Harper is a free, open-source grammar checker that runs entirely on your device. It helps writers, students, journalists, and developers catch spelling mistakes, grammar errors, and awkward phrasing without sending text to a server. It is positioned as the private alternative to Grammarly.[1][2]
Quick verdict
Privacy-sensitive writers and developers who live in their editors will get the most from Harper. Its Rust core checks text locally in under 10 milliseconds, with integrations for VS Code, Neovim, Obsidian, WordPress, and major browsers. The tradeoff is scope: Harper covers core spelling, grammar, and phrasing rather than the full coaching set of large cloud assistants, so writers wanting tone analysis or plagiarism detection should look elsewhere. If keeping your words on your own machine matters more than cloud extras, choose Harper.[1][2]
Key features
Fully local checking Every grammar check runs on your own device, so drafts, notes, and messages never leave your computer during checking.[1]
Sub-10ms suggestions The Rust-powered core returns feedback in under 10 milliseconds, keeping corrections in step with typing instead of lagging behind it.[1][2]
No telemetry and no LLM in the loop The project states there are no cloud round-trips, no telemetry, and no language model processing your writing, removing training-on-your-words concern by design.[1]
Language-server distribution Harper ships as a language server, so any editor with language-server support can offer grammar checking through a standard protocol rather than a one-off plugin.[1]
Editor integrations Documented extensions cover VS Code, Neovim, Obsidian, and Zed plus a WordPress block-editor plugin, placing checks where developers and writers already work.[1]
Browser extensions Add-ons for Chrome, Edge, and Firefox bring the same local checker to webmail, documents, and forms in the browser.[1]
Embeddable libraries A JavaScript library and a Rust crate let other projects build Harper checking into their own tools instead of depending on a hosted API.[1]
Free and open source Harper is free with no paid tier stated, and its repository license file is the Apache License 2.0 text.[1][2][3]
Who will love it
Privacy-first writers drafting sensitive material benefit directly from local-only processing with no telemetry.[1]
Developers in Neovim, Zed, and VS Code get grammar feedback inside the editing workflow via the language server and extensions.[1]
Students and journalists get a free checker that keeps working offline with no connection or subscription.[1]
Who should avoid it
Teams needing admin controls should look elsewhere: no team management, single sign-on, or enterprise plan was documented.[1]
Writers wanting coaching extras such as tone analysis or plagiarism detection will not find them in Harper's documented scope.[1]
Non-technical users wanting one simple app face integration choice and installation per writing surface instead of a single managed product.[1]
How people experience it
One inspected firsthand press report: MakeUseOf writer Oluwademilade Afolabi's January 2026 account of switching from paid Grammarly to Harper. No Reddit or G2 reports were inspected, so no testimonial was selected.
1 cited community source. Single-report press sample, not a prevalence estimate; the reporter's needs may not represent other writers. Vendor-selected homepage quotations were excluded as ineligible. Reddit/G2 collection remains the next research action.
A MakeUseOf writer reported stopping his paid Grammarly subscription after finding the free Harper sufficient for what he actually needs, citing no subscription fees and no sending writing to remote servers.[1]
The same report corroborates Harper's on-device design, its Rust core running in the browser via WebAssembly, suggestions in under 10 milliseconds, and customization such as regional dialects and toggleable rules.[1]
One press report is not a prevalence sample: Reddit and G2 firsthand voices are still missing, and vendor-selected homepage quotations were excluded as ineligible.[1][2]
Alternatives and compatibility
Harper runs wherever its integrations run: VS Code, Neovim, Obsidian, Zed, WordPress, Chrome, Edge, Firefox, and macOS via Harper Desktop, plus any language-server-capable editor.[1]
No catalogue alternative relationship is evidenced yet, so a supported switching comparison against a named incumbent stays pending until an incumbent product exists in the catalogue.[1]
Questions worth asking
What is the best Harper alternative for non-technical users?
No supported alternative is catalogued yet, so no conditional recommendation can be evidenced; resolving the missing catalogue relationship is the blocker before this answer can name a non-technical pick.[1]
Is Harper really no-code?
Checking runs inside browser extensions, editor plugins, and desktop apps with no scripting required; the Rust crate, JavaScript library, and language server exist only for people embedding Harper in other tools.[1]
How much does Harper cost per month?
Harper is free with no paid tier, price, or billing unit stated on its official site as checked in October 2026; there is no per-seat or subscription cost to report.[1]
Can you self-host Harper?
There is no server to host: Harper runs as local apps, extensions, and libraries on the user's own hardware, so each user already runs their own copy rather than deploying shared infrastructure.[1]
Sources and editorial review
Source research. Reviewed on October 11, 2026. Written by Sanjib Sah. AI assisted; reviewed by a human editor.
We have not run or tested this product.
One inspected firsthand press report: MakeUseOf writer Oluwademilade Afolabi's January 2026 account of switching from paid Grammarly to Harper. No Reddit or G2 reports were inspected, so no testimonial was selected. Single-report press sample, not a prevalence estimate; the reporter's needs may not represent other writers. Vendor-selected homepage quotations were excluded as ineligible. Reddit/G2 collection remains the next research action.
- Harper | Privacy-First Offline Grammar Checker
official · Observed October 11, 2026
Identity anchor and primary fact source: positioning, privacy claims, speed claim, and the full integration list used across the article.
- Automattic/harper on GitHub
official · Observed October 11, 2026
Repository identity and Rust-powered implementation evidence; cross-checks the homepage GitHub link.
- Automattic/harper LICENSE
official · Observed October 11, 2026
License evidence: the file is the full Apache License 2.0 text, supporting the Apache-2.0 identifier.
- I stopped paying for Grammarly once I found out there's a free open-source alternative
community · Observed October 11, 2026 · Published January 16, 2026
Firsthand press report by MakeUseOf writer Oluwademilade Afolabi describing a switch from paid Grammarly to Harper; corroborates on-device checking, Rust/WebAssembly core, sub-10ms suggestions, and rule/dialect customization. Paraphrased for analysis; no verbatim quotation taken.
Compared with these products
No explicit proprietary baseline is recorded.