Hone is a professional-grade browser extension that brings modern LLM capabilities directly into any text box, editor, or textarea on the web.
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Polish grammar, flow, and vocabulary in-place. |
Rewrite naturally while keeping the original meaning intact. |
Catch typos, grammar slips, and awkward phrasing instantly. |
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Shift tone to business-appropriate with confidence. |
Make text conversational and easy to read. |
Add energy, enthusiasm, and engagement. |
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Warm, polite, and approachable phrasing. |
Condense rambling text into crisp, direct sentences. |
Expand brief notes into detailed, thorough prose. |
+ 🛠️ Custom Actions — the real power of Hone. Build your own AI tools tailored to your workflow. Assign them icons, colors, even per-action models. This is what makes an open-source tool truly open-source — you're not stuck with what we built, you build what you need.
Hone works wherever you type on the web. Here's what it does in plain language:
- 📝 Polishing a work email
- You draft a reply in Gmail, hit Alt+Shift+D, pick Improve writing, and Hone rewrites it to sound clear and professional — right inside the compose box.
- ✍️ Replying on social media
- Writing a tweet or a Reddit comment that doesn't quite land? Select the text and ask Hone to make it Casual or Friendly so it reads naturally.
- 📄 Filling in a job application
- You've typed a short answer in a textarea. Hone can Lengthen it to add detail, or shift to Professional tone before you submit.
- 🐛 Fixing a bug report
- You wrote a rough description in GitHub Issues. Use Fix spelling & grammar to clean it up, then Paraphrase so it's clearer for the team.
- 💬 Chatting on Discord or WhatsApp Web
- Hone integrates deeply with Slate.js (Discord) and Lexical (WhatsApp Web) — run actions directly inside rich-text editors without breaking formatting.
- 🗂️ Drafting a Notion doc or Google Doc
- Write freely first, then refine sentence by sentence using any Hone action — no context switching to another tab or tool.
- 🎨 Creating custom writing tools
- Actions Studio lets you build your own AI-powered text tools. For example: create a "Summarize" action with the prompt
Summarize the following text into 3 bullet points: {{input}}, assign it a FileText icon in purple, and bind it to Alt+Shift+S. It appears in your menu just like a built-in action — except you designed it for exactly what you need. - 🔍 Reviewing before committing
- Enable Preview before replacing on any action to see a before/after panel before applying changes to your text.
Hone is provider-agnostic. Bring your own API key — or use the preconfigured free tier.
| Provider | How to use | Pricing |
|---|---|---|
| OpenRouter Free | Get a free API key at openrouter.ai. Hone auto-cycles through 5 free models (Gemma 4 26B, Nemotron 3 30B, Llama 3.2 3B, etc.) with up to 3 retry passes. | Free-of-cost with rate-limit fallback |
| OpenRouter Paid | Use any model slug from OpenRouter's catalog (GPT-4o, Claude, etc.). | Pay-as-you-go via OpenRouter credits |
| OpenAI | Bring your own sk-proj-... key. Supports custom endpoints (proxies, local gateways). |
Your OpenAI plan |
| Anthropic Claude | Paste your sk-ant-... key from the Anthropic Console. |
Your Anthropic plan |
| Google Gemini | Use a free API key from aistudio.google.com. Generous free tier. | Free tier available |
| Google AI Studio | Gemma models via @google/genai SDK with thinking config. Also uses aistudio keys. |
Free tier available |
No API key? Start with OpenRouter Free — sign up at openrouter.ai, grab a key, paste it in Hone's settings, and you're good to go. Zero cost.
graph TD
User([User]) -->|Focuses text field| Trigger[✨ Hone Trigger Dot]
Trigger -->|Click / Alt+Shift+D| Menu[Floating Action Menu]
Menu -->|Select action| Engine[AI Provider Engine]
Engine -->|Returns result| Preview[Before/After Preview Panel]
Preview -->|Accept| Replace[Text Replaced In-Place]
Preview -->|Discard| User
style User fill:none,stroke:#666,stroke-width:2
style Trigger fill:#1e1e2e,stroke:#cba6f7,stroke-width:2
style Menu fill:#1e1e2e,stroke:#cba6f7,stroke-width:2
style Engine fill:#1e1e2e,stroke:#89b4fa,stroke-width:2
style Preview fill:#1e1e2e,stroke:#a6e3a1,stroke-width:2
style Replace fill:#1e1e2e,stroke:#f9e2af,stroke-width:2
| Action | What it does |
|---|---|
| Improve writing | Enhances grammar, flow, vocabulary — makes any text polished and engaging |
| Paraphrase | Rewrites while preserving meaning — fresh wording, natural flow |
| Fix spelling & grammar | Corrects errors without changing tone or structure — powered by Harper.js for instant local checking |
| Professional tone | Shifts text to clear, business-appropriate language |
| Casual tone | Makes text conversational and easy to read |
| Exciting tone | Adds enthusiasm and energy |
| Friendly tone | Warms up the phrasing |
| Shorter | Condenses text to be direct and concise |
| Longer | Expands text with relevant detail and descriptive depth |
| Custom actions | User-defined prompts with custom icon, color, provider, model, and temperature |
Hone isn't limited to what we built. The Actions Studio is the heart of the project — it lets anyone create custom AI-powered text tools without writing code. You define the prompt, pick an icon and color, and it sits in your menu alongside the built-in actions. That's the point: an open-source tool that you shape to fit your workflow, not the other way around.
