Private Writing AssistantPrivate Writing Assistant vs Harper
Updated October 29, 2026
Harper and Private Writing Assistant are both private: their Chrome extensions check your writing on your own computer and send none of it anywhere. The difference is how they check. Harper uses a set of rules for English, with no AI model, so it is fast and runs on any computer. Private Writing Assistant uses Chrome Built-in AI, a language model, to check 101 languages and rewrite text, and needs a computer that can run it.
| Browser extension | Private Writing Assistant | Harper |
|---|---|---|
| What it checks | Spelling, grammar and punctuation, by an AI model that reads the whole sentence | Spelling, grammar, capitalization and awkward phrasing, using rules rather than an AI model |
| Where your text is checked | On your computer, by Chrome Built-in AI | On your computer |
| What happens to your text | It never leaves your computer. Usage stats without any text are on by default and can be turned off | Harper says your writing never leaves your device, with no telemetry |
| Account needed | No | No |
| Price | Free | Free and open source (Apache-2.0) |
| Languages | 101, detected for each sentence | English only (US, UK, Canadian, Australian and Indian) |
| Works offline | Yes, after the one-time model download | Yes |
| Rewriting | Yes, in eight styles, with no limits | No; Harper says it avoids edits that might change your meaning |
| Google Docs | Yes, and Google Slides | Yes |
| Browsers | Chrome 138 or newer | Chrome, Edge and Firefox |
| What your computer needs | 22 GB of free disk space and a graphics card with more than 4 GB of memory or 16 GB of RAM (details) | Nothing special; no graphics card needed |
Facts about the other products were checked on their own pages on October 28, 2026 and are listed under Sources. Prices are in US dollars and can change.
When Harper is the better choice
- You write only in English and want instant checks on any computer, including older ones that can't run Chrome Built-in AI.
- You use Firefox or Edge.
- You prefer open-source software whose code you can read.
- You want a checker that suggests fixes but never rewrites your sentences.
When Private Writing Assistant is the better choice
- You write in a language other than English, or switch languages within a message.
- You want an AI model that reads each sentence as a whole, rather than a set of rules.
- You want to rewrite a selection in one of eight styles, such as shorter or more professional.