diff --git a/packages/react-base16-styling/.eslintrc.js b/packages/react-base16-styling/.eslintrc.js
index 486b7fd420..fbd5a609c0 100644
--- a/packages/react-base16-styling/.eslintrc.js
+++ b/packages/react-base16-styling/.eslintrc.js
@@ -2,7 +2,7 @@ module.exports = {
   extends: '../../.eslintrc',
   overrides: [
     {
-      files: ['*.ts', '*.tsx'],
+      files: ['*.ts'],
       extends: '../../eslintrc.ts.base.json',
       parserOptions: {
         tsconfigRootDir: __dirname,
@@ -10,7 +10,7 @@ module.exports = {
       },
     },
     {
-      files: ['test/*.ts', 'test/*.tsx'],
+      files: ['test/*.ts'],
       extends: '../../eslintrc.ts.jest.base.json',
       parserOptions: {
         tsconfigRootDir: __dirname,
diff --git a/packages/redux-devtools-dock-monitor/package.json b/packages/redux-devtools-dock-monitor/package.json
index bb54f96d10..d64d5b93ef 100644
--- a/packages/redux-devtools-dock-monitor/package.json
+++ b/packages/redux-devtools-dock-monitor/package.json
@@ -36,7 +36,7 @@
     "lint:fix": "eslint . --ext .ts,.tsx --fix",
     "type-check": "tsc --noEmit",
     "type-check:watch": "npm run type-check -- --watch",
-    "preversion": "npm run type-check && npm run lint && npm run test",
+    "preversion": "npm run type-check && npm run lint",
     "prepublishOnly": "npm run clean && npm run build"
   },
   "dependencies": {
diff --git a/packages/redux-devtools-instrument/.eslintrc.js b/packages/redux-devtools-instrument/.eslintrc.js
index 486b7fd420..fbd5a609c0 100644
--- a/packages/redux-devtools-instrument/.eslintrc.js
+++ b/packages/redux-devtools-instrument/.eslintrc.js
@@ -2,7 +2,7 @@ module.exports = {
   extends: '../../.eslintrc',
   overrides: [
     {
-      files: ['*.ts', '*.tsx'],
+      files: ['*.ts'],
       extends: '../../eslintrc.ts.base.json',
       parserOptions: {
         tsconfigRootDir: __dirname,
@@ -10,7 +10,7 @@ module.exports = {
       },
     },
     {
-      files: ['test/*.ts', 'test/*.tsx'],
+      files: ['test/*.ts'],
       extends: '../../eslintrc.ts.jest.base.json',
       parserOptions: {
         tsconfigRootDir: __dirname,
diff --git a/packages/redux-devtools-instrument/package.json b/packages/redux-devtools-instrument/package.json
index 2d063098e2..59ef2c37e9 100644
--- a/packages/redux-devtools-instrument/package.json
+++ b/packages/redux-devtools-instrument/package.json
@@ -32,8 +32,8 @@
     "build:js": "babel src --out-dir lib --extensions \".ts\" --source-maps inline",
     "clean": "rimraf lib",
     "test": "jest",
-    "lint": "eslint . --ext .ts,.tsx",
-    "lint:fix": "eslint . --ext .ts,.tsx --fix",
+    "lint": "eslint . --ext .ts",
+    "lint:fix": "eslint . --ext .ts --fix",
     "type-check": "tsc --noEmit",
     "type-check:watch": "npm run type-check -- --watch",
     "preversion": "npm run type-check && npm run lint && npm run test",
diff --git a/packages/redux-devtools-log-monitor/package.json b/packages/redux-devtools-log-monitor/package.json
index a4799c6c4d..4c1add2085 100644
--- a/packages/redux-devtools-log-monitor/package.json
+++ b/packages/redux-devtools-log-monitor/package.json
@@ -36,7 +36,7 @@
     "lint:fix": "eslint . --ext .ts,.tsx --fix",
     "type-check": "tsc --noEmit",
     "type-check:watch": "npm run type-check -- --watch",
-    "preversion": "npm run type-check && npm run lint && npm run test",
+    "preversion": "npm run type-check && npm run lint",
     "prepublishOnly": "npm run clean && npm run build"
   },
   "dependencies": {
diff --git a/packages/redux-devtools-serialize/.babelrc b/packages/redux-devtools-serialize/.babelrc
new file mode 100644
index 0000000000..5259cd244f
--- /dev/null
+++ b/packages/redux-devtools-serialize/.babelrc
@@ -0,0 +1,4 @@
+{
+  "presets": ["@babel/preset-env", "@babel/preset-typescript"],
+  "plugins": ["@babel/plugin-proposal-class-properties"]
+}
diff --git a/packages/redux-devtools-serialize/.eslintignore b/packages/redux-devtools-serialize/.eslintignore
new file mode 100644
index 0000000000..a65b41774a
--- /dev/null
+++ b/packages/redux-devtools-serialize/.eslintignore
@@ -0,0 +1 @@
+lib
diff --git a/packages/redux-devtools-serialize/.eslintrc.js b/packages/redux-devtools-serialize/.eslintrc.js
new file mode 100644
index 0000000000..fbd5a609c0
--- /dev/null
+++ b/packages/redux-devtools-serialize/.eslintrc.js
@@ -0,0 +1,21 @@
+module.exports = {
+  extends: '../../.eslintrc',
+  overrides: [
+    {
+      files: ['*.ts'],
+      extends: '../../eslintrc.ts.base.json',
+      parserOptions: {
+        tsconfigRootDir: __dirname,
+        project: ['./tsconfig.json'],
+      },
+    },
+    {
+      files: ['test/*.ts'],
+      extends: '../../eslintrc.ts.jest.base.json',
+      parserOptions: {
+        tsconfigRootDir: __dirname,
+        project: ['./test/tsconfig.json'],
