Grammarly alternatives that actually run on-device

September 14, 2026·4 min read

An open laptop showing gray placeholder bars sits on a wooden desk beside a red pencil and a compact charcoal desktop computer.

The defensible alternatives to Grammarly that run on-device are Harper for English, Antidote 12 for English or French, a self-hosted LanguageTool server for multiple languages, Grammalecte for French and Vale for technical style rules. Typeahead is another local option for writers who want sentences completed as they type.

What on-device really means

On-device means your writing is processed on the same computer where you typed it. A desktop icon proves only that an app is installed. The checker behind it may still send text to a remote service.

Local software can use the internet for activation, updates or model downloads without uploading your writing. That distinction matters more than the shape of the app, as this closer look at what happens when an AI tool reads your typing explains.

The short comparison

Choose Harper for free local English spelling and grammar checks.
Choose a local LanguageTool server for multilingual proofreading and client flexibility.
Choose Antidote 12 for an installed English or French reference suite.
Choose Grammalecte for free French grammar and typography checking.
Choose Vale to enforce a technical publication’s own style rules.
Choose Typeahead for local sentence completion while you are writing.

Harper for local English checks

Harper performs every check locally using a deterministic engine rather than an LLM. It requires no account or GPU and its official documentation says it does not collect usage data.

Harper covers American, British, Canadian, Australian and Indian English. Integrations include Chrome, Edge and Firefox as well as VS Code, Neovim, Obsidian, WordPress and other editors. Its system-wide desktop beta currently requires macOS 14 or later and supports Apple Silicon and Intel Macs.

Harper is the clearest free answer for someone who writes in English and wants ordinary spelling and grammar checks without sending prose to a service.

LanguageTool on localhost

LanguageTool becomes genuinely on-device when you run its standalone server on your computer and direct its clients to localhost. The ordinary desktop download alone does not establish that arrangement.

LanguageTool calls local server installation an advanced setup. Its browser extension can connect to that server, though the local edition excludes AI-based rules that remain cloud-only. The open-source core supports English, Spanish, French, German, Portuguese, Polish, Dutch and more than 20 additional languages.

Antidote 12 for English and French

Antidote 12 installs locally on Windows and macOS. Its corrector, dictionaries and language guides remain available without an internet connection.

Installation, activation, connected features and periodic subscription validation require networking. Ordinary correction stays local, while Reformulation mode sends the selected passage to Antidote’s servers. The company’s privacy policy explains that processing boundary.

Grammalecte for French

Grammalecte is a free, open-source French grammar and typography checker. It integrates with LibreOffice, OpenOffice, Thunderbird, Firefox and Chromium-based browsers.

Its Firefox implementation needs no server, works offline and sends no information online. It also includes French spelling dictionaries, conjugation tools, typography formatting and a personal dictionary editor.

Vale for documentation rules

Vale runs offline on Windows, macOS and Linux. It is a command-line prose linter built around customizable spelling and style rules rather than broad conversational grammar correction.

That makes Vale a strong fit for documentation teams that need enforceable terminology, capitalization and house style across a repository. Its value is consistency that can become part of an existing writing and review process.

Typeahead for completion while typing

Typeahead brings local AI to the moment before a sentence is finished. It completes sentences the writer has already started, in the writer’s voice. That makes it a distinct workflow beside tools that inspect a draft afterward, a distinction covered in AI autocomplete is not AI writing.

Typeahead processes writing locally. Network activity is limited to license activation, optional update checks and the one-time download of your AI model. Writing never leaves the Mac. It costs $79 one-time and requires macOS 14 or later.

The detail I appreciate every day is accepting one suggested word with the right arrow, then writing the rest myself. The cursor keeps moving and the sentence remains mine.

Choose by the writing job

Start with language and workflow. Harper covers local English correction. Grammalecte specializes in French. Antidote supplies a deeper installed reference suite, LanguageTool rewards people comfortable running a local server and Vale gives technical teams rules they can define.

For help during composition, Typeahead works at the cursor. Together, these tools show why “on-device Grammarly alternative” describes several different jobs. The right answer depends on whether you want correction, multilingual checking, style enforcement or sentence completion.