
         env: opts.env || 'test',
         // TODO: confi will need to detect if this is a obj
diff --git a/lib/core/test_logger.js b/lib/core/test_logger.js
index 7795f1a41..d1f8616d4 100644
--- a/lib/core/test_logger.js
+++ b/lib/core/test_logger.js
@@ -1,8 +1,8 @@
-var colors = require('colors');
+let colors = require('colors');
 
 // TODO: just logFunction changes, probably doesn't need a whole new module just
 // for this
-var TestLogger = function(options) {
+let TestLogger = function(options) {
   this.logLevels = ['error', 'warn', 'info', 'debug', 'trace'];
   this.logs = [];
   this.logLevel    = options.logLevel || 'info';
diff --git a/lib/dashboard/command_history.js b/lib/dashboard/command_history.js
index 43e1d2d9d..ba990ba8a 100644
--- a/lib/dashboard/command_history.js
+++ b/lib/dashboard/command_history.js
@@ -1,5 +1,5 @@
 
-var CommandHistory = function() {
+let CommandHistory = function() {
   this.history = [];
   this.pointer = -1;
 };
diff --git a/lib/dashboard/dashboard.js b/lib/dashboard/dashboard.js
index 367b77b85..c3222c247 100644
--- a/lib/dashboard/dashboard.js
+++ b/lib/dashboard/dashboard.js
@@ -1,9 +1,9 @@
-var async = require('async');
+let async = require('async');
 
-var Monitor = require('./monitor.js');
-var Console = require('./console.js');
+let Monitor = require('./monitor.js');
+let Console = require('./console.js');
 
-var Dashboard = function(options) {
+let Dashboard = function(options) {
   this.logger = options.logger;
   this.plugins = options.plugins;
   this.version = options.version;
@@ -11,8 +11,8 @@ var Dashboard = function(options) {
 };
 
 Dashboard.prototype.start = function(done) {
-  var console, monitor;
-  var self = this;
+  let console, monitor;
+  let self = this;
 
   async.waterfall([
     function startConsole(callback) {
diff --git a/lib/dashboard/monitor.js b/lib/dashboard/monitor.js
index b1a243c48..d70f6ce13 100644
--- a/lib/dashboard/monitor.js
+++ b/lib/dashboard/monitor.js
@@ -1,11 +1,11 @@
 /*jshint esversion: 6 */
 
-var blessed = require("blessed");
-var CommandHistory = require('./command_history.js');
-var version = require('../../package.json').version;
+let blessed = require("blessed");
+let CommandHistory = require('./command_history.js');
+let version = require('../../package.json').version;
 
 function Dashboard(options) {
-  var title = (options && options.title) || "Embark " + version;
+  let title = (options && options.title) || "Embark " + version;
   this.env = options.env;
   this.console = options.console;
   this.history = new CommandHistory();
@@ -41,8 +41,8 @@ function Dashboard(options) {
 }
 
 Dashboard.prototype.availableServices = function(_services) {
-  var services = [];
-  var checkName;
+  let services = [];
+  let checkName;
   for (checkName in _services) {
     services.push(_services[checkName]);
   }
@@ -57,7 +57,7 @@ Dashboard.prototype.setStatus = function(status) {
 };
 
 Dashboard.prototype.setContracts = function(contracts) {
-  var data = [];
+  let data = [];
 
   data.push(["Contract Name", "Address", "Status"]);
 
@@ -314,7 +314,7 @@ Dashboard.prototype.layoutCmd = function() {
     }
   });
 