+      },
+    },
+  ],
+};
diff --git a/packages/redux-devtools-serialize/helpers/index.js b/packages/redux-devtools-serialize/helpers/index.js
deleted file mode 100644
index b084c7dbc1..0000000000
--- a/packages/redux-devtools-serialize/helpers/index.js
+++ /dev/null
@@ -1,32 +0,0 @@
-function mark(data, type, transformMethod) {
-  return {
-    data: transformMethod ? data[transformMethod]() : data,
-    __serializedType__: type,
-  };
-}
-
-function extract(data, type) {
-  return {
-    data: Object.assign({}, data),
-    __serializedType__: type,
-  };
-}
-
-function refer(data, type, isArray, refs) {
-  var r = mark(data, type, isArray);
-  if (!refs) return r;
-  for (var i = 0; i < refs.length; i++) {
-    var ref = refs[i];
-    if (typeof ref === 'function' && data instanceof ref) {
-      r.__serializedRef__ = i;
-      return r;
-    }
-  }
-  return r;
-}
-
-module.exports = {
-  mark: mark,
-  extract: extract,
-  refer: refer,
-};
diff --git a/packages/redux-devtools-serialize/immutable/index.js b/packages/redux-devtools-serialize/immutable/index.js
deleted file mode 100644
index 0a9b360d4f..0000000000
--- a/packages/redux-devtools-serialize/immutable/index.js
+++ /dev/null
@@ -1,23 +0,0 @@
-var jsan = require('jsan');
-var serialize = require('./serialize');
-var options = require('../constants/options');
-
-module.exports = function (Immutable, refs, customReplacer, customReviver) {
-  return {
-    stringify: function (data) {
-      return jsan.stringify(
-        data,
-        serialize(Immutable, refs, customReplacer, customReviver).replacer,
-        null,
-        options
-      );
-    },
-    parse: function (data) {
-      return jsan.parse(
-        data,
-        serialize(Immutable, refs, customReplacer, customReviver).reviver
-      );
-    },
-    serialize: serialize,
-  };
-};
diff --git a/packages/redux-devtools-serialize/immutable/serialize.js b/packages/redux-devtools-serialize/immutable/serialize.js
deleted file mode 100644
index eef8e8faa6..0000000000
--- a/packages/redux-devtools-serialize/immutable/serialize.js
+++ /dev/null
@@ -1,87 +0,0 @@
-var helpers = require('../helpers');
-var mark = helpers.mark;
-var extract = helpers.extract;
-var refer = helpers.refer;
-var options = require('../constants/options');
-
-module.exports = function serialize(
-  Immutable,
-  refs,
-  customReplacer,
-  customReviver
-) {
-  function replacer(key, value) {
-    if (value instanceof Immutable.Record)
-      return refer(value, 'ImmutableRecord', 'toObject', refs);
-    if (value instanceof Immutable.Range)
-      return extract(value, 'ImmutableRange');
-    if (value instanceof Immutable.Repeat)
-      return extract(value, 'ImmutableRepeat');
-    if (Immutable.OrderedMap.isOrderedMap(value))
-      return mark(value, 'ImmutableOrderedMap', 'toObject');
-    if (Immutable.Map.isMap(value))
-      return mark(value, 'ImmutableMap', 'toObject');
-    if (Immutable.List.isList(value))
-      return mark(value, 'ImmutableList', 'toArray');
-    if (Immutable.OrderedSet.isOrderedSet(value))
-      return mark(value, 'ImmutableOrderedSet', 'toArray');
-    if (Immutable.Set.isSet(value))
-      return mark(value, 'ImmutableSet', 'toArray');
-    if (Immutable.Seq.isSeq(value))
-      return mark(value, 'ImmutableSeq', 'toArray');
-    if (Immutable.Stack.isStack(value))
-      return mark(value, 'ImmutableStack', 'toArray');
-    return value;
-  }
-
-  function reviver(key, value) {
-    if (
-      typeof value === 'object' &&
-      value !== null &&
-      '__serializedType__' in value
-    ) {
-      var data = value.data;
-      switch (value.__serializedType__) {
-        case 'ImmutableMap':
-          return Immutable.Map(data);
-        case 'ImmutableOrderedMap':
-          return Immutable.OrderedMap(data);
-        case 'ImmutableList':
-          return Immutable.List(data);
-        case 'ImmutableRange':
-          return Immutable.Range(data._start, data._end, data._step);
-        case 'ImmutableRepeat':
-          return Immutable.Repeat(data._value, data.size);
-        case 'ImmutableSet':
-          return Immutable.Set(data);
-        case 'ImmutableOrderedSet':
-          return Immutable.OrderedSet(data);
-        case 'ImmutableSeq':
-          return Immutable.Seq(data);
-        case 'ImmutableStack':
-          return Immutable.Stack(data);
-        case 'ImmutableRecord':
-          return refs && refs[value.__serializedRef__]
-            ? new refs[value.__serializedRef__](data)
-            : Immutable.Map(data);
-        default:
-          return data;
-      }
-    }
-    return value;
-  }
-
-  return {
-    replacer: customReplacer
-      ? function (key, value) {
-          return customReplacer(key, value, replacer);
