diff --git a/libsquoosh/lib/simple-ts.js b/libsquoosh/lib/simple-ts.js
new file mode 100644
index 00000000..98e0d4c9
--- /dev/null
+++ b/libsquoosh/lib/simple-ts.js
@@ -0,0 +1,133 @@
+/**
+ * Copyright 2020 Google Inc. All Rights Reserved.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import { spawn } from 'child_process';
+import { relative, join } from 'path';
+import { promises as fsp } from 'fs';
+import { promisify } from 'util';
+
+import * as ts from 'typescript';
+import glob from 'glob';
+import { sync as whichSync } from 'which';
+
+const globP = promisify(glob);
+
+const tscPath = whichSync('tsc');
+
+const extRe = /\.tsx?$/;
+
+function loadConfig(mainPath) {
+  const fileName = ts.findConfigFile(mainPath, ts.sys.fileExists);
+  if (!fileName) throw Error('tsconfig not found');
+  const text = ts.sys.readFile(fileName);
+  const loadedConfig = ts.parseConfigFileTextToJson(fileName, text).config;
+  const parsedTsConfig = ts.parseJsonConfigFileContent(
+    loadedConfig,
+    ts.sys,
+    process.cwd(),
+    undefined,
+    fileName,
+  );
+  return parsedTsConfig;
+}
+
+export default function simpleTS(mainPath, { noBuild, watch } = {}) {
+  const config = loadConfig(mainPath);
+  const args = ['-b', mainPath];
+
+  let tsBuildDone;
+
+  async function watchBuiltFiles(rollupContext) {
+    const matches = await globP(config.options.outDir + '/**/*.js');
+    for (const match of matches) rollupContext.addWatchFile(match);
+  }
+
+  async function tsBuild(rollupContext) {
+    if (tsBuildDone) {
+      // Watch lists are cleared on each build, so we need to rewatch all the JS files.
+      await watchBuiltFiles(rollupContext);
+      return tsBuildDone;
+    }
+    if (noBuild) {
+      return (tsBuildDone = Promise.resolve());
+    }
+    tsBuildDone = Promise.resolve().then(async () => {
+      await new Promise((resolve) => {
+        const proc = spawn(tscPath, args, {
+          stdio: 'inherit',
+        });
+
+        proc.on('exit', (code) => {
+          if (code !== 0) {
+            throw Error('TypeScript build failed');
+          }
+          resolve();
+        });
+      });
+
+      await watchBuiltFiles(rollupContext);
+
+      if (watch) {
+        tsBuildDone.then(() => {
+          spawn(tscPath, [...args, '--watch', '--preserveWatchOutput'], {
+            stdio: 'inherit',
+          });
+        });
+      }
+    });
+
+    return tsBuildDone;
+  }
+
+  return {
+    name: 'simple-ts',
+    resolveId(id, importer) {
+      // If there isn't an importer, it's an entry point, so we don't need to resolve it relative
+      // to something.
+      if (!importer) return null;
+
+      const tsResolve = ts.resolveModuleName(
+        id,
+        importer,
+        config.options,
+        ts.sys,
+      );
+
+      if (
+        // It didn't find anything
+        !tsResolve.resolvedModule ||
+        // Or if it's linking to a definition file, it's something in node_modules,
+        // or something local like css.d.ts
+        tsResolve.resolvedModule.extension === '.d.ts'
+      ) {
+        return null;
+      }
+      return tsResolve.resolvedModule.resolvedFileName;
+    },
+    async load(id) {
+      if (!extRe.test(id)) return null;
+
+      // TypeScript building is deferred until the first TS file load.
+      // This allows prerequisites to happen first,
+      // such as css.d.ts generation in css-plugin.
