diff --git a/src/codecs/imagequant/Quantizer.worker.ts b/src/codecs/imagequant/Quantizer.worker.ts
new file mode 100644
index 00000000..7295648b
--- /dev/null
+++ b/src/codecs/imagequant/Quantizer.worker.ts
@@ -0,0 +1,78 @@
+import imagequant from '../../../codecs/imagequant/imagequant';
+// Using require() so TypeScript doesn’t complain about this not being a module.
+const wasmBinaryUrl = require('../../../codecs/imagequant/imagequant.wasm');
+
+// API exposed by wasm module. Details in the codec’s README.
+interface ModuleAPI {
+  version(): number;
+  create_buffer(width: number, height: number): number;
+  destroy_buffer(pointer: number): void;
+  quantize(buffer: number, width: number, height: number, numColors: number, dither: number): void;
+  free_result(): void;
+  get_result_pointer(): number;
+}
+
+export default class ImageQuant {
+  private emscriptenModule: Promise<EmscriptenWasm.Module>;
+  private api: Promise<ModuleAPI>;
+
+  constructor() {
+    this.emscriptenModule = new Promise((resolve) => {
+      const m = imagequant({
+        // Just to be safe, don’t automatically invoke any wasm functions
+        noInitialRun: false,
+        locateFile(url: string): string {
+          // Redirect the request for the wasm binary to whatever webpack gave us.
+          if (url.endsWith('.wasm')) {
+            return wasmBinaryUrl;
+          }
+          return url;
+        },
+        onRuntimeInitialized() {
+          // An Emscripten is a then-able that, for some reason, `then()`s itself,
+          // causing an infite loop when you wrap it in a real promise. Deleting the `then`
+          // prop solves this for now.
+          // See: https://github.com/kripken/emscripten/blob/incoming/src/postamble.js#L129
+          // TODO(surma@): File a bug with Emscripten on this.
+          delete (m as any).then;
+          resolve(m);
+        },
+      });
+    });
+
+    this.api = (async () => {
+      // Not sure why, but TypeScript complains that I am using
+      // `emscriptenModule` before it’s getting assigned, which is clearly not
+      // true :shrug: Using `any`
+      const m = await (this as any).emscriptenModule;
+      return {
+        version: m.cwrap('version', 'number', []),
+        create_buffer: m.cwrap('create_buffer', 'number', ['number', 'number']),
+        destroy_buffer: m.cwrap('destroy_buffer', '', ['number']),
+        quantize: m.cwrap('quantize', '', ['number', 'number', 'number', 'number', 'number']),
+        free_result: m.cwrap('free_result', '', []),
+        get_result_pointer: m.cwrap('get_result_pointer', 'number', []),
+      };
+    })();
+  }
+
+  async quantize(data: ImageData): Promise<ImageData> {
+    const m = await this.emscriptenModule;
+    const api = await this.api;
+
+    const p = api.create_buffer(data.width, data.height);
+    m.HEAP8.set(new Uint8Array(data.data), p);
+    api.quantize(p, data.width, data.height, 256, 1.0);
+    const resultPointer = api.get_result_pointer();
+    const resultView = new Uint8Array(
+      m.HEAP8.buffer,
+      resultPointer,
+      data.width * data.height * 4,
+    );
+    const result = new Uint8ClampedArray(resultView);
+    api.free_result();
+    api.destroy_buffer(p);
+
+    return new ImageData(result, data.width, data.height);
+  }
+}
diff --git a/src/codecs/imagequant/options.tsx b/src/codecs/imagequant/options.tsx
new file mode 100644
index 00000000..a4a6c590
--- /dev/null
+++ b/src/codecs/imagequant/options.tsx
@@ -0,0 +1,330 @@
+// import { h, Component } from 'preact';
+// import { bind } from '../../lib/util';
+// import * as styles from './styles.scss';
+
+// type Props = {
+//   options: EncodeOptions,
+//   onChange(newOptions: EncodeOptions): void,
+// };
+
+// // From kLosslessPresets in config_enc.c
+// // The format is [method, quality].
+// const losslessPresets:[number, number][] = [
+//   [0, 0], [1, 20], [2, 25], [3, 30], [3, 50],
+//   [4, 50], [4, 75], [4, 90], [5, 90], [6, 100],
+// ];
+// const losslessPresetDefault = 6;
+
+// function determineLosslessQuality(quality: number): number {
+//   const index = losslessPresets.findIndex(item => item[1] === quality);
+//   if (index !== -1) return index;
+//   // Quality doesn't match one of the presets.