-        }
-      : replacer,
-    reviver: customReviver
-      ? function (key, value) {
-          return customReviver(key, value, reviver);
-        }
-      : reviver,
-    options: options,
-  };
-};
diff --git a/packages/redux-devtools-serialize/jest.config.js b/packages/redux-devtools-serialize/jest.config.js
new file mode 100644
index 0000000000..8824c11446
--- /dev/null
+++ b/packages/redux-devtools-serialize/jest.config.js
@@ -0,0 +1,3 @@
+module.exports = {
+  preset: 'ts-jest',
+};
diff --git a/packages/redux-devtools-serialize/package.json b/packages/redux-devtools-serialize/package.json
index 06509e12c0..9c8e747436 100644
--- a/packages/redux-devtools-serialize/package.json
+++ b/packages/redux-devtools-serialize/package.json
@@ -2,29 +2,42 @@
   "name": "redux-devtools-serialize",
   "version": "0.1.9",
   "description": "Serialize unserializable data and parse it back.",
-  "main": "index.js",
-  "scripts": {
-    "test": "jest --no-cache",
-    "prepublish": "npm run test"
-  },
-  "repository": {
-    "type": "git",
-    "url": "https://github.com/reduxjs/redux-devtools.git"
-  },
   "keywords": [
     "redux",
     "devtools"
   ],
-  "author": "Mihail Diordiev <zalmoxisus@gmail.com> (https://github.com/zalmoxisus)",
-  "license": "MIT",
+  "homepage": "https://github.com/reduxjs/redux-devtools/tree/master/packages/redux-devtools-serialize",
   "bugs": {
     "url": "https://github.com/reduxjs/redux-devtools/issues"
   },
-  "homepage": "https://github.com/reduxjs/redux-devtools",
-  "devDependencies": {
-    "immutable": "^4.0.0-rc.12"
+  "license": "MIT",
+  "author": "Mihail Diordiev <zalmoxisus@gmail.com> (https://github.com/zalmoxisus)",
+  "main": "lib/index.js",
+  "types": "lib/index.d.ts",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/reduxjs/redux-devtools.git"
+  },
+  "scripts": {
+    "build": "npm run build:types && npm run build:js",
+    "build:types": "tsc --emitDeclarationOnly",
+    "build:js": "babel src --out-dir lib --extensions \".ts\" --source-maps inline",
+    "clean": "rimraf lib",
+    "test": "jest",
+    "lint": "eslint . --ext .ts",
+    "lint:fix": "eslint . --ext .ts --fix",
+    "type-check": "tsc --noEmit",
+    "type-check:watch": "npm run type-check -- --watch",
+    "preversion": "npm run type-check && npm run lint && npm run test",
+    "prepublishOnly": "npm run clean && npm run build"
   },
   "dependencies": {
     "jsan": "^3.1.13"
+  },
+  "devDependencies": {
+    "immutable": "^4.0.0-rc.12"
+  },
+  "peerDependencies": {
+    "immutable": "^4.0.0-rc.12"
   }
 }
diff --git a/packages/redux-devtools-serialize/constants/options.js b/packages/redux-devtools-serialize/src/constants/options.ts
similarity index 93%
rename from packages/redux-devtools-serialize/constants/options.js
rename to packages/redux-devtools-serialize/src/constants/options.ts
index f227a0ceb6..57a8542d3e 100644
--- a/packages/redux-devtools-serialize/constants/options.js
+++ b/packages/redux-devtools-serialize/src/constants/options.ts
@@ -1,6 +1,6 @@
 // jsan stringify options
 
-module.exports = {
+export default {
   refs: false, // references can't be resolved on the original Immutable structure
   date: true,
   function: true,
diff --git a/packages/redux-devtools-serialize/src/helpers/index.ts b/packages/redux-devtools-serialize/src/helpers/index.ts
new file mode 100644
index 0000000000..99076e3b5a
--- /dev/null
+++ b/packages/redux-devtools-serialize/src/helpers/index.ts
@@ -0,0 +1,54 @@
+export interface SerializedData {
+  data: unknown;
+  __serializedType__: string;
+  __serializedRef__?: number;
+}
+
+export function mark(data: unknown, type: string): SerializedData;
+export function mark<K extends string>(
+  data: { [key in K]: () => unknown },
+  type: string,
+  transformMethod?: K | false
+): SerializedData;
+export function mark<K extends string>(
+  data: any,
+  type: string,
+  transformMethod?: 'toString' | false
+): SerializedData;
+export function mark<K extends string>(
+  data: { [key in K]: () => unknown } | unknown,
+  type: string,
+  transformMethod?: K | false
+): SerializedData {
+  return {
+    data: transformMethod
+      ? (data as { [key in K]: () => unknown })[transformMethod]()
+      : data,
+    __serializedType__: type,
+  };
+}
+
+export function extract(data: unknown, type: string): SerializedData {
+  return {
+    data: Object.assign({}, data),
+    __serializedType__: type,
+  };
+}
+
+export function refer<K extends string>(
+  data: { [key in K]: () => unknown },
+  type: string,
+  transformMethod: K | false,
+  refs?: (new (data: any) => unknown)[] | null
+): SerializedData {
+  const r = mark(data, type, transformMethod);
+  if (!refs) return r;
+  for (let i = 0; i < refs.length; i++) {
+    const ref = refs[i];
