LanguageTool is the go-to open-source grammar checker, with a free tier many developers use daily. Premium runs $4.17/mo on the two-year plan (up to ~$9 monthly). Here is what the upgrade actually changes, evaluated specifically for technical writing.
Free vs Premium, Line by Line
| Capability | Free | Premium |
|---|---|---|
| Basic grammar/spelling rules | Yes | Yes |
| Character limit per check | 2,000 | Unlimited |
| Style and tone suggestions | Limited | Full |
| AI paraphrases | 3/day | More |
| Self-hosted server | Yes (core) | Yes |
| Code-aware checking | No | No |
The last row matters most for developers: Premium buys volume and style depth, but the engine stays prose-first on every tier. Pseudo-code in comments, camelCase identifiers, CLI flags still trip the rules the same way.
Who Should Upgrade
Upgrade if you write long documents (the 2,000-character cap is the sharpest free-tier edge) or want the style layer. Stay free if your checks are short snippets and you value self-hosting - it is the only major checker that offers it.
The Alternative Angle: Code-Aware Checking
If most of your writing lives next to code, the tier decision matters less than the engine decision. A code-aware checker such as Lint skips identifiers, commands, and fenced blocks on every tier - including the free one (10 checks/day, no signup). A reasonable setup: LanguageTool self-hosted for prose documents, Lint for anything that lives in a repository.
Try Lint free - and compare the false-positive rate on your own README.
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