A free, open-source Grammarly alternative for your browser and Microsoft Word — powered by your own Gemini API key.
▶ 2-minute tutorial on YouTube — install GemType, add your free Gemini key, and see grammar checking + rewrites in action.
GemType runs everywhere you write — all surfaces share the same private, bring-your-own-key core (your text goes straight to Google's Gemini API, never through a server of ours):
| Platform | Status |
|---|---|
| Chrome | Live on the Chrome Web Store |
| Edge | Live on Edge Add-ons |
| Firefox | Submitted to AMO — see extension/manifest.firefox.json |
| Microsoft Word | Office task-pane add-in — see msword/ |
| Safari | Build ready (needs the Apple Developer fee — sponsor) |
| iOS / Android keyboards | Planned |
Works in any language (auto-detected), on any website, and now inside Word.
- Live grammar and spelling checking — underlines appear in any text field about a second after you stop typing: Gmail, LinkedIn, X, Reddit, GitHub, anywhere
- One-click fixes — click an underline and accept the correction;
Ctrl/Cmd+Zalways undoes - Sentence verification — after every accepted fix, the surrounding sentence is automatically re-checked, so word-level fixes never leave broken sentences behind
- Rewrite on demand — select text for a floating toolbar with Improve, Fix, Shorten, Formal, and Casual actions, also available from the right-click menu
- Context-aware suggestions — an LLM judges whole sentences in any language, not just pattern rules
- Bring your own key — uses your free Google AI Studio key; no account, no subscription, no middleman server
- Private by design — text goes only to Google's Gemini API; no tracking, no analytics, nothing else phones home
- Full control — per-site disable, global toggle, model picker, language setting; honors
data-gramm="false"opt-outs
| GemType | Grammarly | |
|---|---|---|
| Price | Free — bring your own Gemini key (free tier, no card required) | Free plan is limited; Premium $12–30 per month |
| Grammar and spelling fixes | Unlimited | Full corrections require Premium |
| Sentence re-check after each accepted fix | Automatic | Not available |
| AI rewrites (Improve, Shorten) | Included | Premium |
| Preset styles (Formal, Casual) | Included | Premium |
| Languages | Any language Gemini understands, auto-detected | English and a small set of variants |
| Trackers and analytics | None | Product analytics and telemetry |
| Account required | No | Yes |
| Where your text is processed | Google's Gemini API only, with your key — no middleman server | Grammarly's servers |
| Open source | Yes (Apache 2.0) | No |
| Google Docs | Not supported (Google whitelists specific vendors) | Supported |
What does "bring your own key" really cost? For a single person typing, the free Gemini tier is more than enough — GemType checks only after you pause, skips unchanged text, and caches results, so even a heavy writing day stays comfortably inside the free quota. On the paid tier, a typical check costs around $0.0003 — roughly one dollar per month for very heavy daily use, compared with $144–360 per year for Premium.
 |
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| Live checking — underlines and issue-count badge | Click an underline, accept the fix |
 |
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| Review all suggestions from the badge | Select text to rewrite: Improve, Fix, Shorten, Formal, Casual |
Install from the Chrome Web Store or from Edge Add-ons — one click, then add your free Gemini API key from Google AI Studio.
Or install manually (developer mode)
Manual (developer mode):
- Download or clone this repository
- Open
chrome://extensionsand enable Developer mode - Click Load unpacked and select the
extension/folder - Get a free API key at aistudio.google.com/apikey (no credit card required)
- Open GemType Settings from the toolbar icon, paste the key, and click Save & test
Firefox — the same code base with extension/manifest.firefox.json (event-page background + browser.* compatibility). AMO listing in review; build steps under Development.
Microsoft Word — a task-pane add-in that checks your document and rewrites selected text right inside Word (Windows, Mac, and the web). See msword/ and its README to run or install it.
Safari — the same code base wraps into a Safari App Extension; see Safari build below.
page (any website)
┌──────────────────────────────────────────┐
│ content script │
│ ├─ detects textarea / contenteditable │
│ ├─ draws underline overlay (shadow DOM, │
│ │ never touches the page's editor) │
│ └─ applies fixes via execCommand │
│ (native undo + framework-safe) │
└──────────────┬───────────────────────────┘
│ chrome.runtime messaging
┌──────────────▼───────────────────────────┐
│ background service worker │
│ ├─ queue + cache + 429 backoff │
│ └─ Gemini generateContent │
│ (structured JSON output) │
└──────────────┬───────────────────────────┘
▼
generativelanguage.googleapis.com
(your API key, your data)
- Overlay, not injection — underline positions come from
Range.getClientRects()(rich editors) or a mirror element (plain fields); the page's DOM is never modified, so React, Vue, and ProseMirror editors stay stable - Snippet anchoring — the model returns exact text snippets, located client-side and re-anchored live as you type (LLM character offsets are unreliable)
- Token-frugal — debounced checks, unchanged-text skipping, response caching, and sentence-scoped re-checks keep free-tier quota comfortable for daily use
| Editor type | Status |
|---|---|
Plain textarea / input (GitHub, forums, most forms) |
Supported |
contenteditable rich editors (Gmail, LinkedIn, X) |
Supported |
| Shadow-DOM web components (Reddit) | Supported |
| Google Docs (canvas rendering; requires a Google-whitelisted extension ID) | Not supported — use the right-click rewrite instead |
- The text you are editing is sent only to
generativelanguage.googleapis.com(Google's Gemini API) using your own key — see PRIVACY.md - Your API key lives in
chrome.storage.localon your device; it is never synced or transmitted anywhere else - Password fields are never read, and payment or one-time-code fields are skipped at the code level
- No accounts, no telemetry, no third-party servers
- Sites can opt out with
data-gemtype="false"; Grammarly-style opt-outs are honored as well
extension/ the browser extension (MV3, no build step) — Chrome, Edge, Firefox
├── manifest.json Chrome / Edge manifest
├── manifest.firefox.json Firefox (AMO) manifest — event-page background + gecko id
└── src/
├── background.js Gemini API calls, cache, rate limiting
├── content/
│ ├── content.js field discovery + checking loop
│ ├── overlay.js underlines, badge, suggestion card
│ ├── refine.js selection rewrite toolbar
│ └── util.js text extraction, offset maps, safe replacement
├── options.html/js API key, model, language, disabled sites
└── popup.html/js global + per-site toggles
msword/ the Microsoft Word add-in (Office.js task pane)
├── manifest.xml Office add-in manifest
└── src/taskpane/ task pane UI + Office.js integration + Gemini calls
safari/ Xcode wrapper project (generated)
assets/ logo, hero animation, screenshots
test/
├── test-page.html manual test fields (incl. scroll + opt-out cases)
└── harness.html automated harness with a mocked Gemini backend
# run the mock harness (no API key needed)
python3 -m http.server 8377
open http://localhost:8377/test/harness.htmlFirefox — load extension/ with manifest.firefox.json via about:debugging → Load Temporary Add-on. The code auto-aliases Firefox's promise-based browser.* to chrome.*, so one codebase runs in both.
