diff --git a/src/analysis/weights.js b/src/analysis/weights.js
index 6e734a7..8f589b4 100644
--- a/src/analysis/weights.js
+++ b/src/analysis/weights.js
@@ -1,6 +1,8 @@
 // @flow
 
+import * as MapUtil from "../util/map";
 import {type NodeAddressT, type EdgeAddressT} from "../core/graph";
+import {toCompat, fromCompat, type Compatible} from "../util/compat";
 
 /**
  * Represents the weight for a particular Node (or NodeType).
@@ -45,3 +47,30 @@ export function defaultWeights(): Weights {
     nodeManualWeights: new Map(),
   };
 }
+
+export type WeightsJSON = Compatible<{|
+  +nodeTypeWeights: {[NodeAddressT]: NodeWeight},
+  +edgeTypeWeights: {[EdgeAddressT]: EdgeWeight},
+  +nodeManualWeights: {[NodeAddressT]: NodeWeight},
+|}>;
+const COMPAT_INFO = {type: "sourcecred/weights", version: "0.1.0"};
+
+export function toJSON(weights: Weights): WeightsJSON {
+  return toCompat(COMPAT_INFO, {
+    nodeTypeWeights: MapUtil.toObject(weights.nodeTypeWeights),
+    edgeTypeWeights: MapUtil.toObject(weights.edgeTypeWeights),
+    nodeManualWeights: MapUtil.toObject(weights.nodeManualWeights),
+  });
+}
+
+export function fromJSON(json: WeightsJSON): Weights {
+  const {nodeTypeWeights, edgeTypeWeights, nodeManualWeights} = fromCompat(
+    COMPAT_INFO,
+    json
+  );
+  return {
+    nodeTypeWeights: MapUtil.fromObject(nodeTypeWeights),
+    edgeTypeWeights: MapUtil.fromObject(edgeTypeWeights),
+    nodeManualWeights: MapUtil.fromObject(nodeManualWeights),
+  };
+}
diff --git a/src/analysis/weights.test.js b/src/analysis/weights.test.js
new file mode 100644
index 0000000..14bd91a
--- /dev/null
+++ b/src/analysis/weights.test.js
@@ -0,0 +1,67 @@
+// @flow
+
+import stringify from "json-stable-stringify";
+import {NodeAddress, EdgeAddress} from "../core/graph";
+import {toJSON, fromJSON, defaultWeights} from "./weights";
+
+describe("analysis/weights", () => {
+  describe("toJSON/fromJSON", () => {
+    it("works for the default weights", () => {
+      const weights = defaultWeights();
+      const json = toJSON(weights);
+      const jsonString = stringify(json, {space: 4});
+      expect(jsonString).toMatchInlineSnapshot(`
+"[
+    {
+        \\"type\\": \\"sourcecred/weights\\",
+        \\"version\\": \\"0.1.0\\"
+    },
+    {
+        \\"edgeTypeWeights\\": {
+        },
+        \\"nodeManualWeights\\": {
+        },
+        \\"nodeTypeWeights\\": {
+        }
+    }
+]"
+`);
+      expect(weights).toEqual(fromJSON(json));
+    });
+
+    it("works for non-default weights", () => {
+      const weights = defaultWeights();
+      weights.nodeTypeWeights.set(NodeAddress.empty, 32);
+      weights.edgeTypeWeights.set(EdgeAddress.empty, {
+        forwards: 7,
+        backwards: 9,
+      });
+      weights.nodeManualWeights.set(NodeAddress.fromParts(["foo"]), 42);
+      const json = toJSON(weights);
+      const jsonString = stringify(json, {space: 4});
+      expect(jsonString).toMatchInlineSnapshot(`
+"[
+    {
+        \\"type\\": \\"sourcecred/weights\\",
+        \\"version\\": \\"0.1.0\\"
+    },
+    {
+        \\"edgeTypeWeights\\": {
+            \\"E\\\\u0000\\": {
+                \\"backwards\\": 9,
+                \\"forwards\\": 7
+            }
+        },
+        \\"nodeManualWeights\\": {
+            \\"N\\\\u0000foo\\\\u0000\\": 42
+        },
+        \\"nodeTypeWeights\\": {
+            \\"N\\\\u0000\\": 32
+        }
+    }
+]"
+`);
+      expect(weights).toEqual(fromJSON(json));
+    });
+  });
+});