Best AI Grammar and Editing Tools

What separates the top AI grammar checkers on this page?

Three tools, three different jobs. Claude scores 8.8 at $20 and is the writer: both editors ranked its technical explainer and long-form draft first, and it held the brief and tone across 1,500 words without drifting. Grammarly scores 8.4 at $12 and is the editor: it caught every real grammar issue our editors flagged in the rewrite brief, and it works in Gmail, Docs, Word, Slack and the browser with no copying between tools. Notion AI scores 7.9 at $10 and is the in-document option: it answers from your own wiki and cites the page it took them from.

Scoring weights explain the gaps. Output quality is 30 points, control and brand voice 20, workflow and integrations 20, accuracy and disclosure 15, value 15. Claude wins on output and voice; Grammarly wins on workflow; Notion AI wins on context if your team already lives there.

What should you check before buying an AI grammar checker?

Start with where you type. Grammarly's strength is that it sits inside the apps you already use. If your writing happens in a chat window and gets pasted into a doc, that advantage shrinks.

Then look at what you need it to do. Grammarly scored 5 as a generative writer in our test — it is an editor first. Claude has no template library or marketing-campaign workflows, and it still produced one unsupported claim across the six briefs. Notion AI's long-form drafting is behind the dedicated tools, and it is only useful if your team is already in Notion.

• Voice: Grammarly suggestions can flatten a distinctive voice if accepted wholesale. Claude's Projects keep a style guide and source documents attached to everything you write.
• Price: $10 for Notion AI on top of a plan you already pay for, $12 for Grammarly, $20 for Claude.
• Accuracy: check how each tool handles claims it cannot source.

Claude — long-form and technical writing

Pick Claude if you write 1,500-word drafts and need the brief and tone held throughout. Projects keep your style guide and source material attached.

Grammarly — editing inside your existing apps

Pick Grammarly if you want your own writing made clearer without leaving Gmail, Docs, Word, Slack or the browser. The free tier is genuinely useful.

Notion AI — writing inside your team's wiki

Pick Notion AI if your team already keeps its documents in Notion and you want summaries, drafts and rewrites without leaving the page.

Claude suits long-form and technical writers who need a style guide and source material held across a whole body of work. Grammarly suits anyone who wants their own writing edited inside Gmail, Docs, Word, Slack and the browser. Notion AI suits teams already working in Notion who want answers cited from their own wiki.