-  var self = this;
+  let self = this;
 
   this.input.key(["C-c"], function() {
     process.exit(0);
@@ -326,13 +326,13 @@ Dashboard.prototype.layoutCmd = function() {
   });
 
   this.input.key(["up"], function() {
-    var cmd = self.history.getPreviousCommand();
+    let cmd = self.history.getPreviousCommand();
     self.input.setValue(cmd);
     self.input.focus();
   });
 
   this.input.key(["down"], function() {
-    var cmd = self.history.getNextCommand();
+    let cmd = self.history.getNextCommand();
     self.input.setValue(cmd);
     self.input.focus();
   });
diff --git a/lib/pipeline/pipeline.js b/lib/pipeline/pipeline.js
index 08016070a..190f22224 100644
--- a/lib/pipeline/pipeline.js
+++ b/lib/pipeline/pipeline.js
@@ -1,7 +1,7 @@
 /*jshint esversion: 6, loopfunc: true */
-var fs = require('../core/fs.js');
+let fs = require('../core/fs.js');
 
-var Pipeline = function(options) {
+let Pipeline = function(options) {
   this.buildDir = options.buildDir;
   this.contractsFiles = options.contractsFiles;
   this.assetFiles = options.assetFiles;
@@ -10,13 +10,13 @@ var Pipeline = function(options) {
 };
 
 Pipeline.prototype.build = function(abi, path) {
-  var self = this;
-  for(var targetFile in this.assetFiles) {
+  let self = this;
+  for(let targetFile in this.assetFiles) {
 
-    var contentFiles = this.assetFiles[targetFile].map(file => {
+    let contentFiles = this.assetFiles[targetFile].map(file => {
       self.logger.trace("reading " + file.filename);
 
-      var pipelinePlugins = this.plugins.getPluginsFor('pipeline');
+      let pipelinePlugins = this.plugins.getPluginsFor('pipeline');
 
       if (file.filename === 'embark.js') {
         return {content: file.content + "\n" + abi, filename: file.filename, path: file.path, modified: true};
@@ -46,27 +46,27 @@ Pipeline.prototype.build = function(abi, path) {
       }
     });
 
-    var dir = targetFile.split('/').slice(0, -1).join('/');
+    let dir = targetFile.split('/').slice(0, -1).join('/');
     self.logger.trace("creating dir " + this.buildDir + dir);
     fs.mkdirpSync(this.buildDir + dir);
 
     // if it's a directory
     if (targetFile.slice(-1) === '/' || targetFile.indexOf('.') === -1) {
-      var targetDir = targetFile;
+      let targetDir = targetFile;
 
       if (targetDir.slice(-1) !== '/') {
         targetDir = targetDir + '/';
       }
 
       contentFiles.map(function(file) {
-        var filename = file.filename.replace('app/', '');
+        let filename = file.filename.replace('app/', '');
         filename = filename.replace(targetDir, '');
         self.logger.info("writing file " + (self.buildDir + targetDir + filename).bold.dim);
 
         fs.copySync(self.buildDir + targetDir + filename, file.path, {overwrite: true});
       });
     } else {
-      var content = contentFiles.map(function(file) {
+      let content = contentFiles.map(function(file) {
         return file.content;
       }).join("\n");
 
diff --git a/lib/pipeline/server.js b/lib/pipeline/server.js
index afbdad2a8..c3b781886 100644
--- a/lib/pipeline/server.js
+++ b/lib/pipeline/server.js
@@ -1,8 +1,8 @@
-var finalhandler = require('finalhandler');
-var http = require('http');
-var serveStatic = require('serve-static');
+let finalhandler = require('finalhandler');
+let http = require('http');
+let serveStatic = require('serve-static');
 
-var Server = function(options) {
+let Server = function(options) {
   this.dist = options.dist || 'dist/';
   this.port = options.port || 8000;
   this.hostname = options.host || 'localhost';
@@ -10,9 +10,9 @@ var Server = function(options) {
 };
 
 Server.prototype.start = function(callback) {
-  var serve = serveStatic(this.dist, {'index': ['index.html', 'index.htm']});
+  let serve = serveStatic(this.dist, {'index': ['index.html', 'index.htm']});
 