+    if (typeof ref === 'function' && data instanceof ref) {
+      r.__serializedRef__ = i;
+      return r;
+    }
+  }
+  return r;
+}
diff --git a/packages/redux-devtools-serialize/src/immutable/index.ts b/packages/redux-devtools-serialize/src/immutable/index.ts
new file mode 100644
index 0000000000..b8fd874bc8
--- /dev/null
+++ b/packages/redux-devtools-serialize/src/immutable/index.ts
@@ -0,0 +1,37 @@
+import jsan from 'jsan';
+import Immutable from 'immutable';
+import serialize from './serialize';
+import options from '../constants/options';
+
+export default function (
+  immutable: typeof Immutable,
+  refs?: (new (data: any) => unknown)[] | null,
+  customReplacer?: (
+    key: string,
+    value: unknown,
+    defaultReplacer: (key: string, value: unknown) => unknown
+  ) => unknown,
+  customReviver?: (
+    key: string,
+    value: unknown,
+    defaultReviver: (key: string, value: unknown) => unknown
+  ) => unknown
+) {
+  return {
+    stringify: function (data: unknown) {
+      return jsan.stringify(
+        data,
+        serialize(immutable, refs, customReplacer, customReviver).replacer,
+        undefined,
+        options
+      );
+    },
+    parse: function (data: string) {
+      return jsan.parse(
+        data,
+        serialize(immutable, refs, customReplacer, customReviver).reviver
+      );
+    },
+    serialize: serialize,
+  };
+}
diff --git a/packages/redux-devtools-serialize/src/immutable/serialize.ts b/packages/redux-devtools-serialize/src/immutable/serialize.ts
new file mode 100644
index 0000000000..22de50f2a9
--- /dev/null
+++ b/packages/redux-devtools-serialize/src/immutable/serialize.ts
@@ -0,0 +1,105 @@
+import Immutable, { OrderedSet, Record } from 'immutable';
+import { mark, extract, refer } from '../helpers';
+import options from '../constants/options';
+import { SerializedImmutableData } from '../types';
+
+export default function serialize(
+  immutable: typeof Immutable,
+  refs?: (new (data: any) => unknown)[] | null,
+  customReplacer?: (
+    key: string,
+    value: unknown,
+    defaultReplacer: (key: string, value: unknown) => unknown
+  ) => unknown,
+  customReviver?: (
+    key: string,
+    value: unknown,
+    defaultReviver: (key: string, value: unknown) => unknown
+  ) => unknown
+) {
+  function replacer(key: string, value: unknown) {
+    if (value instanceof immutable.Record)
+      return refer(value as Record<any>, 'ImmutableRecord', 'toObject', refs);
+    if (value instanceof immutable.Range)
+      return extract(value, 'ImmutableRange');
+    if (value instanceof immutable.Repeat)
+      return extract(value, 'ImmutableRepeat');
+    if (immutable.OrderedMap.isOrderedMap(value))
+      return mark(value, 'ImmutableOrderedMap', 'toObject');
+    if (immutable.Map.isMap(value))
+      return mark(value, 'ImmutableMap', 'toObject');
+    if (immutable.List.isList(value))
+      return mark(value, 'ImmutableList', 'toArray');
+    if (immutable.OrderedSet.isOrderedSet(value))
+      return mark(
+        value as OrderedSet<unknown>,
+        'ImmutableOrderedSet',
+        'toArray'
+      );
+    if (immutable.Set.isSet(value))
+      return mark(value, 'ImmutableSet', 'toArray');
+    if (immutable.Seq.isSeq(value))
+      return mark(value, 'ImmutableSeq', 'toArray');
+    if (immutable.Stack.isStack(value))
+      return mark(value, 'ImmutableStack', 'toArray');
+    return value;
+  }
+
+  function reviver(key: string, value: unknown) {
+    if (
+      typeof value === 'object' &&
+      value !== null &&
+      '__serializedType__' in value
+    ) {
+      const immutableValue = value as SerializedImmutableData;
+      switch (immutableValue.__serializedType__) {
+        case 'ImmutableMap':
+          return immutable.Map(immutableValue.data);
+        case 'ImmutableOrderedMap':
+          return immutable.OrderedMap(immutableValue.data);
+        case 'ImmutableList':
+          return immutable.List(immutableValue.data);
+        case 'ImmutableRange':
+          return immutable.Range(
+            immutableValue.data._start,
+            immutableValue.data._end,
+            immutableValue.data._step
+          );
+        case 'ImmutableRepeat':
+          return immutable.Repeat(
+            immutableValue.data._value,
+            immutableValue.data.size
+          );
+        case 'ImmutableSet':
+          return immutable.Set(immutableValue.data);
+        case 'ImmutableOrderedSet':
+          return immutable.OrderedSet(immutableValue.data);
+        case 'ImmutableSeq':
+          return immutable.Seq(immutableValue.data);
+        case 'ImmutableStack':
+          return immutable.Stack(immutableValue.data);
+        case 'ImmutableRecord':
+          return refs && refs[immutableValue.__serializedRef__!]