Microsoft Word add-in — see msword/README.md: npm install && npm run certs && npm start, then sideload msword/manifest.xml into Word.
Safari build (requires Xcode):
xcrun safari-web-extension-converter extension --project-location safari --app-name GemType --macos-only
xcodebuild -project safari/GemType/GemType.xcodeproj -scheme GemType -configuration Debug buildThen in Safari: Settings → Developer → Allow unsigned extensions → enable GemType.
- Chrome Web Store — live
- Edge Add-ons — live
- Firefox (AMO) — submitted
- Microsoft Word add-in — working; AppSource submission in progress
- Safari App Store (build ready; needs Apple Developer membership — sponsor)
- iOS / Android keyboards sharing the same backend
- Hosted-key option (proxy backend) — zero setup for end users
- Tone and style preferences per site
GemType sends the text you are actively editing to Google's Gemini API for analysis. Do not use it in fields containing passwords, secrets, or text you are not comfortable processing with a cloud AI service — or disable it for those sites with one click.
Is GemType a free alternative to Grammarly? Yes. GemType provides live grammar checking, one-click fixes, and AI rewrites on any website at no cost — you supply your own free Gemini API key from Google AI Studio. There is no subscription and no premium tier.
Is the Gemini API key really free? Do I need a credit card? Google AI Studio issues free API keys with no credit card required. The free quota is far more than one person needs for everyday typing; GemType is built to stay inside it (debounced checks, caching, sentence-scoped re-checks).
Is GemType safe? Where does my text go? The text you edit is sent directly from your browser to Google's Gemini API, authenticated with your own key. There is no GemType server, no account, and no analytics — the developers never see your text. Password, payment, and one-time-code fields are never read. See PRIVACY.md.
Which websites does it work on? Any site with a normal text field or rich editor: Gmail, LinkedIn, X (Twitter), Reddit, GitHub, forums, web mail, CMS editors. Google Docs is the one notable exception, because it renders documents to a canvas and restricts its annotation API to Google-whitelisted vendors.
Does it work in languages other than English? Yes. GemType auto-detects the language you are writing in and checks it with the same model — Spanish, French, German, Portuguese, Bengali, Hindi, Arabic, Chinese, Japanese, and anything else Gemini understands. You can also pin a language in settings.
How is this different from pasting my text into ChatGPT or Gemini? GemType works where you type: mistakes are underlined in place while you write, fixes apply with one click and native undo, and each fix triggers an automatic re-check of the sentence. No copy-paste round trips.
Does it slow down my browser? No. The content script stays inert until you focus a text field, checks only after you pause typing, and draws its UI on a lightweight overlay without touching the page's own editor.
Can it run fully offline or with a local model? Not yet. A pluggable backend (including self-hosted models) is on the roadmap.
Contributions are welcome — this project went from an empty folder to a working extension in a day, and there is plenty of interesting work left:
- Compatibility fixes for stubborn editors (report a site, ideally with a
reduced test case in
test/test-page.html) - Translations for the UI
- The Word add-in's native annotation API (inline squiggly underlines in Word)
- The proxy backend for a zero-setup hosted mode
- Help with the iOS / Android keyboards
Open an issue to discuss anything bigger before you build it. If GemType helped you, starring the repository genuinely helps others find it.
GemType is free, open source, and unfunded. The Safari version is built and working — but shipping it to the App Store requires the Apple Developer Program fee of $99/year, which is currently the only thing standing between this project and Safari users (and, later, the iOS keyboard).
If you or your company find GemType useful, consider sponsoring: github.com/sponsors/riponcm — the first goal is exactly one thing: the Apple Developer fee. Every sponsor is credited in this README.
Apache License 2.0 © 2026 Ripon Chandra Malo (Matily). See NOTICE.
The GemType name and logo are trademarks and are not covered by the Apache license — see TRADEMARK.md. Please give forks their own name and icon.
Another open source product from Matily — open source software studio.