Write Lint

Product Introduction

1. Definition: Write Lint is a native macOS menu-bar application (a system utility) that functions as a real-time, AI-powered proofreading and text refinement tool. It leverages on-device large language models (LLMs) within the Apple Intelligence framework.
2. Core Value Proposition: It exists to provide immediate, private, and frictionless text polishing—correcting typos, punctuation, and grammar—directly from any application on a Mac. Its primary value is privacy-first AI proofreading and offline grammar checking via Apple's on-device Foundation Models.

Main Features

1. Global System-Wide Shortcut (⌘⇧L): The app runs as a floating window accessible from any macOS application. Pressing the keyboard shortcut Command-Shift-L instantly summons the polishing interface. This enables system-wide text editing without switching contexts or copying text into a separate web app.
2. On-Device AI Processing by Default: The core functionality uses Apple Intelligence and its on-device Foundation Models. This means all text analysis for grammar, spelling, and style happens locally on the user's Mac (M-series or later with macOS 26.0+). This ensures zero latency proofreading and fully offline AI editing, with no data sent to external servers.
3. Bring-Your-Own-Key (BYOK) Cloud Model Support: For users preferring different AI capabilities, Write Lint offers optional integration with third-party LLMs. Users can provide their own Claude API key or OpenAI API key. The app acts as a secure client; the key and text are sent directly to the chosen provider (Anthropic or OpenAI), bypassing Write Lint's servers entirely, enabling private cloud AI proofreading.
4. Inline Diff Review Workflow: After processing, the app presents a clear side-by-side or diff view showing the original text versus the AI-suggested changes. The user can then accept all changes, reject them, or copy the polished version. The window is dismissed with the Escape key, streamlining the review and accept editing workflow.

Problems Solved

1. Pain Point: The disruption of workflow when switching to a separate browser tab or application for grammar and spell check. It solves the problem of context-switching fatigue during writing tasks.
2. Target Audience: Mac power users (writers, developers, students, professionals) who value privacy, speed, and system integration. Specifically, technical writers, bloggers, email-heavy professionals, and anyone writing in environments without internet access (e.g., on airplanes).
3. Use Cases: Polishing emails in Mail, refining documentation in VS Code or Xcode, improving chat messages in Slack or Discord, cleaning up text in Notes or TextEdit, and finalizing content in web-based CMS editors—all without leaving the current app.

Unique Advantages

1. Differentiation: Unlike cloud-based grammar checkers (Grammarly, ProWritingAid, Hemingway Editor online), Write Lint's default mode requires no account, subscription, or internet connection and leaks zero data. Unlike basic macOS system spellcheck, it uses advanced LLMs for contextual grammar and rewriting.
2. Key Innovation: Its architecture as a lightweight macOS menu-bar client for Apple's native on-device AI models. It productizes a system-level capability (Apple Intelligence) into a dedicated, utility-focused interface. The optional BYOK model is also unique, allowing users to leverage premium cloud models without the developer acting as a middleman or charging markup.

Frequently Asked Questions (FAQ)

1. How does Write Lint ensure my writing privacy? By default, Write Lint uses Apple's on-device Foundation Models, meaning your text is processed entirely on your Mac and never leaves your device. If you use a cloud key, your text is sent directly to your chosen provider (Anthropic/OpenAI); Write Lint's servers never intercept or store it.
2. What are the system requirements for Write Lint? Write Lint requires macOS 26.0 or later on a Mac with Apple Silicon (M-series chip) and Apple Intelligence enabled. This is necessary to access the local on-device AI models that power its default proofreading mode.
3. Is Write Lint really free? Yes, the core application is free. It monetizes neither the on-device Apple model nor the optional cloud model integrations. If you use Claude or OpenAI, you pay those providers directly based on their own usage pricing; Write Lint adds no fees.
4. Can I use Write Lint with Google Docs or Microsoft Word? Yes. Because it uses a global macOS keyboard shortcut, it works with any application that allows text selection, including web browsers running Google Docs and native apps like Microsoft Word for Mac.
5. What's the difference between the on-device model and using my Claude key? The on-device Apple model offers maximum privacy and speed but may have different stylistic strengths and capabilities compared to Claude or GPT-4. Using your own Claude/OpenAI key provides access to the specific features and writing style of those advanced cloud models, at the cost of an internet connection and API usage fees.