+//   // This can happen when toggling 'lossless'.
+//   return losslessPresetDefault;
+// }
+
+// /**
+//  * @param field An HTMLInputElement, but the casting is done here to tidy up onChange.
+//  */
+// function fieldCheckedAsNumber(field: any): number {
+//   return Number((field as HTMLInputElement).checked);
+// }
+
+// /**
+//  * @param field An HTMLInputElement, but the casting is done here to tidy up onChange.
+//  */
+// function fieldValueAsNumber(field: any): number {
+//   return Number((field as HTMLInputElement).value);
+// }
+
+// export default class WebPEncoderOptions extends Component<Props, {}> {
+//   @bind
+//   onChange(event: Event) {
+//     const form = (event.currentTarget as HTMLInputElement).closest('form') as HTMLFormElement;
+//     const lossless = fieldCheckedAsNumber(form.lossless);
+//     const losslessPresetInput = (form.lossless_preset as HTMLInputElement);
+
+//     const options: EncodeOptions = {
+//       // Copy over options the form doesn't care about, eg emulate_jpeg_size
+//       ...this.props.options,
+//       // And now stuff from the form:
+//       lossless,
+//       // Special-cased inputs:
+//       // In lossless mode, the quality is derived from the preset.
+//       quality: lossless ?
+//         losslessPresets[Number(losslessPresetInput.value)][1] :
+//         fieldValueAsNumber(form.quality),
+//       // In lossless mode, the method is derived from the preset.
+//       method: lossless ?
+//         losslessPresets[Number(losslessPresetInput.value)][0] :
+//         fieldValueAsNumber(form.method_input),
+//       image_hint: (form.image_hint as HTMLInputElement).checked ?
+//         WebPImageHint.WEBP_HINT_GRAPH :
+//         WebPImageHint.WEBP_HINT_DEFAULT,
+//       // .checked
+//       exact: fieldCheckedAsNumber(form.exact),
+//       alpha_compression: fieldCheckedAsNumber(form.alpha_compression),
+//       autofilter: fieldCheckedAsNumber(form.autofilter),
+//       filter_type: fieldCheckedAsNumber(form.filter_type),
+//       use_sharp_yuv: fieldCheckedAsNumber(form.use_sharp_yuv),
+//       // .value
+//       near_lossless: fieldValueAsNumber(form.near_lossless),
+//       alpha_quality: fieldValueAsNumber(form.alpha_quality),
+//       alpha_filtering: fieldValueAsNumber(form.alpha_filtering),
+//       sns_strength: fieldValueAsNumber(form.sns_strength),
+//       filter_strength: fieldValueAsNumber(form.filter_strength),
+//       filter_sharpness: fieldValueAsNumber(form.filter_sharpness),
+//       pass: fieldValueAsNumber(form.pass),
+//       preprocessing: fieldValueAsNumber(form.preprocessing),
+//       segments: fieldValueAsNumber(form.segments),
+//       partitions: fieldValueAsNumber(form.partitions),
+//     };
+//     this.props.onChange(options);
+//   }
+
+//   private _losslessSpecificOptions(options: EncodeOptions) {
+//     return (
+//       <div>
+//         <label>
+//           Effort:
+//           <input
+//             name="lossless_preset"
+//             type="range"
+//             min="0"
+//             max="9"
+//             value={'' + determineLosslessQuality(options.quality)}
+//             onChange={this.onChange}
+//           />
+//         </label>
+//         <label>
+//           Slight loss:
+//           <input
+//             class={styles.flipRange}
+//             name="near_lossless"
+//             type="range"
+//             min="0"
+//             max="100"
+//             value={'' + options.near_lossless}
+//             onChange={this.onChange}
+//           />
+//         </label>
+//         <label>
+//           {/*
+//             Although there are 3 different kinds of image hint, webp only
+//             seems to do something with the 'graph' type, and I don't really
+//             understand what it does.
