250 Animated Themes & Dark Modes for ChatGPT and Claude: Vellum

Transform ChatGPT and Claude with 250 hand-built animated backgrounds, from pure black to neon cities. Free trial, no tracking.

Vellum turns ChatGPT and Claude into something worth looking at. Most theme extensions just recolour the page. Vellum gives you 250 hand-built ANIMATED backgrounds — starfields that drift, koi gliding under lily pads, a black hole pulling matter into its accretion disk, neon grids racing to the horizon, a starling flock turning over a dusk field, and a whole arcade of playable-looking classics. They move. Quietly, in the background, while you work. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 250 THEMES, ORGANISED ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Browse by category instead of endless scrolling: ★ Retro — 35 ★ Nature — 23 ★ Space — 22 ★ Abstract — 21 ★ Minimal — 19 ★ Weather — 19 ★ City — 18 ★ Ambient — 17 ★ Geometric — 16 ★ Fire — 15 ★ Seasonal — 15 ★ Audio — 15 ★ Cyber — 15 Search by name, by category, or by what you actually mean — "japan", "oled", "rain" and "games" all find the right themes. Star the ones you keep coming back to. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ SET THE PACE ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Every animated theme has a speed dial, from 10% to 100%. Turn a busy one down until it barely drifts, or leave it running at full. The slowdown happens inside the animation rather than by dropping frames, so a theme at 15% still draws every frame — no judder, no ghosting. And 100% means the pace that theme should run at, not whatever it happened to be written at: every theme was measured, and the 26 busiest were reined in so the dial means the same thing wherever you are. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ OR BRING YOUR OWN ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Set any picture as your background and Vellum reads a palette out of it, so the sidebar, composer and text settle around your image instead of fighting it. Tune the drift and the opacity to taste. It is stored on your own machine and never uploaded. (Pro) ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ WHY VELLUM ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ✓ Genuinely animated — not static gradients ✓ Simulated, not looped — the metronome's tempo follows the weight on its rod, a comet's tails stream away from the sun, fireflies fall into sync by nudging each other ✓ Hand-written canvas, not video — sharp at any window size, a fraction of the memory ✓ Works on both ChatGPT and Claude ✓ 10 free dark modes, forever, no account needed ✓ Search and favourites, so 250 stays browsable ✓ Syncs across your devices ✓ One-click screenshots of your themed chat ✓ Dark-mode native — tuned so text stays comfortable to read for hours ✓ No data collected. No tracking, no analytics, no accounts. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ONE THING FIRST ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Vellum is built for dark mode. Switch appearance to Dark in ChatGPT or Claude's own settings before you pick a theme — in light mode they look washed out. Vellum will say so if it notices you are still in light. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ FREE vs PRO ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 10 refined dark modes are free forever — no card, no sign-up. Graphite, Carbon, Oat, Mocha, Sage, Pine, Fog, Plum, Ember and the plain Default: one for every mood of dark, all tuned for reading against for hours. Pro unlocks all 250 — every animated background, the speed dial, your own image as a background, and new themes as they drop. Try the whole collection free for 7 days. Cancel any time. For teams, a company code applies your own colours and logo across everyone's install. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ PRIVACY ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Vellum collects nothing. No browsing history, no chat contents, no analytics, no account. It does not read what you type — it draws a background behind it. Your themes are stored in your own browser and sync via your Google account. Vellum keeps a local flag in your browser recording when your trial began, so that reinstalling does not hand out a second one; it is never transmitted. An image you set as your background stays on that device. The extension loads nothing from anyone else's server — no fonts, no CDNs, no scripts. The only network requests it ever makes are to validate a Pro licence key, and to fetch your company's theme if you enter a company code. Three permissions, all of them used: storage (remember your theme), activeTab (the screenshot button), alarms (re-check a licence every 12 hours). Vellum is an independent extension and is not affiliated with, endorsed by, or sponsored by OpenAI or Anthropic.