Open Source Grammarly Alternatives (Self-Hosted)

These open source Grammarly alternatives check your writing on a server you control or on your own machine, so your text does not have to go to a third-party service. Licenses, stars and last-commit dates below were checked on Oct 27, 2026.

Compare the top picks

LanguageTool is the self-hostable grammar server here. Harper runs offline on your device, and Vale, proselint and textlint are prose linters for docs and CI.

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Quick comparison

Name	License	Language	Docker?	Last commit
LanguageTool	LGPL-2.1	Java	Yes	2026-10-27
Harper	Apache-2.0	Rust	See docs	2026-10-27
Vale	MIT	Go	See docs	2026-10-24
proselint	BSD-3-Clause	Python	See docs	2026-06-22
textlint	MIT	TypeScript	See docs	2026-10-27

License, stars and last commit checked against the GitHub API and repo files on 2026-10-27.

Listings

LanguageTool

Grammar, style and spell checker you can run as a server

LGPL-2.1 · OSIJavaDocker★ 15,201 as of 2026-10-27

LGPL-2.1 per GitHub license metadata. The core is open source; LanguageTool Premium is a separate paid service.

Pros

Self-hosted server works with LanguageTool browser and editor add-ons
Supports many languages

Cons

Java server to run; optional n-gram data is large
Premium-only checks are not in the open-source core

Website Source Deploy on RepoCloud

Last commit (default branch): 2026-10-27 · Last verified: 2026-10-27

Harper

Offline grammar checker that runs on your device

Apache-2.0 · OSIRust★ 17,170 as of 2026-10-27

Apache-2.0 per GitHub license metadata.

Pros

Runs locally, so text stays on your device
Language server and editor integrations

Cons

English only (per README)
Local tool rather than a shared server

Website Source

Last commit (default branch): 2026-10-27 · Last verified: 2026-10-27

Vale

Command-line prose linter with custom style rules

MIT · OSIGo★ 6,293 as of 2026-10-27

MIT per GitHub license metadata. Repo moved from errata-ai/vale to vale-cli/vale.

Pros

Enforce a house style guide in docs and CI
MIT license

Cons

Style linter, not a full grammar checker
Command-line and editor workflow

Website Source

Last commit (default branch): 2026-10-24 · Last verified: 2026-10-27

proselint

Linter for English prose

BSD-3-Clause · OSIPython★ 4,587 as of 2026-10-27

BSD-3-Clause per GitHub license metadata.

Pros

Flags usage and style problems from expert writing guides
Small and scriptable

Cons

Command line, no web interface
Last commit 2026-06-22

Website Source

Last commit (default branch): 2026-06-22 · Last verified: 2026-10-27

textlint

Pluggable linting tool for text and Markdown

MIT · OSITypeScript★ 3,203 as of 2026-10-27

MIT per GitHub license metadata.

Pros

Rule plugins for style, terminology and spelling
Can run as an MCP server (per README)

Cons

Needs rules configured before it is useful
Developer-oriented setup

Website Source

Last commit (default branch): 2026-10-27 · Last verified: 2026-10-27

How to choose

Want browser and editor checks backed by your own server? LanguageTool (LGPL-2.1).
Want checks that never leave your device? Harper (Apache-2.0), English only.
Enforcing a style guide in docs? Vale (MIT), proselint (BSD-3-Clause) or textlint (MIT).

FAQ

Can I use LanguageTool add-ons with my own server?

Yes, the LanguageTool browser and editor add-ons can point to a self-hosted server. See LanguageTool's docs for the setting.

Do these rewrite text with AI like Grammarly?

These tools focus on grammar, spelling and style rules. Check each project for current features.

Which languages are supported?

LanguageTool supports many languages; Harper is English only per its README; Vale, proselint and textlint depend on the rules you install.

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