An English grammar checker that keeps you in control.
A grammar checker finds possible spelling, punctuation, and grammar problems for you to review. FrontierTools uses Harper in your browser, highlights individual issues, and lets you accept or ignore suggestions without replacing your entire draft.
Review suggestions, not a rewritten document
Proofreading works best when you can see what changed. FrontierTools marks possible issues in the editor and presents suggestions for the selected issue. You can make a correction, keep the original wording, or ignore a suggestion that does not apply.
A grammar checker does not know every proper noun, specialist term, deliberate stylistic choice, or context. A highlighted passage is a suggestion to inspect, not proof that the author made a mistake. Keep your intended meaning in view and read the surrounding sentence before accepting a replacement.
Check English in the dialect you use
Choose American, British, or Indian English in the preview, then continue to the signed-in workspace. Paste or write your text in the editor and review the highlighted issues. The editor supports undo, so an accepted change can be reversed if you prefer the original.
Use one dialect consistently unless your document has a reason to mix them. This can help avoid unnecessary corrections to familiar spellings. For another language, the Translator can produce a starting translation, but the English grammar checker should not be treated as a multilingual proofreader.
Private checking, with practical limits
Harper runs locally in a browser worker. After the checker assets have loaded, grammar analysis does not send your draft to a model provider. The first visit may take longer while the browser downloads the checker. Your writing is not saved to your FrontierTools account.
Each check accepts up to 2,000 words and 20,000 characters. Split longer material into coherent sections. Grammar suggestions do not verify factual claims, identify all possible errors, assess plagiarism, or replace a final human proofread. Review important work in its full context.
We should of checked this mesage.
We should have checked this message.
Common questions about grammar checker
Does checking upload my text?
The grammar checker processes the text in your browser using Harper. It downloads checker assets, but does not send the draft to an AI provider for analysis.
Can I undo a correction?
Yes. Accepted corrections remain part of the editor’s undo history. You can also ignore suggestions.
Which languages does it check?
This grammar tool checks English, with American, British, and Indian dialect choices. Translation is a separate tool.