Example — a "Summarize" tool:
- Click Create New Action in Actions Studio
- Name it
Summarize - Set the prompt template to:
Summarize this into 3 concise bullet points:\n\n{{input}} - Pick the
FileTexticon, set color to purple - Optionally assign it to a specific provider/model
- Save — it's now in your action menu on any website
Everything you can configure:
- Prompt templates with
{{input}}variable — the selected text gets injected at rewrite time - System prompts — set context/role instructions for the AI
- Icon picker — choose from 100+ Lucide icons to identify your action
- Accent color — pick from 8 preset colors for visual distinction
- Per-action provider — override the global provider for a specific action
- Per-action model — target a specific model for this action only
- Temperature slider — control creativity (0.0 = deterministic, 2.0 = max creativity)
- Preview mode — toggle before/after review panel instead of inline replacement
- Enable/disable — turn actions on/off without deleting them
- Test playground — run your action against sample text directly in the options page
When no text is selected, Hone intelligently guesses what you want to rewrite:
- Selection — explicitly highlighted text
- Sentence — auto-detected via regex
- Paragraph — blank-line delimited block
- Full field — entire editor contents
Cycle through options in the action menu with a single click.
Hone integrates Harper.js — a well-known, open-source grammar checker that runs entirely in your browser via WebAssembly. This provides instant spelling and grammar corrections without sending your text to any external server.
Why Harper.js?
- Privacy-First: All grammar checking happens locally in your browser. Your text never leaves your device for spelling/grammar analysis.
- Instant Response: WebAssembly execution delivers sub-100ms correction times for typical text segments — no network latency.
- No API Costs: Unlike cloud-based grammar services, Harper.js is free to use with no rate limits or subscription fees.
- Offline Capable: Works without an internet connection once the WASM module is loaded.
- SEO-Friendly: Harper is a widely recognized name in the developer community, making Hone more discoverable for users searching for grammar checking solutions.
How it works:
- When you select "Fix spelling & grammar," Hone first checks if the text is primarily English using Chrome's language detection API.
- Harper.js runs locally as a WebAssembly module, analyzing your text for spelling errors, grammar mistakes, and awkward phrasing.
- Corrections are displayed in the preview card with word-level diff visualization showing exactly what changed.
- Smart fallback skips correction if too many errors are detected (indicating non-English text or gibberish).
Performance:
- WASM-based execution for near-native speed
- Language detection prevents unnecessary processing on non-English text
- Smart error threshold avoids false positives on code snippets or technical content
| Editor | Integration method |
|---|---|
| Slate.js (Discord) | React Fiber traversal, direct editor.insertText() call |
| Lexical (Facebook, WhatsApp Web) | beforeinput event with insertReplacementText |
| ProseMirror | Contenteditable-based DOM manipulation |
| Twitter/X | Custom editor adapter |
| Native inputs | <input>, <textarea> — via execCommand and value tracker |
| Generic contenteditable | Fallback DOM range manipulation |
- Menu toggle — configurable combo (default:
Alt+Shift+D) to open/close the floating action menu - Quick action — configurable combo to run a specific action instantly without opening the menu
- System commands — manifest-level shortcuts that work even when websites intercept keystrokes
- Shortcut recorder — press any key combination to capture it in settings
The Options page gives you full control:
- Dashboard — at-a-glance status: API connection, active shortcuts, total rewrites, recent activity
- API Providers — manage keys, models, and endpoints for all 6 providers
- Key Bindings — record custom shortcuts, hide the floating dot (keyboard-only mode)
- Rewrite History — searchable, virtual-scrolled log with before/after detail view, copy, and delete
- Actions Studio — create, edit, and test custom actions
- Modern shadcn/ui components — built on Radix primitives for accessible, composable UI patterns
- Material Web Components — Google's Material Design 3 web components for dialogs, menus, switches, and buttons
- Shadow DOM isolation — page CSS can't leak into Hone's interface
- Floating UI — menu and preview panels follow the text caret automatically (flip, shift, collision detection)
- Glassmorphic MD3 design — Material Design 3 tokens with frosted-glass surfaces
- Spring physics —
cubic-bezier(0.175, 0.885, 0.32, 1.275)for natural, bouncy micro-interactions - Web Audio API haptics — buttons and switches produce tactile audio feedback
- Trigger dot — purple sparkle icon that appears when you focus any text field (toggleable)
Extension Popup Active engine, shortcuts & quick settings |
Options Dashboard Status overview, metrics & recent activity |
In Action Floating menu over a web text field |
Actions Studio Build your own writing tools |
git clone https://github.com/rabden/hone-extension.git
cd hone
npm installnpm run buildOutputs to dist/.
- Open
chrome://extensions/ - Enable Developer mode (top-right)
- Click Load unpacked (top-left)
- Select the
dist/directory
- Click the Hone icon in the toolbar, then Open settings
- Go to API Providers, pick your provider, paste your key
- Or grab a free key from openrouter.ai and select OpenRouter Free
Focus any text input on any webpage. Press Alt+Shift+D (default) or click the purple sparkle dot. Pick an action — your text transforms in-place.
| Component | What it does |
|---|---|
| Content Script | Injected into every page. Renders the menu/preview UI in a Shadow DOM. Detects editor frameworks (Slate, Lexical, etc.) and adapts accordingly. |
| Background Worker | Routes AI requests to the configured provider. Handles OpenRouter Free model fallback cycling. Saves rewrite history. |
| Main World Bridge | Runs in the page's main JavaScript context. Traverses React Fiber trees to invoke editor event handlers that are inaccessible from the isolated world. |
| Floating UI | @floating-ui/dom for auto-positioning relative to the text caret (flip, shift, collision detection). |
| Transaction Engine | Low-level framework-specific commit logic — React Fiber walking, beforeinput events, execCommand — to inject rewritten text without breaking the host editor's state. |
Note
For a deep dive into React Fiber traversal, editor adapter architecture, and file-by-file breakdown, see architecture.md.
This project is licensed under the MIT License. See LICENSE for details.