diff --git a/.changeset/hero-dual-quality.md b/.changeset/hero-dual-quality.md
new file mode 100644
index 000000000..5e32ff328
--- /dev/null
+++ b/.changeset/hero-dual-quality.md
@@ -0,0 +1,5 @@
+---
+"nostream-website": minor
+---
+
+Ship the hero film in two qualities: the page serves a high-res render by default and swaps to a low variant for data-saver clients and small screens (navigator.connection.saveData / effectiveType / viewport + DPR pick). build-media.mjs now emits both variants and records both sources in hero.meta.json.
diff --git a/website/site/public/media/hero-low.mp4 b/website/site/public/media/hero-low.mp4
new file mode 100644
index 000000000..4253b25d1
Binary files /dev/null and b/website/site/public/media/hero-low.mp4 differ
diff --git a/website/site/scripts/build-media.mjs b/website/site/scripts/build-media.mjs
index 0c7507db1..de7710391 100644
--- a/website/site/scripts/build-media.mjs
+++ b/website/site/scripts/build-media.mjs
@@ -45,31 +45,57 @@ const landingVideo = [
   path.join(LANDING, 'nostream-hero-low.mp4'),
 ].find((p) => p && existsSync(p))
 
-if (landingVideo) {
-  const filmMeta = readFilmMeta(landingVideo)
-  if (filmMeta?.nipCount == null) {
-    if (existsSync(HERO_META)) unlinkSync(HERO_META)
-    console.error(
-      `build-media: ${landingVideo} has no film.meta.json beside it — re-render in website/hero-animation (pnpm run render) or pick a source that includes meta.`,
-    )
-    process.exit(1)
-  }
+// The low variant ships beside the full one for mobile / Save-Data. It is the
+// previous site video when a fresh high-res render replaces hero.mp4, or the
+// low render when that is all hero-animation has produced.
+const landingLowVideo = [
+  process.env.HERO_LOW_SRC,
+  path.join(LANDING, 'nostream-hero-low.mp4'),
+  landingVideo === path.join(LANDING, 'nostream-hero-low.mp4') ? null : landingVideo,
+].find((p) => p && existsSync(p) && p !== landingVideo)
 
+const encodeHero = (source, outPath, crf) =>
   execFileSync(
     'ffmpeg',
     [
       '-y', '-loglevel', 'error',
-      '-i', landingVideo,
+      '-i', source,
       '-vf', 'unsharp=5:5:0.85:5:5:0.0',
       '-an', '-c:v', 'libx264', '-preset', 'slow', '-pix_fmt', 'yuv420p', '-movflags', '+faststart',
       '-tune', 'animation',
-      '-crf', '15',
-      path.join(MEDIA, 'hero.mp4'),
+      '-crf', String(crf),
+      outPath,
     ],
     { stdio: 'inherit' },
   )
+
+if (landingVideo) {
+  const filmMeta = readFilmMeta(landingVideo)
+  if (filmMeta?.nipCount == null) {
+    if (existsSync(HERO_META)) unlinkSync(HERO_META)
+    console.error(
+      `build-media: ${landingVideo} has no film.meta.json beside it — re-render in website/hero-animation (pnpm run render) or pick a source that includes meta.`,
+    )
+    process.exit(1)
+  }
+
+  encodeHero(landingVideo, path.join(MEDIA, 'hero.mp4'), 15)
   console.log('hero.mp4 ← landing film (film.ts)')
 
+  if (landingLowVideo) {
+    const lowMeta = readFilmMeta(landingLowVideo)
+    if (lowMeta?.nipCount === filmMeta.nipCount) {
+      encodeHero(landingLowVideo, path.join(MEDIA, 'hero-low.mp4'), 22)
+      console.log('hero-low.mp4 ← landing film (low variant)')
+    } else {
+      console.warn(
+        `skip hero-low.mp4: low source meta (${lowMeta?.nipCount}) disagrees with full source (${filmMeta.nipCount}) — regenerate both renders together`,
+      )
+    }
+  } else {
+    console.warn('skip hero-low.mp4: no second source (run `pnpm run render:small` in website/hero-animation)')
+  }
+
   writeFileSync(
     HERO_META,
     `${JSON.stringify(
@@ -77,6 +103,7 @@ if (landingVideo) {
         nipCount: filmMeta.nipCount,
         generatedAt: filmMeta.generatedAt,
         sourceVideo: path.relative(HERO_DIR, landingVideo),
+        ...(landingLowVideo ? { sourceLowVideo: path.relative(HERO_DIR, landingLowVideo) } : {}),
       },
       null,
       2,
diff --git a/website/site/src/components/FilmFrame.astro b/website/site/src/components/FilmFrame.astro
index 4aa3080f3..125cb10e6 100644
--- a/website/site/src/components/FilmFrame.astro
+++ b/website/site/src/components/FilmFrame.astro
@@ -3,15 +3,16 @@ import FilmScreen from './FilmScreen.astro'
 
