The Tool Desk
Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →Harper is a free, open-source grammar checker for English that can check writing in browsers and supported editors. Harper says it processes text on your device; it supports several English dialects, but it is not a multilingual checker. Its browser and editor integrations make it most relevant if you want spelling, grammar, capitalization, and phrasing suggestions within your existing writing workflow.
What Harper checks—and what language it supports
Harper’s official site says it flags spelling mistakes, capitalization, awkward phrasing, and grammar issues. Those are the publisher’s descriptions of the product, not an independent assessment of its accuracy. Harper’s official site
Harper currently supports English, with British, American, Canadian, Australian, and Indian dialects listed in its FAQ. The FAQ says other human languages are planned but gives no release date. Do not choose Harper on the assumption that it can check writing in languages other than English. Harper FAQ Harper on GitHub
Where you can use Harper
Harper offers browser extensions, editor extensions, native apps, a language server, a JavaScript library, and a Rust crate. For most writers, the practical choice is the integration that fits the place where they already write. Harper integrations
#1 Best Overall
Browser extensions
Chrome and Firefox extensions are described as checking text locally. One compatibility issue matters if you write in Gmail: Harper’s FAQ says it will not run there while Gmail’s built-in grammar checker is enabled. Harper FAQ Browser extension documentation
VS Code and other editors
Harper’s VS Code integration uses harper-ls, its language server, and is documented for VS Code and forks including VSCodium and Windsurf. The integration supports dictionaries, code actions, and ignore comments. The project also lists integrations for Obsidian, Neovim, Zed, WordPress, and other editors; check the relevant integration’s documentation for setup and compatibility details. Harper integrations VS Code Marketplace listing
Privacy, cost, and hardware
Harper’s publisher says checks happen on your device and that your text does not leave it. Its Chrome and Firefox documentation makes the same local-processing claim. Google’s Chrome Web Store listing records the developer’s disclosure that it will not collect or use user data. These are publisher and store disclosures, not an independent privacy audit; if your writing is sensitive, review the extension’s current permissions and applicable privacy information before installing it. Harper privacy information Browser extension documentation Chrome Web Store listing
Harper’s FAQ says the software is free, requires no credit card, and is available under the Apache-2.0 license. It also says no GPU or special hardware is required. An individual browser or editor integration may still have its own compatibility requirements. Harper FAQ Harper on GitHub
How fast is Harper?
Harper’s site claims suggestions arrive in under 10 ms, and the VS Code Marketplace describes feedback as happening “in milliseconds.” The reviewed material does not provide independent benchmark methods or results, so treat these as product claims rather than verified head-to-head speed measurements. Harper’s site also reproduces a testimonial from Rich Edmonds, identified there as Lead PC Hardware Editor at XDA Developers; that endorsement is not a controlled test. Harper performance claim and testimonial VS Code Marketplace listing
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Chrome Web Store listing snapshot
The Chrome Web Store listing showed version 2.10.0, updated September 9, 2026, a size of 8.03 MiB, 50,000 users, and a rating of 4.2 out of 5 from 117 ratings when accessed October 4, 2026. Store figures can change and are not a measure of editing accuracy. Chrome Web Store listing
Who should consider Harper?
Harper is a reasonable option to try if you want a free English checker that integrates with your browser or editor, and you value the publisher’s local-processing approach. It is a poor fit if you need checks for other languages or expect it to run in Gmail alongside Gmail’s own grammar checker. When comparing it with another checker, focus on language coverage, whether it fits your workflow, how its suggestions suit your writing, and the privacy disclosures—not on unverified speed or accuracy comparisons.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
Quick wins for a faster PC:
Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Clear out junk files and repair common Windows errorsFree Scan →
