Self-host Grammarly

Writing assistant / grammar + style checker · Category: wiki, docs & notes

Grammarly checks grammar, style, tone, and (in paid tiers) plagiarism + AI rewriting, integrating into browsers, Word, and IDEs. The self-hostable replacements cover the grammar/style core well; the LLM-powered tone and rewrite features are where they're thinner.

Grammarly pricing anchor: Free for basics; $12-15/user/mo for Premium; Business adds team analytics.

LanguageTool languagetool-org/languagetool alive

GitHub: ★ 14.5k · last commit today · 2110 open issues
License: LGPL-2.1
Server is LGPL-2.1; the premium 'Picky' rules and the n-gram corpora are paid add-ons even on self-host.
Setup time: 10min — single Java process, optional docker-compose
Monthly cost: $5-10 VPS; the larger n-gram dataset wants ~16GB disk + a few GB RAM if you enable it.

Migration sketch. Run `docker run -p 8010:8010 erikvl87/languagetool`. Browser extension (LanguageTool's official one) lets you point at your server URL — replaces the Grammarly extension. For Word / Google Docs, LanguageTool ships add-ons that also accept a custom server URL. IDE: the LanguageTool LSP server works inside VSCode / IntelliJ via community plugins.

Good fit forAnyone whose Grammarly use is mostly grammar + style + multilingual checking — LanguageTool covers 30+ languages.

Weak atTone, rewrite, and the AI 'make it sound more confident' features are not in the free OSS server.

Harper Automattic/harper alive

GitHub: ★ 10.5k · last commit 1d ago · 506 open issues
License: Apache-2.0
Setup time: 5min — Rust binary, also runs as a VSCode extension and a browser extension
Monthly cost: $0 — Harper runs locally (LSP) or in-browser (WASM) by default; no server required for personal use.

Migration sketch. Install the Harper VSCode / Obsidian / Zed plugin or the browser extension. There is no migration data in Grammarly to bring over — switch the extension and point your IDE at the Harper LSP. For self-hosted as a server, run `harper-ls --stdio` behind any LSP-aware proxy or run the WASM bundle in your own page.

Good fit forDevs who want grammar/style checking that runs fully on-device with low latency and zero data leaving the box.

Weak atYounger project — fewer rules than LanguageTool; English-only at the moment.

Vale errata-ai/vale alive

GitHub: ★ 5.37k · last commit 8d ago · 102 open issues
License: MIT
Setup time: 10min — single Go binary + a styles directory
Monthly cost: $0 — local binary; CI cost only if you run it in pipelines.

Migration sketch. Vale is prose-linter-shaped, closer to ESLint than to Grammarly. Install via `brew install vale` or download the binary; pull a style package (`vale sync` against `.vale.ini` referencing Microsoft / Google / proselint styles). Wire into editor (VSCode `errata-ai.vale-server` extension) or CI for docs PR review.

Good fit forDocumentation teams and devs who want enforceable, repo-checked-in style guides — turn 'use active voice' into a CI check.

Weak atNot for casual prose — wrong shape for in-browser corrections; you write rules, not get sentences rewritten.

In a terminal? npx os-alt grammarly prints this table — how the CLI works →