+            ? new refs[immutableValue.__serializedRef__!](immutableValue.data)
+            : immutable.Map(immutableValue.data);
+        default:
+          return (immutableValue as { data: unknown }).data;
+      }
+    }
+    return value;
+  }
+
+  return {
+    replacer: customReplacer
+      ? function (key: string, value: unknown) {
+          return customReplacer(key, value, replacer);
+        }
+      : replacer,
+    reviver: customReviver
+      ? function (key: string, value: unknown) {
+          return customReviver(key, value, reviver);
+        }
+      : reviver,
+    options: options,
+  };
+}
diff --git a/packages/redux-devtools-serialize/index.js b/packages/redux-devtools-serialize/src/index.ts
similarity index 54%
rename from packages/redux-devtools-serialize/index.js
rename to packages/redux-devtools-serialize/src/index.ts
index 98648daca5..600d22c095 100644
--- a/packages/redux-devtools-serialize/index.js
+++ b/packages/redux-devtools-serialize/src/index.ts
@@ -1,4 +1,4 @@
-var immutable = require('./immutable');
+import immutable from './immutable';
 
 module.exports = {
   immutable: immutable,
diff --git a/packages/redux-devtools-serialize/src/jsan.ts b/packages/redux-devtools-serialize/src/jsan.ts
new file mode 100644
index 0000000000..9b295e7b60
--- /dev/null
+++ b/packages/redux-devtools-serialize/src/jsan.ts
@@ -0,0 +1,30 @@
+declare module 'jsan' {
+  export interface Options {
+    date?: boolean;
+    function?: boolean;
+    regex?: boolean;
+    undefined?: boolean;
+    error?: boolean;
+    symbol?: boolean;
+    map?: boolean;
+    set?: boolean;
+    nan?: boolean;
+    infinity?: boolean;
+    refs?: boolean;
+  }
+
+  export function stringify(
+    value: unknown,
+    replacer?: (
+      key: string,
+      value: unknown
+    ) => unknown | (number | string)[] | null,
+    space?: string | number,
+    _options?: Options | boolean
+  ): string;
+
+  export function parse(
+    text: string,
+    reviver?: (key: string, value: unknown) => unknown
+  ): unknown;
+}
diff --git a/packages/redux-devtools-serialize/src/types.ts b/packages/redux-devtools-serialize/src/types.ts
new file mode 100644
index 0000000000..b30d0a96d2
--- /dev/null
+++ b/packages/redux-devtools-serialize/src/types.ts
@@ -0,0 +1,71 @@
+interface SerializedImmutableMap {
+  data: Record<string, unknown>;
+  __serializedType__: 'ImmutableMap';
+}
+
+interface SerializedImmutableOrderedMap {
+  data: Record<string, unknown>;
+  __serializedType__: 'ImmutableOrderedMap';
+}
+
+interface SerializedImmutableList {
+  data: unknown[];
+  __serializedType__: 'ImmutableList';
+}
+
+interface SerializedImmutableRangeData {
+  _start: number | undefined;
+  _end: number | undefined;
+  _step: number | undefined;
+}
+interface SerializedImmutableRange {
+  data: SerializedImmutableRangeData;
+  __serializedType__: 'ImmutableRange';
+}
+
+interface SerializedImmutableRepeatData {
+  _value: unknown;
+  size: number | undefined;
+}
+interface SerializedImmutableRepeat {
+  data: SerializedImmutableRepeatData;
+  __serializedType__: 'ImmutableRepeat';
+}
+
+interface SerializedImmutableSet {
+  data: unknown[];
+  __serializedType__: 'ImmutableSet';
+}
+
+interface SerializedImmutableOrderedSet {
+  data: unknown[];
+  __serializedType__: 'ImmutableOrderedSet';
+}
+
+interface SerializedImmutableSeq {
+  data: unknown[];
+  __serializedType__: 'ImmutableSeq';
+}
+
+interface SerializedImmutableStack {
+  data: unknown[];
+  __serializedType__: 'ImmutableStack';
+}
+
+interface SerializedImmutableRecord {
+  data: Record<string, unknown>;
+  __serializedType__: 'ImmutableRecord';
+  __serializedRef__?: number;
+}
+
+export type SerializedImmutableData =
+  | SerializedImmutableMap
+  | SerializedImmutableOrderedMap
+  | SerializedImmutableList
+  | SerializedImmutableRange
+  | SerializedImmutableRepeat
+  | SerializedImmutableSet
+  | SerializedImmutableOrderedSet
+  | SerializedImmutableSeq
+  | SerializedImmutableStack
+  | SerializedImmutableRecord;
diff --git a/packages/redux-devtools-serialize/test/__snapshots__/helpers.spec.js.snap b/packages/redux-devtools-serialize/test/__snapshots__/helpers.spec.ts.snap
similarity index 100%
rename from packages/redux-devtools-serialize/test/__snapshots__/helpers.spec.js.snap
rename to packages/redux-devtools-serialize/test/__snapshots__/helpers.spec.ts.snap
diff --git a/packages/redux-devtools-serialize/test/__snapshots__/immutable.spec.js.snap b/packages/redux-devtools-serialize/test/__snapshots__/immutable.spec.ts.snap
similarity index 65%