-  var server = http.createServer(function onRequest (req, res) {
+  let server = http.createServer(function onRequest (req, res) {
     serve(req, res, finalhandler(req, res));
   });
 
diff --git a/lib/pipeline/watch.js b/lib/pipeline/watch.js
index d1b1c8b79..07a59401a 100644
--- a/lib/pipeline/watch.js
+++ b/lib/pipeline/watch.js
@@ -1,20 +1,20 @@
 /*jshint esversion: 6 */
-var chokidar = require('chokidar');
+let chokidar = require('chokidar');
 
-var fs = require('../core/fs.js');
+let fs = require('../core/fs.js');
 
 // TODO: this should be receiving the config object not re-reading the
 // embark.json file
-var Watch = function(options) {
+let Watch = function(options) {
   this.logger = options.logger;
   this.events = options.events;
 };
 
 Watch.prototype.start = function() {
-   var self = this;
+   let self = this;
   // TODO: should come from the config object instead of reading the file
   // directly
-  var embarkConfig = fs.readJSONSync("embark.json");
+  let embarkConfig = fs.readJSONSync("embark.json");
 
   this.watchAssets(embarkConfig, function() {
     self.logger.trace('ready to watch asset changes');
@@ -32,11 +32,11 @@ Watch.prototype.start = function() {
 };
 
 Watch.prototype.watchAssets = function(embarkConfig, callback) {
-  var self = this;
-  var appConfig = embarkConfig.app;
-  var filesToWatch = [];
+  let self = this;
+  let appConfig = embarkConfig.app;
+  let filesToWatch = [];
 
-  for(var targetFile in appConfig) {
+  for(let targetFile in appConfig) {
     filesToWatch.push(appConfig[targetFile]);
   }
 
@@ -54,7 +54,7 @@ Watch.prototype.watchAssets = function(embarkConfig, callback) {
 };
 
 Watch.prototype.watchContracts = function(embarkConfig, callback) {
-  var self = this;
+  let self = this;
   this.watchFiles(
     [embarkConfig.contracts],
     function(eventName, path) {
@@ -69,7 +69,7 @@ Watch.prototype.watchContracts = function(embarkConfig, callback) {
 };
 
 Watch.prototype.watchConfigs = function(callback) {
-  var self = this;
+  let self = this;
   this.watchFiles(
     "config/**/contracts.json",
     function(eventName, path) {
@@ -87,7 +87,7 @@ Watch.prototype.watchFiles = function(files, changeCallback, doneCallback) {
   this.logger.trace('watchFiles');
   this.logger.trace(files);
 
-  var configWatcher = chokidar.watch(files, {
+  let configWatcher = chokidar.watch(files, {
     ignored: /[\/\\]\./, persistent: true, ignoreInitial: true, followSymlinks: true
   });
 
diff --git a/lib/upload/ipfs.js b/lib/upload/ipfs.js
index 09da3cf46..b21fb7f3c 100644
--- a/lib/upload/ipfs.js
+++ b/lib/upload/ipfs.js
@@ -1,8 +1,8 @@
-var colors = require('colors');
-var async = require('async');
-var shelljs = require('shelljs');
+let colors = require('colors');
+let async = require('async');
+let shelljs = require('shelljs');
 
-var IPFS = function(options) {
+let IPFS = function(options) {
   this.options = options;
   this.buildDir = options.buildDir || 'dist/';
   this.plugins = options.plugins;
@@ -11,10 +11,10 @@ var IPFS = function(options) {
 };
 
 IPFS.prototype.deploy = function() {
-  var self = this;
+  let self = this;
   async.waterfall([
     function findBinary(callback) {
-      var ipfs_bin = shelljs.exec('which ' + self.configIpfsBin).output.split("\n")[0];
+      let ipfs_bin = shelljs.exec('which ' + self.configIpfsBin).output.split("\n")[0];
 
