Best AI Grammar Checkers in 2026

1. Grammarly — best for all-around grammar and clarity

Grammarly is an AI writing assistant that checks grammar, spelling, punctuation, tone, and clarity, and its defining strength is reach: rather than living in one app, it follows you almost everywhere you type through browser extensions, desktop and mobile apps, and integrations with Microsoft Word and Google Docs. The free tier is genuinely useful — core corrections, tone detection, and 100 AI prompts a month at $0 — which covers most everyday writing. Pro costs $12/month billed annually ($144/year), or $30 month-to-month, and raises the allowance to 2,000 prompts while adding full-sentence rewrites, tone adjustment, plagiarism detection, and AI-text detection. Enterprise is custom-priced with SSO, DLP, and audit logs. It fits anyone who writes across many apps and wants on-the-spot corrections without switching editors. The honest caveat: the cheap $12 price only applies if you commit for a full year, since month-to-month jumps to $30.

2. ProWritingAid — best for long-form and manuscript editing

ProWritingAid pairs a grammar and spelling checker with more than 25 in-depth style reports covering pacing, sentence length, overused words, echoes, sensory detail, and readability grade — far deeper analysis than a typical inline checker. It has repositioned around fiction, adding Chapter Critique and Manuscript Analysis aimed at novelists. The free tier is restrictive: a 500-word check limit with only 2 report runs per day. Premium costs $30/month or $120/year (about $10/month annually) for unlimited word count and the full report suite; Premium Pro adds AI coaching at $36/month or $144/year; and one-time Lifetime licenses run $399 (Premium) and $699 (Premium Pro), rare in this category. It integrates with Microsoft Word, Google Docs, Scrivener, and Apple Pages. It suits novelists, academics, and freelance editors working on book-length documents. The caveat: it is slower and heavier than Grammarly on long files, and its real-time inline checking is noticeably less polished.

3. QuillBot — best budget paraphraser

QuillBot is an AI writing suite built around paraphrasing, with grammar checking, summarizing, AI detection, translation, and an AI chat layered on top. The free tier paraphrases up to 125 words at a time in two modes (Standard and Fluency) with a basic grammar checker at $0 — generous enough for casual rewriting. Premium runs $19.95/month, or about $8.33/month on the annual plan ($99.95/year), and unlocks unlimited paraphrasing across every mode, custom-length summaries up to roughly 6,000 words, and a plagiarism checker covering up to 25,000 words a month. It runs in the browser, as desktop and mobile apps, and as extensions for Chrome, Edge, and Microsoft Word. It best fits students, non-native English writers, and bloggers who rewrite and polish text often and want those tools bundled cheaply. The caveat: the free tier’s 125-word paraphrase cap is quickly restrictive on real documents, and its grammar checking is basic next to Grammarly’s.

4. Wordtune — best for inline rewriting

Wordtune is an AI rewriting assistant from AI21 Labs that focuses on improving text you already have rather than generating it. Its core feature is context-aware paraphrasing: highlight a sentence and it offers several alternative phrasings that keep the meaning while changing wording, length, or tone, alongside grammar and spelling correction and a formal-to-casual tone switcher. The Basic tier is free with 10 rewrites per day, 3 AI summaries per month, and unlimited spelling and grammar checks — no credit card required. Advanced is $6.99/month (about $4.89/month annually) for 30 rewrites a day, and Unlimited is $9.99/month (about $6.99/month annually) for unlimited rewrites and summaries. It works inline through a Chrome and Edge extension inside Gmail, Docs, and LinkedIn, with an iOS app. It suits non-native English writers and professionals polishing short text. The caveat: it outputs in English only, so it cannot refine writing in other languages.

How we picked

All four tools earn their place by correcting, rewriting, or analyzing writing rather than drafting it from scratch — grammar and clarity checking, deep style reports, and paraphrasing — which keeps this list distinct from our broader AI writing tools ranking. We weighed correction and rewrite quality, free-tier generosity, platform reach, and verified price value, ranking each for the job it does best rather than forcing a single winner. Pricing was verified on July 8 2026 against each product’s official pricing page; no tool paid or provided incentives to appear in this list.