rename from packages/redux-devtools-serialize/test/__snapshots__/immutable.spec.js.snap
rename to packages/redux-devtools-serialize/test/__snapshots__/immutable.spec.ts.snap
index 115e2115dc..4c460e04d3 100644
--- a/packages/redux-devtools-serialize/test/__snapshots__/immutable.spec.js.snap
+++ b/packages/redux-devtools-serialize/test/__snapshots__/immutable.spec.ts.snap
@@ -1,6 +1,6 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
-exports[`Immutable Nested stringify 1`] = `"{\\"data\\":[[\\"map\\",{\\"data\\":{\\"seq\\":{\\"data\\":[1,2,3,4,5,6,7,8],\\"__serializedType__\\":\\"ImmutableSeq\\"},\\"stack\\":{\\"data\\":[\\"a\\",\\"b\\",\\"c\\"],\\"__serializedType__\\":\\"ImmutableStack\\"}},\\"__serializedType__\\":\\"ImmutableOrderedMap\\"}],[\\"repeat\\",{\\"data\\":{\\"_value\\":\\"hi\\",\\"size\\":100},\\"__serializedType__\\":\\"ImmutableRepeat\\"}]],\\"__serializedType__\\":\\"ImmutableSet\\"}"`;
+exports[`Immutable Nested stringify 1`] = `"{\\"data\\":[{\\"data\\":{\\"map\\":{\\"data\\":{\\"seq\\":{\\"data\\":[1,2,3,4,5,6,7,8],\\"__serializedType__\\":\\"ImmutableSeq\\"},\\"stack\\":{\\"data\\":[\\"a\\",\\"b\\",\\"c\\"],\\"__serializedType__\\":\\"ImmutableStack\\"}},\\"__serializedType__\\":\\"ImmutableOrderedMap\\"},\\"repeat\\":{\\"data\\":{\\"_value\\":\\"hi\\",\\"size\\":100},\\"__serializedType__\\":\\"ImmutableRepeat\\"}},\\"__serializedType__\\":\\"ImmutableRecord\\",\\"__serializedRef__\\":0},{\\"data\\":[10,9,8,7,6,5,4,3,2,1],\\"__serializedType__\\":\\"ImmutableOrderedSet\\"},{\\"data\\":{\\"_start\\":0,\\"_end\\":7,\\"_step\\":1,\\"size\\":7},\\"__serializedType__\\":\\"ImmutableRange\\"}],\\"__serializedType__\\":\\"ImmutableSet\\"}"`;
 
 exports[`Immutable Record stringify 1`] = `"{\\"data\\":{\\"a\\":1,\\"b\\":3},\\"__serializedType__\\":\\"ImmutableRecord\\",\\"__serializedRef__\\":0}"`;
 
diff --git a/packages/redux-devtools-serialize/test/helpers.spec.js b/packages/redux-devtools-serialize/test/helpers.spec.ts
similarity index 61%
rename from packages/redux-devtools-serialize/test/helpers.spec.js
rename to packages/redux-devtools-serialize/test/helpers.spec.ts
index 7df2e933d4..62af59a37d 100644
--- a/packages/redux-devtools-serialize/test/helpers.spec.js
+++ b/packages/redux-devtools-serialize/test/helpers.spec.ts
@@ -1,7 +1,4 @@
-var helpers = require('../helpers');
-var mark = helpers.mark;
-var extract = helpers.extract;
-var refer = helpers.refer;
+import { mark, extract, refer } from '../src/helpers';
 
 describe('Helpers', function () {
   it('mark', function () {
@@ -16,12 +13,12 @@ describe('Helpers', function () {
   });
 
   it('refer', function () {
-    var TestClass = function (data) {
+    const TestClass = function (data: unknown) {
       return data;
     };
-    var testInstance = new TestClass({ testData: 'test' });
+    const testInstance = new (TestClass as any)({ testData: 'test' });
     expect(
-      refer(testInstance, 'testType', false, [TestClass])
+      refer(testInstance, 'testType', false, [TestClass as any])
     ).toMatchSnapshot();
   });
 });
diff --git a/packages/redux-devtools-serialize/test/immutable.spec.js b/packages/redux-devtools-serialize/test/immutable.spec.js
deleted file mode 100644
index d2959c0d84..0000000000
--- a/packages/redux-devtools-serialize/test/immutable.spec.js
+++ /dev/null
@@ -1,148 +0,0 @@
-var Immutable = require('immutable');
-var Serialize = require('../immutable');
-var serialize = Serialize(Immutable);
-var stringify = serialize.stringify;
-var parse = serialize.parse;
-
-var data = {
-  map: Immutable.Map({ a: 1, b: 2, c: 3, d: 4 }),
-  orderedMap: Immutable.OrderedMap({ b: 2, a: 1, c: 3, d: 4 }),
-  list: Immutable.List([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]),
-  range: Immutable.Range(0, 7),
-  repeat: Immutable.Repeat('hi', 100),
-  set: Immutable.Set([10, 9, 8, 7, 6, 5, 4, 3, 2, 1]),
-  orderedSet: Immutable.OrderedSet([10, 9, 8, 7, 6, 5, 4, 3, 2, 1]),
-  seq: Immutable.Seq([1, 2, 3, 4, 5, 6, 7, 8]),
-  stack: Immutable.Stack.of('a', 'b', 'c'),
-};
-
-describe('Immutable', function () {
-  var stringified = {};
-  describe('Stringify', function () {
-    Object.keys(data).forEach(function (key) {
-      it(key, function () {
-        stringified[key] = stringify(data[key]);
-        expect(stringified[key]).toMatchSnapshot();
-      });
-    });
-  });
-
-  describe('Parse', function () {
-    Object.keys(data).forEach(function (key) {
-      it(key, function () {
-        expect(parse(stringified[key])).toEqual(data[key]);
-      });
-    });
-  });
-
-  describe('Record', function () {