       if (ipfs_bin === 'ipfs not found' || ipfs_bin === ''){
         console.log(('=== WARNING: ' + self.configIpfsBin + ' not found or not in the path. Guessing ~/go/bin/ipfs for path').yellow);
@@ -24,17 +24,17 @@ IPFS.prototype.deploy = function() {
       return callback(null, ipfs_bin);
     },
     function runCommand(ipfs_bin, callback) {
-      var cmd = ipfs_bin + " add -r " + self.buildDir;
+      let cmd = ipfs_bin + " add -r " + self.buildDir;
       console.log(("=== adding " + self.buildDir + " to ipfs").green);
       console.log(cmd.green);
-      var result = shelljs.exec(cmd);
+      let result = shelljs.exec(cmd);
 
       return callback(null, result);
     },
     function getHashFromOutput(result, callback) {
-      var rows = result.output.split("\n");
-      var dir_row = rows[rows.length - 2];
-      var dir_hash = dir_row.split(" ")[1];
+      let rows = result.output.split("\n");
+      let dir_row = rows[rows.length - 2];
+      let dir_hash = dir_row.split(" ")[1];
 
       return callback(null, dir_hash);
     },
diff --git a/lib/upload/swarm.js b/lib/upload/swarm.js
index 667e0e6c9..894c09da3 100644
--- a/lib/upload/swarm.js
+++ b/lib/upload/swarm.js
@@ -1,17 +1,17 @@
-var colors = require('colors');
-var async = require('async');
-var shelljs = require('shelljs');
+let colors = require('colors');
+let async = require('async');
+let shelljs = require('shelljs');
 
-var Swarm = function(options) {
+let Swarm = function(options) {
   this.options = options;
   this.buildDir = options.buildDir || 'dist/';
 };
 
 Swarm.prototype.deploy = function() {
-  var self = this;
+  let self = this;
   async.waterfall([
     function findBinary(callback) {
-      var swarm_bin = shelljs.exec('which swarm').output.split("\n")[0];
+      let swarm_bin = shelljs.exec('which swarm').output.split("\n")[0];
 
       if (swarm_bin==='swarm not found' || swarm_bin === ''){
         console.log('=== WARNING: Swarm not in an executable path. Guessing ~/go/bin/swarm for path'.yellow);
@@ -21,10 +21,10 @@ Swarm.prototype.deploy = function() {
       return callback(null, swarm_bin);
     },
     function runCommand(swarm_bin, callback) {
-      var cmd = swarm_bin + " --defaultpath " + self.buildDir + "index.html --recursive up " + self.buildDir;
+      let cmd = swarm_bin + " --defaultpath " + self.buildDir + "index.html --recursive up " + self.buildDir;
       console.log(("=== adding " + self.buildDir + " to swarm").green);
       console.log(cmd.green);
-      var result = shelljs.exec(cmd);
+      let result = shelljs.exec(cmd);
 
       return callback(null, result);
     },
@@ -33,8 +33,8 @@ Swarm.prototype.deploy = function() {
         return callback("couldn't upload, is the swarm daemon running?");
       }
 
-      var rows = result.output.split("\n");
-      var dir_hash = rows.reverse()[1];
+      let rows = result.output.split("\n");
+      let dir_hash = rows.reverse()[1];
 
       return callback(null, dir_hash);
     },
diff --git a/lib/utils/async_extend.js b/lib/utils/async_extend.js
index 1c6db4f5c..5c024c60a 100644
--- a/lib/utils/async_extend.js
+++ b/lib/utils/async_extend.js
@@ -1,4 +1,4 @@
-var async = require('async');
+let async = require('async');
 
 function asyncEachObject(object, iterator, callback) {
   async.each(
diff --git a/lib/utils/debug_util.js b/lib/utils/debug_util.js
index 9fa0233ff..3bebe506f 100644
--- a/lib/utils/debug_util.js
+++ b/lib/utils/debug_util.js
@@ -6,8 +6,8 @@ function extend(filename, async) {
   }
   async._waterfall = async.waterfall;
   async.waterfall = function(_tasks, callback) {
-    var tasks = _tasks.map(function(t) { 
-      var fn = function() {
+    let tasks = _tasks.map(function(t) {
+      let fn = function() {
         console.log("async " + filename + ": " + t.name);
         t.apply(t, arguments);
       };