+//           */}
+//           <input
+//             name="image_hint"
+//             type="checkbox"
+//             checked={options.image_hint === WebPImageHint.WEBP_HINT_GRAPH}
+//             value={'' + WebPImageHint.WEBP_HINT_GRAPH}
+//             onChange={this.onChange}
+//           />
+//           Discrete tone image (graph, map-tile etc)
+//         </label>
+//       </div>
+//     );
+//   }
+
+//   private _lossySpecificOptions(options: EncodeOptions) {
+//     return (
+//       <div>
+//         <label>
+//           Effort:
+//           <input
+//             name="method_input"
+//             type="range"
+//             min="0"
+//             max="6"
+//             value={'' + options.method}
+//             onChange={this.onChange}
+//           />
+//         </label>
+//         <label>
+//           Quality:
+//           <input
+//             name="quality"
+//             type="range"
+//             min="0"
+//             max="100"
+//             step="0.01"
+//             value={'' + options.quality}
+//             onChange={this.onChange}
+//           />
+//         </label>
+//         <label>
+//           <input
+//             name="alpha_compression"
+//             type="checkbox"
+//             checked={!!options.alpha_compression}
+//             onChange={this.onChange}
+//           />
+//           Compress alpha
+//         </label>
+//         <label>
+//           Alpha quality:
+//           <input
+//             name="alpha_quality"
+//             type="range"
+//             min="0"
+//             max="100"
+//             value={'' + options.alpha_quality}
+//             onChange={this.onChange}
+//           />
+//         </label>
+//         <label>
+//           Alpha filter quality:
+//           <input
+//             name="alpha_filtering"
+//             type="range"
+//             min="0"
+//             max="2"
+//             value={'' + options.alpha_filtering}
+//             onChange={this.onChange}
+//           />
+//         </label>
+//         <label>
+//           Spacial noise shaping:
+//           <input
+//             name="sns_strength"
+//             type="range"
+//             min="0"
+//             max="100"
+//             value={'' + options.sns_strength}
+//             onChange={this.onChange}
+//           />
+//         </label>
+//         <label>
+//           <input
+//             name="autofilter"
+//             type="checkbox"
+//             checked={!!options.autofilter}
+//             onChange={this.onChange}
+//           />
+//           Auto adjust filter strength
+//         </label>
+//         <label>
+//           Filter strength:
+//           <input
+//             name="filter_strength"
+//             type="range"
+//             min="0"
+//             max="100"
+//             disabled={!!options.autofilter}
+//             value={'' + options.filter_strength}
+//             onChange={this.onChange}
+//           />
+//         </label>
+//         <label>
+//           <input
+//             name="filter_type"
+//             type="checkbox"
+//             checked={!!options.filter_type}
+//             onChange={this.onChange}
+//           />
+//           Strong filter
+//         </label>
+//         <label>
+//           Filter sharpness:
+//           <input
+//             class={styles.flipRange}
+//             name="filter_sharpness"
+//             type="range"
+//             min="0"
+//             max="7"
+//             value={'' + options.filter_sharpness}
+//             onChange={this.onChange}
+//           />
+//         </label>
+//         <label>
+//           <input
+//             name="use_sharp_yuv"
+//             type="checkbox"
+//             checked={!!options.use_sharp_yuv}
+//             onChange={this.onChange}
+//           />
+//           Sharp RGB->YUV conversion
+//         </label>
+//         <label>
+//           Passes:
+//           <input
+//             name="pass"
+//             type="range"
+//             min="1"
+//             max="10"
+//             value={'' + options.pass}
+//             onChange={this.onChange}
+//           />
+//         </label>
+//         <label>
+//           Preprocessing type:
+//           <select
+//             name="preprocessing"
+//             value={'' + options.preprocessing}
+//             onChange={this.onChange}
+//           >
+//             <option value="0">None</option>
+//             <option value="1">Segment smooth</option>
+//             <option value="2">Pseudo-random dithering</option>
+//           </select>
+//         </label>
+//         <label>
+//           Segments:
+//           <input
+//             name="segments"
+//             type="range"
+//             min="1"
+//             max="4"
+//             value={'' + options.segments}
+//             onChange={this.onChange}
+//           />
+//         </label>
+//         <label>
+//           Partitions:
+//           <input
+//             name="partitions"
+//             type="range"
+//             min="0"
+//             max="3"
+//             value={'' + options.partitions}
+//             onChange={this.onChange}
+//           />
+//         </label>
+//       </div>
+//     );
+//   }
+
+//   render({ options }: Props) {
+//     // I'm rendering both lossy and lossless forms, as it becomes much easier when
+//     // gathering the data.
