diff --git a/package.json b/package.json
index 45857e99..1c470b2c 100644
--- a/package.json
+++ b/package.json
@@ -94,6 +94,7 @@
     "markdown-it-sub": "~1.0.0",
     "markdown-it-sup": "~1.0.0",
     "markdown-pdf": "~9.0.0",
+    "markdownlint": "^0.16.0",
     "mathjax": "~2.7.5",
     "mattermost-redux": "~5.13.0",
     "mermaid": "~8.2.3",
diff --git a/public/images/lint/mark-error.png b/public/images/lint/mark-error.png
new file mode 100644
index 00000000..045901da
Binary files /dev/null and b/public/images/lint/mark-error.png differ
diff --git a/public/images/lint/mark-multiple.png b/public/images/lint/mark-multiple.png
new file mode 100644
index 00000000..8af299b6
Binary files /dev/null and b/public/images/lint/mark-multiple.png differ
diff --git a/public/images/lint/mark-warning.png b/public/images/lint/mark-warning.png
new file mode 100644
index 00000000..d7f28bf6
Binary files /dev/null and b/public/images/lint/mark-warning.png differ
diff --git a/public/images/lint/message-error.png b/public/images/lint/message-error.png
new file mode 100644
index 00000000..8c3ca42f
Binary files /dev/null and b/public/images/lint/message-error.png differ
diff --git a/public/images/lint/message-warning.png b/public/images/lint/message-warning.png
new file mode 100644
index 00000000..07472d04
Binary files /dev/null and b/public/images/lint/message-warning.png differ
diff --git a/public/js/lib/editor/index.js b/public/js/lib/editor/index.js
index 291dd0a4..37257871 100644
--- a/public/js/lib/editor/index.js
+++ b/public/js/lib/editor/index.js
@@ -3,6 +3,7 @@ import * as utils from './utils'
 import config from './config'
 import statusBarTemplate from './statusbar.html'
 import toolBarTemplate from './toolbar.html'
+import './markdown-lint'
 
 /* config section */
 const isMac = CodeMirror.keyMap.default === CodeMirror.keyMap.macDefault
@@ -552,6 +553,7 @@ export default class Editor {
     this.editor = CodeMirror.fromTextArea(textit, {
       mode: defaultEditorMode,
       backdrop: defaultEditorMode,
+      lint: true,
       keyMap: 'sublime',
       viewportMargin: viewportMargin,
       styleActiveLine: true,
@@ -573,7 +575,8 @@ export default class Editor {
       gutters: [
         'CodeMirror-linenumbers',
         'authorship-gutters',
-        'CodeMirror-foldgutter'
+        'CodeMirror-foldgutter',
+        'CodeMirror-lint-markers'
       ],
       extraKeys: this.defaultExtraKeys,
       flattenSpans: true,
diff --git a/public/js/lib/editor/markdown-lint/index.js b/public/js/lib/editor/markdown-lint/index.js
new file mode 100644
index 00000000..ea4bd778
--- /dev/null
+++ b/public/js/lib/editor/markdown-lint/index.js
@@ -0,0 +1,42 @@
+import markdownlint from 'markdownlint'
+
+// load lint plugin explicitly
+import 'script-loader!@hackmd/codemirror/addon/lint/lint'
+import './lint.css'
+
+(function(mod) {
+  mod(CodeMirror);
+})(function(CodeMirror) {
+  function validator(text, options) {
+    return lint(text).map(error => {
+      const lineNumber = error.lineNumber - 1
+
+      let start, end
+      if (error.errorRange) {
+        start = error.errorRange[0] - 1
+        end = error.errorRange[1] - 1
+      } else {
+        start = 0
+        end = -1
+      }
+
+      return {
+        message: error.ruleDescription,
+        severity: 'error',
+        from: CodeMirror.Pos(lineNumber, start),
+        to: CodeMirror.Pos(lineNumber, end)
+      }
+    })
+  }
+
+  CodeMirror.registerHelper('lint', 'markdown', validator);
+});
+
+function lint (content) {
+  const { content: errors } = markdownlint.sync({
+    strings: {
+      content
+    }
+  })
+  return errors
+}
diff --git a/public/js/lib/editor/markdown-lint/lint.css b/public/js/lib/editor/markdown-lint/lint.css
new file mode 100644
index 00000000..d474419a
--- /dev/null
+++ b/public/js/lib/editor/markdown-lint/lint.css
@@ -0,0 +1,72 @@
+/* The lint marker gutter */
+.CodeMirror-lint-markers {
+  width: 16px;
+}
+
+.CodeMirror-lint-tooltip {
+  background-color: #ffd;
+  border: 1px solid black;
+  border-radius: 4px 4px 4px 4px;
+  color: black;
+  font-family: monospace;
+  font-size: 10pt;
+  overflow: hidden;
+  padding: 2px 5px;
+  position: fixed;
+  white-space: pre;
+  white-space: pre-wrap;
+  z-index: 100;
+  max-width: 600px;
+  opacity: 0;
+  transition: opacity .4s;
+  -moz-transition: opacity .4s;
+  -webkit-transition: opacity .4s;
+  -o-transition: opacity .4s;
+  -ms-transition: opacity .4s;
+}
+
+.CodeMirror-lint-mark-error, .CodeMirror-lint-mark-warning {
+  background-position: left bottom;
+  background-repeat: repeat-x;
+}
+
+.CodeMirror-lint-mark-error {
+  background-image: url(/images/lint/mark-error.png);
+  ;
+}
+
+.CodeMirror-lint-mark-warning {
+  background-image: url(/images/lint/mark-warning.png);
+}
+
+.CodeMirror-lint-marker-error, .CodeMirror-lint-marker-warning {
+  background-position: center center;
+  background-repeat: no-repeat;
+  cursor: pointer;
+  display: inline-block;
+  height: 16px;
+  width: 16px;
+  vertical-align: middle;
+  position: relative;
+}
+
+.CodeMirror-lint-message-error, .CodeMirror-lint-message-warning {
+  padding-left: 18px;
+  background-position: top left;
+  background-repeat: no-repeat;
+}
+
+.CodeMirror-lint-marker-error, .CodeMirror-lint-message-error {
+  background-image: url(/images/lint/message-error.png);
+}
+
+.CodeMirror-lint-marker-warning, .CodeMirror-lint-message-warning {
+  background-image: url(/images/lint/message-warning.png);
+}
+
+.CodeMirror-lint-marker-multiple {
+  background-image: url(/images/lint/mark-multiple.png);
+  background-repeat: no-repeat;
+  background-position: right bottom;
+  width: 100%; height: 100%;
+}
diff --git a/public/js/url.js b/public/js/url.js
new file mode 100644
index 00000000..22ed110b
--- /dev/null
+++ b/public/js/url.js
@@ -0,0 +1 @@
+exports.URL = window.URL
diff --git a/webpack.common.js b/webpack.common.js
index a7fe2b86..cd5b5338 100644
--- a/webpack.common.js
+++ b/webpack.common.js
@@ -167,7 +167,11 @@ module.exports = {
         to: 'reveal.js/plugin'
       }
     ]),
-    new MiniCssExtractPlugin()
+    new MiniCssExtractPlugin(),
+    new webpack.NormalModuleReplacementPlugin(
+      /^url$/,
+      path.resolve(__dirname, './public/js/url.js')
+    )
   ],
 