-    var ABRecord = Immutable.Record({ a: 1, b: 2 });
-    var myRecord = new ABRecord({ b: 3 });
-
-    var serialize = Serialize(Immutable, [ABRecord]);
-    var stringify = serialize.stringify;
-    var parse = serialize.parse;
-    var stringifiedRecord;
-
-    it('stringify', function () {
-      stringifiedRecord = stringify(myRecord);
-      expect(stringifiedRecord).toMatchSnapshot();
-    });
-
-    it('parse', function () {
-      expect(parse(stringifiedRecord)).toEqual(myRecord);
-    });
-  });
-
-  describe('Nested', function () {
-    var ABRecord = Immutable.Record({
-      map: Immutable.OrderedMap({ seq: data.seq, stack: data.stack }),
-      repeat: data.repeat,
-    });
-    var nestedData = Immutable.Set(ABRecord(), data.orderedSet, data.range);
-
-    var serialize = Serialize(Immutable, [ABRecord]);
-    var stringify = serialize.stringify;
-    var parse = serialize.parse;
-    var stringifiedNested;
-
-    it('stringify', function () {
-      stringifiedNested = stringify(nestedData);
-      expect(stringifiedNested).toMatchSnapshot();
-    });
-
-    it('parse', function () {
-      expect(parse(stringifiedNested)).toEqual(nestedData);
-    });
-  });
-  describe('With references', function () {
-    it('serializes and deserializes', function () {
-      var sharedValue = [];
-      var record = Immutable.Record({
-        prop: sharedValue,
-      });
-
-      var refs = [record];
-
-      var obj = Immutable.Map({
-        fst: new record(),
-        scnd: new record(),
-      });
-
-      var serialized = stringify(
-        obj,
-        Serialize(Immutable, refs).replacer,
-        null,
-        true
-      );
-      var parsed = JSON.parse(serialized);
-
-      var fstProp = parsed.data.fst.data.prop;
-      var scndProp = parsed.data.scnd.data.prop;
-
-      expect(fstProp).toEqual(scndProp);
-      expect(Array.isArray(obj.get('fst').get('prop')));
-    });
-  });
-
-  describe('Custom replacer and reviver functions', function () {
-    var customOneRepresentation = 'one';
-
-    function customReplacer(key, value, defaultReplacer) {
-      if (value === 1) {
-        return { data: customOneRepresentation, __serializedType__: 'number' };
-      }
-      return defaultReplacer(key, value);
-    }
-
-    function customReviver(key, value, defaultReviver) {
-      if (
-        typeof value === 'object' &&
-        value.__serializedType__ === 'number' &&
-        value.data === customOneRepresentation
-      ) {
-        return 1;
-      }
-      return defaultReviver(key, value);
-    }
-
-    var serializeCustom = Serialize(
-      Immutable,
-      null,
-      customReplacer,
-      customReviver
-    );
-
-    Object.keys(data).forEach(function (key) {
-      var stringified = serializeCustom.stringify(data[key]);
-      it(key, function () {
-        var deserialized = serializeCustom.parse(stringified);
-        expect(deserialized).toEqual(data[key]);
-        if (key === 'map' || key === 'orderedMap') {
-          var deserializedDefault = parse(stringified);
-          expect(deserializedDefault.get('a')).toEqual(customOneRepresentation);
-        }
-      });
-    });
-  });
-});
diff --git a/packages/redux-devtools-serialize/test/immutable.spec.ts b/packages/redux-devtools-serialize/test/immutable.spec.ts
new file mode 100644
index 0000000000..7abee11819
--- /dev/null
+++ b/packages/redux-devtools-serialize/test/immutable.spec.ts
@@ -0,0 +1,159 @@
+import Immutable, { Map, OrderedMap } from 'immutable';
+import Serialize from '../src/immutable';
+import { SerializedData } from '../src/helpers';
+const serialize = Serialize(Immutable);
+const stringify = serialize.stringify;
+const parse = serialize.parse;
+
+const data = {
+  map: Immutable.Map({ a: 1, b: 2, c: 3, d: 4 }),
+  orderedMap: Immutable.OrderedMap({ b: 2, a: 1, c: 3, d: 4 }),
+  list: Immutable.List([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]),
+  range: Immutable.Range(0, 7),
+  repeat: Immutable.Repeat('hi', 100),
+  set: Immutable.Set([10, 9, 8, 7, 6, 5, 4, 3, 2, 1]),
+  orderedSet: Immutable.OrderedSet([10, 9, 8, 7, 6, 5, 4, 3, 2, 1]),
+  seq: Immutable.Seq([1, 2, 3, 4, 5, 6, 7, 8]),
+  stack: Immutable.Stack.of('a', 'b', 'c'),
+};
+
+describe('Immutable', function () {
+  const stringified: { [key: string]: string } = {};
+  describe('Stringify', function () {
+    Object.keys(data).forEach(function (key) {
+      it(key, function () {
+        stringified[key] = stringify(data[key as keyof typeof data]);
+        expect(stringified[key]).toMatchSnapshot();
+      });
+    });
+  });
+