+//     return (
+//       <form>
+//         <label>
+//           <input
+//             name="lossless"
+//             type="checkbox"
+//             checked={!!options.lossless}
+//             onChange={this.onChange}
+//           />
+//           Lossless
+//         </label>
+//         <div class={options.lossless ? '' : styles.hide}>
+//           {this._losslessSpecificOptions(options)}
+//         </div>
+//         <div class={options.lossless ? styles.hide : ''}>
+//           {this._lossySpecificOptions(options)}
+//         </div>
+//         <label>
+//           <input
+//             name="exact"
+//             type="checkbox"
+//             checked={!!options.exact}
+//             onChange={this.onChange}
+//           />
+//           Preserve transparent data. Otherwise, pixels with zero alpha will have RGB also zeroed.
+//         </label>
+//       </form>
+//     );
+//   }
+// }
diff --git a/src/codecs/imagequant/quantizer.ts b/src/codecs/imagequant/quantizer.ts
new file mode 100644
index 00000000..522585b5
--- /dev/null
+++ b/src/codecs/imagequant/quantizer.ts
@@ -0,0 +1,7 @@
+import QuantizerWorker from './Quantizer.worker';
+
+export const name = 'Image Quanitzer';
+export async function quantize(data: ImageData): Promise<ImageData> {
+  const quantizer = await new QuantizerWorker();
+  return quantizer.quantize(data);
+}
diff --git a/src/codecs/imagequant/styles.scss b/src/codecs/imagequant/styles.scss
new file mode 100644
index 00000000..cffbc045
--- /dev/null
+++ b/src/codecs/imagequant/styles.scss
@@ -0,0 +1,6 @@
+.flip-range {
+  transform: scaleX(-1);
+}
+.hide {
+  display: none;
+}
diff --git a/src/components/App/index.tsx b/src/components/App/index.tsx
index ba53e53f..dd1e94ce 100644
--- a/src/components/App/index.tsx
+++ b/src/components/App/index.tsx
@@ -8,6 +8,7 @@ import Options from '../Options';
 import { FileDropEvent } from './custom-els/FileDrop';
 import './custom-els/FileDrop';
 
+import * as quantizer from '../../codecs/imagequant/quantizer';
 import * as mozJPEG from '../../codecs/mozjpeg/encoder';
 import * as webP from '../../codecs/webp/encoder';
 import * as identity from '../../codecs/identity/encoder';
@@ -64,18 +65,19 @@ async function compressImage(
   // Special case for identity
   if (encodeData.type === identity.type) return source.file;
 
+  const quantizedSource = await quantizer.quantize(source.data);
   const compressedData = await (() => {
     switch (encodeData.type) {
-      case mozJPEG.type: return mozJPEG.encode(source.data, encodeData.options);
-      case webP.type: return webP.encode(source.data, encodeData.options);
-      case browserPNG.type: return browserPNG.encode(source.data, encodeData.options);
-      case browserJPEG.type: return browserJPEG.encode(source.data, encodeData.options);
-      case browserWebP.type: return browserWebP.encode(source.data, encodeData.options);
-      case browserGIF.type: return browserGIF.encode(source.data, encodeData.options);
-      case browserTIFF.type: return browserTIFF.encode(source.data, encodeData.options);
-      case browserJP2.type: return browserJP2.encode(source.data, encodeData.options);
-      case browserBMP.type: return browserBMP.encode(source.data, encodeData.options);
-      case browserPDF.type: return browserPDF.encode(source.data, encodeData.options);
+      case mozJPEG.type: return mozJPEG.encode(quantizedSource, encodeData.options);
+      case webP.type: return webP.encode(quantizedSource, encodeData.options);
+      case browserPNG.type: return browserPNG.encode(quantizedSource, encodeData.options);
+      case browserJPEG.type: return browserJPEG.encode(quantizedSource, encodeData.options);
+      case browserWebP.type: return browserWebP.encode(quantizedSource, encodeData.options);
+      case browserGIF.type: return browserGIF.encode(quantizedSource, encodeData.options);
+      case browserTIFF.type: return browserTIFF.encode(quantizedSource, encodeData.options);
+      case browserJP2.type: return browserJP2.encode(quantizedSource, encodeData.options);
+      case browserBMP.type: return browserBMP.encode(quantizedSource, encodeData.options);
+      case browserPDF.type: return browserPDF.encode(quantizedSource, encodeData.options);
       default: throw Error(`Unexpected encoder ${JSON.stringify(encodeData)}`);
     }
   })();