 interface Props {
   src: string
+  lowSrc?: string
   poster: string
   title: string
   class?: string
 }
-const { src, poster, title, class: className } = Astro.props
+const { src, lowSrc, poster, title, class: className } = Astro.props
 ---
 
 <div class:list={['film-frame', className]}>
-  <FilmScreen src={src} poster={poster} title={title} class="film-crisp" />
+  <FilmScreen src={src} lowSrc={lowSrc} poster={poster} title={title} class="film-crisp" />
 </div>
 
 <style>
diff --git a/website/site/src/components/FilmScreen.astro b/website/site/src/components/FilmScreen.astro
index 5b43794fa..5874b00ea 100644
--- a/website/site/src/components/FilmScreen.astro
+++ b/website/site/src/components/FilmScreen.astro
@@ -3,16 +3,17 @@ import ScreenBar from './ScreenBar.astro'
 
 interface Props {
   src: string
+  lowSrc?: string
   poster: string
   title: string
   class?: string
 }
-const { src, poster, title, class: className } = Astro.props
+const { src, lowSrc, poster, title, class: className } = Astro.props
 ---
 
 <figure class:list={['screen', className]}>
   <ScreenBar title={title} />
-  <video muted loop playsinline preload="auto" poster={poster} data-autoplay aria-label={title}>
+  <video muted loop playsinline preload="auto" poster={poster} data-autoplay data-low-src={lowSrc} aria-label={title}>
     <source src={src} type="video/mp4" />
   </video>
 </figure>
@@ -22,3 +23,31 @@ const { src, poster, title, class: className } = Astro.props
     margin: 0;
   }
 </style>
+
+<script>
+  // Quality pick: swap in the low variant for data-saver clients and small
+  // screens before the browser commits to the full download. The full source
+  // stays the default (the <source> above), so the swap only ever goes down.
+  const setup = (video: HTMLVideoElement) => {
+    const lowSrc = video.dataset.lowSrc
+    if (!lowSrc) return
+    const wantsLow =
+      navigator.connection?.saveData === true ||
+      (navigator.connection?.effectiveType ?? '4g') in { 'slow-2g': 1, '2g': 1, '3g': 1 } ||
+      (matchMedia('(max-width: 768px)').matches && window.devicePixelRatio <= 2)
+    if (!wantsLow) return
+    const source = video.querySelector('source')
+    if (!source) return
+    const time = video.currentTime
+    const wasPlaying = !video.paused
+    source.src = lowSrc
+    video.load()
+    video.currentTime = time
+    if (wasPlaying) void video.play()
+    delete video.dataset.lowSrc
+  }
+  document.querySelectorAll<HTMLVideoElement>('video[data-low-src]').forEach((video) => {
+    if (video.dataset.autoplay != null) setup(video)
+    else video.addEventListener('play', () => setup(video), { once: true })
+  })
+</script>
diff --git a/website/site/src/components/home/Hero.astro b/website/site/src/components/home/Hero.astro
index 0d647ed2e..d9ba89654 100644
--- a/website/site/src/components/home/Hero.astro
+++ b/website/site/src/components/home/Hero.astro
@@ -15,6 +15,7 @@ import { VERSION } from '../../data/site'
   <FilmFrame
     class="hero-film"
     src="/media/hero.mp4"
+    lowSrc="/media/hero-low.mp4"
     poster="/media/hero-poster.webp"
     title={`/hero · nostream ${VERSION}`}
   />