Free Grammar Checker — Professional English Grammar Check Online
or Ctrl+Enter
Fixed text
Paste your text, click Check my text, and get professional grammar feedback powered by Harper — an open-source grammar engine built in Rust. It detects over a hundred English grammar issues: article usage, repeated words, capitalization errors, spelling mistakes, punctuation problems, and more. The tool also produces a corrected version of your text with all fixable issues applied automatically. Your text is sent over HTTPS to belun.app's own API and is never stored or logged.
How it works
- 1 Paste or type your text Click the text area and paste any English content you want to check — an essay, email, social media post, or any plain text.
- 2 Click Check my text Press the button (or Ctrl+Enter) to send your text to the grammar API. Results appear instantly — each issue shows a category label, a clear description, and a suggested fix.
- 3 Review issues and copy the fixed text Each issue includes a line and column number. Below the issue list, the tool shows your text with all fixable errors already corrected — copy it with one click.
How your data is handled
Your text is sent over HTTPS to belun.app's own API server, where Harper processes it. Nothing is stored, logged, or shared with any third party. No third-party AI services are involved.
Frequently asked questions
- What grammar rules does this tool check?
- The tool uses Harper, a professional open-source grammar engine, which checks over 100 English rules — including incorrect article usage (a/an), repeated words, capitalization errors, spelling mistakes, punctuation spacing, and style issues.
- How does the fixed text work?
- After checking, the tool applies every suggestion that has a clear replacement — repeated words, spelling errors, article fixes, punctuation spacing — and shows the corrected text below the issue list. You can copy it with one click.
- Is my text sent to a server?
- Yes — your text is sent over HTTPS to belun.app's own API server, where Harper processes it locally. Nothing is stored, logged, or shared with any third party.
- Why are some suggestions wrong?
- Natural language has many exceptions and context-dependent rules. Harper's suggestions are a starting point — always review them before applying, especially for stylistic choices.
- Can I use this for languages other than English?
- No. Harper is designed specifically for English. Checking text in other languages will not produce meaningful results.