+      await tsBuild(this);
+
+      // Look for the JS equivalent in the tmp folder
+      const newId = join(
+        config.options.outDir,
+        relative(config.options.rootDir, id),
+      ).replace(extRe, '.js');
+
+      return fsp.readFile(newId, { encoding: 'utf8' });
+    },
+  };
+}
diff --git a/libsquoosh/package-lock.json b/libsquoosh/package-lock.json
index 3eb66bd2..bd899243 100644
--- a/libsquoosh/package-lock.json
+++ b/libsquoosh/package-lock.json
@@ -1125,9 +1125,9 @@
       "dev": true
     },
     "@types/node": {
-      "version": "15.0.1",
-      "resolved": "https://registry.npmjs.org/@types/node/-/node-15.0.1.tgz",
-      "integrity": "sha512-TMkXt0Ck1y0KKsGr9gJtWGjttxlZnnvDtphxUOSd0bfaR6Q1jle+sPvrzNR1urqYTWMinoKvjKfXUGsumaO1PA==",
+      "version": "15.6.1",
+      "resolved": "https://registry.npmjs.org/@types/node/-/node-15.6.1.tgz",
+      "integrity": "sha512-7EIraBEyRHEe7CH+Fm1XvgqU6uwZN8Q7jppJGcqjROMT29qhAuuOxYB1uEY5UMYQKEmA5D+5tBnhdaPXSsLONA==",
       "dev": true
     },
     "@types/resolve": {
@@ -1492,6 +1492,12 @@
         "@types/estree": "*"
       }
     },
+    "isexe": {
+      "version": "2.0.0",
+      "resolved": "https://registry.npmjs.org/isexe/-/isexe-2.0.0.tgz",
+      "integrity": "sha1-6PvzdNxVb/iUehDcsFctYz8s+hA=",
+      "dev": true
+    },
     "jest-worker": {
       "version": "26.6.2",
       "resolved": "https://registry.npmjs.org/jest-worker/-/jest-worker-26.6.2.tgz",
@@ -1826,6 +1832,12 @@
       "integrity": "sha1-3F5pjL0HkmW8c+A3doGk5Og/YW4=",
       "dev": true
     },
+    "typescript": {
+      "version": "4.3.2",
+      "resolved": "https://registry.npmjs.org/typescript/-/typescript-4.3.2.tgz",
+      "integrity": "sha512-zZ4hShnmnoVnAHpVHWpTcxdv7dWP60S2FsydQLV8V5PbS3FifjWFFRiHSWpDJahly88PRyV5teTSLoq4eG7mKw==",
+      "dev": true
+    },
     "unicode-canonical-property-names-ecmascript": {
       "version": "1.0.4",
       "resolved": "https://registry.npmjs.org/unicode-canonical-property-names-ecmascript/-/unicode-canonical-property-names-ecmascript-1.0.4.tgz",
@@ -1859,6 +1871,15 @@
       "resolved": "https://registry.npmjs.org/web-streams-polyfill/-/web-streams-polyfill-3.0.3.tgz",
       "integrity": "sha512-d2H/t0eqRNM4w2WvmTdoeIvzAUSpK7JmATB8Nr2lb7nQ9BTIJVjbQ/TRFVEh2gUH1HwclPdoPtfMoFfetXaZnA=="
     },
+    "which": {
+      "version": "2.0.2",
+      "resolved": "https://registry.npmjs.org/which/-/which-2.0.2.tgz",
+      "integrity": "sha512-BLI3Tl1TW3Pvl70l3yq3Y64i+awpwXqsGBYWkkqMtnbXgrMD+yj7rhW0kuEDxzJaYXGjEW5ogapKNMEKNMjibA==",
+      "dev": true,
+      "requires": {
+        "isexe": "^2.0.0"
+      }
+    },
     "wrappy": {
       "version": "1.0.2",
       "resolved": "https://registry.npmjs.org/wrappy/-/wrappy-1.0.2.tgz",
diff --git a/libsquoosh/package.json b/libsquoosh/package.json
index bb038b5e..6a333f40 100644
--- a/libsquoosh/package.json
+++ b/libsquoosh/package.json
@@ -22,7 +22,10 @@
     "@rollup/plugin-babel": "^5.3.0",
     "@rollup/plugin-commonjs": "^18.0.0",
     "@rollup/plugin-node-resolve": "^11.2.1",
+    "@types/node": "^15.6.1",
     "rollup": "^2.46.0",