   entry: {
@@ -374,7 +378,8 @@ module.exports = {
       'js-sequence-diagrams': path.join(__dirname, 'node_modules/@hackmd/js-sequence-diagrams/build/main.js'),
       vega: path.join(__dirname, 'node_modules/vega/build/vega.min.js'),
       'vega-lite': path.join(__dirname, 'node_modules/vega-lite/build/vega-lite.min.js'),
-      'vega-embed': path.join(__dirname, 'node_modules/vega-embed/build/vega-embed.min.js')
+      'vega-embed': path.join(__dirname, 'node_modules/vega-embed/build/vega-embed.min.js'),
+      'markdown-it': path.join(__dirname, 'node_modules/markdown-it/dist/markdown-it.js')
     }
   },
 
diff --git a/yarn.lock b/yarn.lock
index 6db3a214..7a708b09 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -7890,7 +7890,7 @@ markdown-it-sup@~1.0.0:
   resolved "https://registry.yarnpkg.com/markdown-it-sup/-/markdown-it-sup-1.0.0.tgz#cb9c9ff91a5255ac08f3fd3d63286e15df0a1fc3"
   integrity sha1-y5yf+RpSVawI8/09YyhuFd8KH8M=
 
-markdown-it@~9.0.1:
+markdown-it@9.0.1, markdown-it@~9.0.1:
   version "9.0.1"
   resolved "https://registry.yarnpkg.com/markdown-it/-/markdown-it-9.0.1.tgz#aafe363c43718720b6575fd10625cde6e4ff2d47"
   integrity sha512-XC9dMBHg28Xi7y5dPuLjM61upIGPJG8AiHNHYqIaXER2KNnn7eKnM5/sF0ImNnyoV224Ogn9b1Pck8VH4k0bxw==
@@ -7921,6 +7921,13 @@ markdown-table@^1.1.0:
   resolved "https://registry.yarnpkg.com/markdown-table/-/markdown-table-1.1.3.tgz#9fcb69bcfdb8717bfd0398c6ec2d93036ef8de60"
   integrity sha512-1RUZVgQlpJSPWYbFSpmudq5nHY1doEIv89gBtF0s4gW1GF2XorxcA/70M5vq7rLv0a6mhOUccRsqkwhwLCIQ2Q==
 
+markdownlint@^0.16.0:
+  version "0.16.0"
+  resolved "https://registry.yarnpkg.com/markdownlint/-/markdownlint-0.16.0.tgz#69f73cc755a44231fbe5dc7c37a5909cedc0ac6e"
+  integrity sha512-Zo+iPezP3eM6lLhKepkUw+X98H44lipIdx4d6faaugfB0+7VuDB3R0hXmx7z9F1N3/ypn46oOFgAD9iF++Ie6A==
+  dependencies:
+    markdown-it "9.0.1"
+
 marked@~0.6.2:
   version "0.6.3"
   resolved "https://registry.yarnpkg.com/marked/-/marked-0.6.3.tgz#79babad78af638ba4d522a9e715cdfdd2429e946"