diff --git a/dist/jassub.d.ts b/dist/jassub.d.ts
index 8b09b107be84ebde02961eb63637128bfb62f1a9..01f3792bb0e6532d782659b240aeb34e73018534 100644
--- a/dist/jassub.d.ts
+++ b/dist/jassub.d.ts
@@ -24,6 +24,14 @@ export type JASSUBOptions = {
     queryFonts?: 'local' | 'localandremote' | false;
     libassMemoryLimit?: number;
     libassGlyphLimit?: number;
+    /**
+     * The video's native/source resolution, used as libass' storage size. Set
+     * this on adaptive (MSE/HLS) streams — where `video.videoWidth` follows the
+     * currently-decoded rendition — so subtitles keep full quality regardless
+     * of the active bitrate. Defaults to the decoded video size.
+     */
+    videoWidth?: number;
+    videoHeight?: number;
 } & ({
     video: HTMLVideoElement;
     canvas?: HTMLCanvasElement;
@@ -49,6 +57,8 @@ export default class JASSUB {
     _video: HTMLVideoElement | undefined;
     _videoWidth: number;
     _videoHeight: number;
+    _storageWidth: number;
+    _storageHeight: number;
     _videoColorSpace: string | null;
     _canvas: HTMLCanvasElement;
     _ro: ResizeObserver;
diff --git a/dist/jassub.js b/dist/jassub.js
index bbdaa8d4dcb5269617c53652c0702968093dc922..66cfdac4168e004ff9bb047da7e6ee6b53e02ce4 100644
--- a/dist/jassub.js
+++ b/dist/jassub.js
@@ -21,6 +21,13 @@ export default class JASSUB {
     _video;
     _videoWidth = 0;
     _videoHeight = 0;
+    // The video's native/source resolution, used as libass' storage size. On
+    // adaptive (MSE/HLS) streams `video.videoWidth` reports the currently
+    // decoded rendition, which drops with bandwidth and would blur subtitles;
+    // set the `videoWidth`/`videoHeight` options to the stream's real
+    // resolution to keep subtitle quality independent of the active rendition.
+    _storageWidth = 0;
+    _storageHeight = 0;
     _videoColorSpace = null;
     _canvas;
     _ro = new ResizeObserver(async () => {
@@ -41,6 +48,8 @@ export default class JASSUB {
         JASSUB._test();
         this.timeOffset = opts.timeOffset ?? 0;
         this._video = opts.video;
+        this._storageWidth = opts.videoWidth ?? 0;
+        this._storageHeight = opts.videoHeight ?? 0;
         this._canvas = opts.canvas ?? document.createElement('canvas');
         if (this._video && !opts.canvas) {
             this._canvas.className = 'JASSUB';
@@ -119,7 +128,7 @@ export default class JASSUB {
             this._canvas.style.top = videoSize.y + 'px';
             this._canvas.style.left = videoSize.x + 'px';
         }
-        await this.renderer._resizeCanvas(renderWidth, renderHeight, this._videoWidth || renderWidth, this._videoHeight || renderHeight);
+        await this.renderer._resizeCanvas(renderWidth, renderHeight, this._storageWidth || this._videoWidth || renderWidth, this._storageHeight || this._videoHeight || renderHeight);
         if (this._lastDemandTime)
             await this._demandRender(forceRepaint);
     }
diff --git a/src/jassub.ts b/src/jassub.ts
index 65d290d6a5134aca26caf30c1720a2fbbe881430..c5c0596ec0db35b0607124cbb2045d4312c94259 100644
--- a/src/jassub.ts
+++ b/src/jassub.ts
@@ -37,6 +37,14 @@ export type JASSUBOptions = {
   queryFonts?: 'local' | 'localandremote' | false
   libassMemoryLimit?: number
   libassGlyphLimit?: number
+  /**
+   * The video's native/source resolution, used as libass' storage size. Set
+   * this on adaptive (MSE/HLS) streams — where `video.videoWidth` follows the
+   * currently-decoded rendition — so subtitles keep full quality regardless of
+   * the active bitrate. Defaults to the decoded video size.
+   */
+  videoWidth?: number
+  videoHeight?: number
 } & ({
   video: HTMLVideoElement
   canvas?: HTMLCanvasElement
@@ -63,6 +71,13 @@ export default class JASSUB {
   _video
   _videoWidth = 0
   _videoHeight = 0
+  // The video's native/source resolution, used as libass' storage size. On
+  // adaptive (MSE/HLS) streams `video.videoWidth` reports the currently
+  // decoded rendition, which drops with bandwidth and would blur subtitles;
+  // set the `videoWidth`/`videoHeight` options to the stream's real
+  // resolution to keep subtitle quality independent of the active rendition.
+  _storageWidth = 0
+  _storageHeight = 0
   _videoColorSpace: string | null = null
   _canvas
   _ro = new ResizeObserver(async () => {
@@ -83,6 +98,8 @@ export default class JASSUB {
 
     this.timeOffset = opts.timeOffset ?? 0
     this._video = opts.video
+    this._storageWidth = opts.videoWidth ?? 0
+    this._storageHeight = opts.videoHeight ?? 0
     this._canvas = opts.canvas ?? document.createElement('canvas')
     if (this._video && !opts.canvas) {
       this._canvas.className = 'JASSUB'
@@ -183,8 +200,8 @@ export default class JASSUB {
     await this.renderer._resizeCanvas(
       renderWidth,
       renderHeight,
-      this._videoWidth || renderWidth,
-      this._videoHeight || renderHeight
+      this._storageWidth || this._videoWidth || renderWidth,
+      this._storageHeight || this._videoHeight || renderHeight
     )
 
     if (this._lastDemandTime) await this._demandRender(forceRepaint)