-    "rollup-plugin-terser": "^7.0.2"
+    "rollup-plugin-terser": "^7.0.2",
+    "typescript": "^4.1.3",
+    "which": "^2.0.2"
   }
 }
diff --git a/libsquoosh/rollup.config.js b/libsquoosh/rollup.config.js
index 9c619411..d6d6537d 100644
--- a/libsquoosh/rollup.config.js
+++ b/libsquoosh/rollup.config.js
@@ -1,5 +1,6 @@
 import resolve from '@rollup/plugin-node-resolve';
 import cjs from '@rollup/plugin-commonjs';
+import simpleTS from './lib/simple-ts';
 import asset from './lib/asset-plugin.js';
 import json from './lib/json-plugin.js';
 import autojson from './lib/autojson-plugin.js';
@@ -20,6 +21,7 @@ export default {
     asset(),
     autojson(),
     json(),
+    simpleTS('.'),
     getBabelOutputPlugin({
       babelrc: false,
       configFile: false,
diff --git a/libsquoosh/src/image_data.js b/libsquoosh/src/image_data.js
deleted file mode 100644
index 7d7736be..00000000
--- a/libsquoosh/src/image_data.js
+++ /dev/null
@@ -1,7 +0,0 @@
-export default class ImageData {
-  constructor(data, width, height) {
-    this.data = data;
-    this.width = width;
-    this.height = height;
-  }
-}
diff --git a/libsquoosh/src/image_data.ts b/libsquoosh/src/image_data.ts
new file mode 100644
index 00000000..9125199f
--- /dev/null
+++ b/libsquoosh/src/image_data.ts
@@ -0,0 +1,11 @@
+export default class ImageData {
+  readonly data: Uint8ClampedArray;
+  readonly width: number;
+  readonly height: number;
+
+  constructor(data: Uint8ClampedArray, width: number, height: number) {
+    this.data = data;
+    this.width = width;
+    this.height = height;
+  }
+}
diff --git a/libsquoosh/src/missing-types.d.ts b/libsquoosh/src/missing-types.d.ts
new file mode 100644
index 00000000..09d35510
--- /dev/null
+++ b/libsquoosh/src/missing-types.d.ts
@@ -0,0 +1,178 @@
+/**
+ * Copyright 2020 Google Inc. All Rights Reserved.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+/// <reference path="../../missing-types.d.ts" />
+
+// These don't exist in NodeJS types so we're not able to use them but they are referenced in some emscripten and codec types
+// Thus, we need to explicitly assign them to be `never`
+// We're also not able to use the APIs that use these types
+// So, if we want to use those APIs we need to supply its dependencies ourselves
+// However, probably those APIs are more suited to be used in web (i.e. there can be other
+// dependencies to web APIs that might not work in Node)
+type RequestInfo = never;
+type Response = never;
+type WebGLRenderingContext = never;
+type MessageEvent = never;
+
+type BufferSource = ArrayBufferView | ArrayBuffer;
+type URL = import('url').URL;
+
+/*
+ * Matches the implementation in `image_data.ts` which is exposed to globalThis
+ */
+interface ImageData {
+  /**
+   * Returns the one-dimensional array containing the data in RGBA order, as integers in the range 0 to 255.
+   */
+  readonly data: Uint8ClampedArray;
+  /**
+   * Returns the actual dimensions of the data in the ImageData object, in pixels.
+   */
+  readonly height: number;
+  /**
+   * Returns the actual dimensions of the data in the ImageData object, in pixels.
