Know when your AI is about to forget.
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Headroom is a browser extension that gives you a real-time, visual gauge of your context window usage in AI chat conversations — so you know before the AI starts forgetting.
- Zero setup — No account, no API key, no configuration. Install and it just works.
- Real-time gauge — Watch your context window fill up as you chat. 🟢 Green (plenty of room) · 🟠 Yellow (filling up) · 🔴 Red (time for a new conversation).
- Per-round breakdown — See estimated token counts for every Q&A pair, input and output separately.
- Privacy by design — Conversation text is read transiently to count tokens, then discarded. Only the token counts are stored, locally and optionally in your own cloud storage. No Headroom server exists.
Supported Platforms & Default Context: DeepSeek (1M), ChatGPT (128K), Gemini (1M), Kimi (256K), Qwen (1M), 通义千问 (1M), 豆包/Doubao (256K).
Context limits are auto-detected per platform and user-overridable. All seven platforms' request parsing and DOM selectors were captured live (2026-06). Built with a platform-agnostic adapter architecture — adding a new AI chat platform is a matter of writing one adapter.
When you're deep in a long conversation with an AI, you've probably experienced this: constraints you set 10 rounds ago get forgotten, earlier decisions get contradicted, and output quality degrades silently. Context windows have limits — when they fill up, the AI quietly drops earlier information. None of the major AI chat platforms show you how much room you have left.
Who is this for? Professionals who use AI chat as part of their daily workflow — developers, researchers, writers, analysts. If your conversations regularly exceed 20+ rounds for architecture discussions, code reviews, research deep-dives, or technical writing, Headroom helps you maintain conversation quality.
Not a token cost calculator. AI models are getting cheaper by the month — the concern is context quality: making sure your AI hasn't silently forgotten something critical.
Install from the store badges at the top ↑ — each badge links directly to that browser's extension store.
Headroom is Manifest V3 only (MV2 is not supported) and requires a recent browser version: Google Chrome ≥ 149, Microsoft Edge ≥ 149, Firefox ≥ 151.
Known Platform Differences
| Behavior | Chrome | Edge | Firefox |
|---|---|---|---|
| Icon grays on non-AI pages | ✅ | ✅ | ✅ |
| Panel auto-closes when leaving AI page | ✅ | ✅ | ❌ (content switches to hint page) |
| Panel auto-restores when returning to AI page | ✅ | ❌ (manual click needed) | ✅ (content restores) |
Edge limitation: sidePanel.setOptions({ enabled: true }) does not auto-restore the panel after switching back to an AI platform tab. Microsoft confirmed this is "by design" (issue #222, open since Nov 2024, no fix). Workaround: click the toolbar icon to reopen.
Firefox limitation: sidebarAction.close() requires a user gesture and cannot be called on tab switch (Firefox platform limit). The sidebar must be manually closed by the user. When switching to a non-AI page, the sidebar content switches to a hint page via sidebarAction.setPanel().
Headroom is fully functional with zero cloud setup. For most users, most of the time, that's everything.
Optionally, you can connect your own Upstash Redis KV — create a free account, provision a KV instance, and paste the REST credentials into the extension settings (BYOK: the data lives in your own private storage, and the credentials never leave your browser). What connecting adds:
- Settings sync across devices — thresholds, language, per-platform context limits, and token-coefficient overrides follow you.
- Count continuity — when a platform's history API can't return the full history (pagination caps, interrupted fetches), the cloud record preserves previously counted rounds so your cumulative total never silently shrinks.
Upstash's free tier (pricing) includes 256 MB storage and 500,000 commands/month — far beyond what a single user generates. Headroom stores only token counts per round (no conversation text), so storage is a non-issue (~4 KB per 50-round conversation).
- WXT — Next-gen web extension framework (Manifest V3)
- Native Side Panel API — Browser-native sidebar (Chrome
sidePanel, FirefoxsidebarAction) - Heuristic token estimation — 6-way per-script coefficient engine (CJK, Kana, Hangul, Cyrillic, Arabic, Latin); character-based for CJK/kana/Hangul, word-based for the rest. No heavy tokenizer bundled (keeps the extension light and model-agnostic)
- Upstash Redis KV — Optional user-owned cloud storage (BYOK model)
We welcome bug reports, feature requests, and code contributions!
- Found a bug? → Report an issue
- Want to contribute? → Read our Contributing Guide
- Testing help needed? → See open issues labeled
needs-test
Development
npm install
npm run dev # Dev mode with HMR (Chrome default)
npm run dev:firefox # Dev mode for Firefox
npm run build # Production buildSee AGENTS.md for full development guidelines and architecture details.
Headroom reads your conversation text only to count tokens — it stores only the counts, never the text itself, locally and in your own Upstash KV (if configured). There is no Headroom-operated server and no third-party tracking. Full details: PRIVACY.md.
Copyright 2026 ZM-BAD.
Licensed under the Apache License, Version 2.0 — see 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.