+  describe('Parse', function () {
+    Object.keys(data).forEach(function (key) {
+      it(key, function () {
+        expect(parse(stringified[key])).toEqual(data[key as keyof typeof data]);
+      });
+    });
+  });
+
+  describe('Record', function () {
+    const ABRecord = Immutable.Record({ a: 1, b: 2 });
+    const myRecord = new ABRecord({ b: 3 });
+
+    const serialize = Serialize(Immutable, [ABRecord]);
+    const stringify = serialize.stringify;
+    const parse = serialize.parse;
+    let stringifiedRecord: string;
+
+    it('stringify', function () {
+      stringifiedRecord = stringify(myRecord);
+      expect(stringifiedRecord).toMatchSnapshot();
+    });
+
+    it('parse', function () {
+      expect(parse(stringifiedRecord)).toEqual(myRecord);
+    });
+  });
+
+  describe('Nested', function () {
+    const ABRecord = Immutable.Record({
+      map: Immutable.OrderedMap({ seq: data.seq, stack: data.stack }),
+      repeat: data.repeat,
+    });
+    const nestedData = Immutable.Set([ABRecord(), data.orderedSet, data.range]);
+
+    const serialize = Serialize(Immutable, [ABRecord]);
+    const stringify = serialize.stringify;
+    const parse = serialize.parse;
+    let stringifiedNested: string;
+
+    it('stringify', function () {
+      stringifiedNested = stringify(nestedData);
+      expect(stringifiedNested).toMatchSnapshot();
+    });
+
+    it('parse', function () {
+      expect(parse(stringifiedNested)).toEqual(nestedData);
+    });
+  });
+  describe('With references', function () {
+    it('serializes and deserializes', function () {
+      const sharedValue: unknown[] = [];
+      const record = Immutable.Record({
+        prop: sharedValue,
+      });
+
+      const refs = [record];
+
+      const obj = Immutable.Map({
+        fst: new record(),
+        scnd: new record(),
+      });
+
+      const serialize = Serialize(Immutable, refs);
+      const serialized = serialize.stringify(obj);
+      const parsed = JSON.parse(serialized);
+
+      const fstProp = parsed.data.fst.data.prop;
+      const scndProp = parsed.data.scnd.data.prop;
+
+      expect(fstProp).toEqual(scndProp);
+      expect(Array.isArray(obj.get('fst')!.get('prop'))).toBe(true);
+    });
+  });
+
+  describe('Custom replacer and reviver functions', function () {
+    const customOneRepresentation = 'one';
+
+    function customReplacer(
+      key: string,
+      value: unknown,
+      defaultReplacer: (key: string, value: unknown) => unknown
+    ) {
+      if (value === 1) {
+        return { data: customOneRepresentation, __serializedType__: 'number' };
+      }
+      return defaultReplacer(key, value);
+    }
+
+    function customReviver(
+      key: string,
+      value: unknown,
+      defaultReviver: (key: string, value: unknown) => unknown
+    ) {
+      if (
+        typeof value === 'object' &&
+        (value as SerializedData).__serializedType__ === 'number' &&
+        (value as SerializedData).data === customOneRepresentation
+      ) {
+        return 1;
+      }
+      return defaultReviver(key, value);
+    }
+
+    const serializeCustom = Serialize(
+      Immutable,
+      null,
+      customReplacer,
+      customReviver
+    );
+
+    Object.keys(data).forEach(function (key) {
+      const stringified = serializeCustom.stringify(
+        data[key as keyof typeof data]
+      );
+      it(key, function () {
+        const deserialized = serializeCustom.parse(stringified);
+        expect(deserialized).toEqual(data[key as keyof typeof data]);
+        if (key === 'map' || key === 'orderedMap') {
+          const deserializedDefault = parse(stringified);
+          expect(
+            (deserializedDefault as
+              | Map<unknown, unknown>
+              | OrderedMap<unknown, unknown>).get('a')
+          ).toEqual(customOneRepresentation);
+        }
+      });
+    });
+  });
+});
diff --git a/packages/redux-devtools-serialize/test/tsconfig.json b/packages/redux-devtools-serialize/test/tsconfig.json
new file mode 100644
index 0000000000..b55532d20d
--- /dev/null
+++ b/packages/redux-devtools-serialize/test/tsconfig.json
@@ -0,0 +1,4 @@
+{
+  "extends": "../../../tsconfig.base.json",
+  "include": ["../src", "."]
+}
diff --git a/packages/redux-devtools-serialize/tsconfig.json b/packages/redux-devtools-serialize/tsconfig.json
new file mode 100644
index 0000000000..84575cb5f3
--- /dev/null
+++ b/packages/redux-devtools-serialize/tsconfig.json
@@ -0,0 +1,7 @@
+{
+  "extends": "../../tsconfig.base.json",
+  "compilerOptions": {
+    "outDir": "lib"
+  },
+  "include": ["src"]
+}