+   */
+  readonly width: number;
+}
+
+/**
+ * WebAssembly definitions are not available in `@types/node` yet,
+ * so these are copied from `lib.dom.d.ts`
+ */
+declare namespace WebAssembly {
+  interface CompileError {}
+
+  var CompileError: {
+    prototype: CompileError;
+    new (): CompileError;
+  };
+
+  interface Global {
+    value: any;
+    valueOf(): any;
+  }
+
+  var Global: {
+    prototype: Global;
+    new (descriptor: GlobalDescriptor, v?: any): Global;
+  };
+
+  interface Instance {
+    readonly exports: Exports;
+  }
+
+  var Instance: {
+    prototype: Instance;
+    new (module: Module, importObject?: Imports): Instance;
+  };
+
+  interface LinkError {}
+
+  var LinkError: {
+    prototype: LinkError;
+    new (): LinkError;
+  };
+
+  interface Memory {
+    readonly buffer: ArrayBuffer;
+    grow(delta: number): number;
+  }
+
+  var Memory: {
+    prototype: Memory;
+    new (descriptor: MemoryDescriptor): Memory;
+  };
+
+  interface Module {}
+
+  var Module: {
+    prototype: Module;
+    new (bytes: BufferSource): Module;
+    customSections(moduleObject: Module, sectionName: string): ArrayBuffer[];
+    exports(moduleObject: Module): ModuleExportDescriptor[];
+    imports(moduleObject: Module): ModuleImportDescriptor[];
+  };
+
+  interface RuntimeError {}
+
+  var RuntimeError: {
+    prototype: RuntimeError;
+    new (): RuntimeError;
+  };
+
+  interface Table {
+    readonly length: number;
+    get(index: number): Function | null;
+    grow(delta: number): number;
+    set(index: number, value: Function | null): void;
+  }
+
+  var Table: {
+    prototype: Table;
+    new (descriptor: TableDescriptor): Table;
+  };
+
+  interface GlobalDescriptor {
+    mutable?: boolean;
+    value: ValueType;
+  }
+
+  interface MemoryDescriptor {
+    initial: number;
+    maximum?: number;
+  }
+
+  interface ModuleExportDescriptor {
+    kind: ImportExportKind;
+    name: string;
+  }
+
+  interface ModuleImportDescriptor {
+    kind: ImportExportKind;
+    module: string;
+    name: string;
+  }
+
+  interface TableDescriptor {
+    element: TableKind;
+    initial: number;
+    maximum?: number;
+  }
+
+  interface WebAssemblyInstantiatedSource {
+    instance: Instance;
+    module: Module;
+  }
+
+  type ImportExportKind = 'function' | 'global' | 'memory' | 'table';
+  type TableKind = 'anyfunc';
+  type ValueType = 'f32' | 'f64' | 'i32' | 'i64';
+  type ExportValue = Function | Global | Memory | Table;
+  type Exports = Record<string, ExportValue>;
+  type ImportValue = ExportValue | number;
+  type ModuleImports = Record<string, ImportValue>;
+  type Imports = Record<string, ModuleImports>;
+  function compile(bytes: BufferSource): Promise<Module>;
+  // `compileStreaming` does not exist in NodeJS
+  // function compileStreaming(source: Response | Promise<Response>): Promise<Module>;
+  function instantiate(
+    bytes: BufferSource,
+    importObject?: Imports,
+  ): Promise<WebAssemblyInstantiatedSource>;
+  function instantiate(
+    moduleObject: Module,
+    importObject?: Imports,
+  ): Promise<Instance>;
+  // `instantiateStreaming` does not exist in NodeJS
+  // function instantiateStreaming(response: Response | PromiseLike<Response>, importObject?: Imports): Promise<WebAssemblyInstantiatedSource>;
+  function validate(bytes: BufferSource): boolean;
+}
diff --git a/libsquoosh/tsconfig.json b/libsquoosh/tsconfig.json
new file mode 100644
index 00000000..b99cde25
--- /dev/null
+++ b/libsquoosh/tsconfig.json
@@ -0,0 +1,8 @@
+{
+  "extends": "../generic-tsconfig.json",
+  "compilerOptions": {
+    "lib": ["esnext"],
+    "types": ["node"]
+  },
+  "include": ["src/**/*"]
+}