Most "best AI writing assistant" lists are written for the browser. On a Windows PC, half of your writing happens somewhere else: Outlook, Teams, Word, Slack, a CRM, a ticketing tool, a code editor. So the first question for every tool below is not "how good is the AI" but "where does it work".
Disclosure up front: we make KeyShift, which is number one on this list. We have tried to be fair about the others, and several of them are better than KeyShift at the one thing they were built for.
Quick comparison
| Tool | Works in | Beyond grammar | Free plan |
|---|---|---|---|
| KeyShift AI | Any text field on Windows (and macOS, Android) | Rewrite, translate, summarize, reply, voice, OCR, custom prompts | Yes, 25 AI actions a month |
| Grammarly | Browser, desktop app, supported apps | Tone rewrites on paid tiers | Yes |
| Microsoft Copilot | Word, Outlook, Edge, Windows 11 | Drafting and rewriting inside Microsoft apps | Partly, licence for Microsoft 365 apps |
| ChatGPT desktop app | Its own window | Anything, via chat | Yes |
| Wordtune | Browser extension, Word add-in | Rewrites, tones | Yes, limited |
| QuillBot | Website, browser extension | Paraphrase, summarize | Yes, limited |
| TextCortex | Browser extension, desktop app | Rewrites, chat, templates | Yes, limited |
| Wispr Flow | Any app (voice only) | Dictation with clean-up | Yes, limited |
1. KeyShift AI: one shortcut, every app
KeyShift works at the operating-system level. Select text in any app, press Ctrl+Shift+A, and pick an action: fix grammar, translate, make professional, shorten, summarize, draft a reply. The result replaces the selection. If you are already typing, skip the selection: type keyshift fix grammar after your sentence and press space twice.
What sets it apart on Windows is coverage. The same shortcut works in the Outlook desktop app, Teams, Word, Slack, Notion, VS Code and the internal tool nobody wrote an extension for. It also carries the tools around the writing: voice typing with AI clean-up, text from screen for subtitles and images, a clipboard history with AI actions, and translation in place in 50+ languages.
On Pro you can save your own prompts as actions with hotkeys ("keep it under three sentences, British spelling"), and bring your own OpenAI, Claude or Gemini key, or a local model through Ollama if text must not leave your machine.
Best for: anyone who writes in more than one app and is tired of pasting into ChatGPT. Weakest at: passive, always-on checking as you type; KeyShift does nothing until you ask.
Free plan with 25 AI actions a month. Pro is €5.99 a month or €47.99 a year. Download for Windows.
2. Grammarly: the standard for checking as you type
Grammarly remains the best passive checker. Underlines appear as you type, the suggestions are usually right, and a decade of tuning shows. The desktop app for Windows reaches many native apps, and the browser extension covers the web.
Where it stops: rewriting is a suggestion inside Grammarly's interface rather than an action on your text, tone and generative features sit on paid tiers, and translation is not its job. Many people run Grammarly for the underlines and something else for the rewrite. See our Grammarly comparison.
Best for: native speakers who want mistakes caught silently. Weakest at: rewriting in your own voice, translation.
3. Microsoft Copilot: strong inside Microsoft, invisible outside
If your organisation pays for Microsoft 365 Copilot, you get drafting, rewriting and summarizing inside Word, Outlook and Teams, and it is well integrated. Copilot in Windows 11 and Edge is a chat you can paste into.
Where it stops: the licence. Many people on Microsoft 365 do not have Copilot, and the free Copilot app is a chat window, not an in-place assistant. Outside Microsoft apps it does not exist. See AI for Outlook without Copilot and AI for Word.
Best for: companies that have bought the licence. Weakest at: everything outside Office.
4. ChatGPT desktop app: the best chat, the worst shape for editing
The ChatGPT app for Windows is excellent for thinking, research and long conversations. For the fiftieth time today you need a sentence fixed, it is the wrong shape: copy, switch, paste, ask, copy, switch, paste.
Where it stops: there is no in-place editing in other apps. Most tools on this list exist to remove that round trip. See the ChatGPT alternative for when you are already typing.
Best for: conversations and research. Weakest at: quick edits in the app you are in.
5. Wordtune: good rewrites, mostly in the browser
Wordtune rewrites sentences well and offers a handful of tones. It lives in a browser extension, a web editor and a Word add-in.
Where it stops: desktop apps outside Word, and a fixed menu of tones rather than an instruction you write. See Wordtune compared.
Best for: people who write mostly in the browser and want several rewrite options to pick from.
6. QuillBot: the paraphrasing box
QuillBot is the tool students know: paste a paragraph, pick a mode, get a reworded version. It also has a grammar checker and a summarizer, as separate tools on the same site.
Where it stops: it is a website and an extension, with word limits per run on the free plan. See QuillBot compared.
Best for: rewording a paragraph you already have. Weakest at: working where you type.
7. TextCortex: a sidebar assistant with templates
TextCortex offers a browser extension and a desktop app with a chat sidebar, templates and personas. It covers a lot of ground.
Where it stops: the surface is large, and most of it lives in its own panel rather than under your cursor. See TextCortex compared.
Best for: people who want a sidebar assistant with many templates.
8. Wispr Flow: voice first, nothing else
Wispr Flow does one job well: hold a key, talk, and clean text appears where your cursor is. If dictation is the whole job, it is a good choice.
Where it stops: it is voice only. Text you already have on screen is not its concern. See Wispr Flow compared, and KeyShift's own voice typing, which includes the same clean-up as one entry point among several.
Best for: people who dictate most of their writing.
How to choose
- You write in many apps, not only the browser: KeyShift.
- You want silent underlines and nothing else: Grammarly.
- Your company bought the Copilot licence and you live in Office: Copilot.
- You mostly dictate: Wispr Flow, or KeyShift if you also edit.
- You mostly paraphrase school work: QuillBot.
Most people end up with two: a passive checker and an on-demand tool. They do not conflict.
Frequently asked
Which of these work offline? None of the cloud tools. KeyShift on Pro can use a local model through Ollama, so your text never leaves the PC; Grammarly and the others need a connection.
Which work on Windows 10? KeyShift (Windows 10 and later), Grammarly, Wordtune, QuillBot, TextCortex and the ChatGPT app. Copilot in Windows needs Windows 11; Copilot in Office depends on the licence.
Is my text used for training? Check each vendor's policy. KeyShift sends text to the AI provider only for the action you ran and does not use it to train models.
Try KeyShift free on Windows: download, no card needed.