Best AI Grammar Checkers of 2026
Five grammar checkers ranked on free plan limits, language coverage, document length, plagiarism checks and price, from each vendor's own pages.
By , research by the BestBots team ยท Updated Oct 18, 2026
Fact checked against each company's published pricing, documentation and verified user ratings. How we score
Grammarly is the best AI grammar checker for most people: free checks in 23 languages inside the apps you already use, and Pro at $12 per month on annual billing for rewrites, tone and plagiarism. QuillBot is the best value at $8.33 per month with plagiarism included, and ProWritingAid is best for book length documents.
Our top picks
How to choose
A grammar checker earns its keep on five points. Check each against how you write.
- Where it works. Do you want errors underlined in Gmail, Word and Slack as you type (Grammarly, QuillBot and Wordtune extensions), or are you happy pasting text into a tool (ChatGPT, QuillBot web)?
- Languages. Grammarly covers 23 for spelling and grammar. QuillBot covers 6. ProWritingAid is English only. If you write in Polish, Korean or Hindi, this decides it.
- Document length. Free plans cap length: ProWritingAid Free at 500 words per report, QuillBot Free paraphrasing at 100 words. ProWritingAid's paid plans check any length.
- Plagiarism. Included on Grammarly Pro and QuillBot Premium; an extra cost on ProWritingAid; absent from Wordtune and ChatGPT.
- Billing term. Every paid checker here is much cheaper annually. Grammarly is $30 monthly vs $12 annually; ProWritingAid $30 vs $10.
Our picks, in detail
- Starting price
- $30 per month
- Free plan
- Yes
- Plagiarism checker
- Pro and up, against 16 billion+ web pages and ProQuest academic papers
- Languages
- Spelling and grammar in 23 languages; advanced suggestions in English, Spanish, French, German, Portuguese and Italian
Grammarly checks spelling and grammar in 23 languages on its free plan and works inside browsers, Word, Outlook, Google Docs and Windows and Mac apps. Pro adds full sentence rewrites, tone adjustment and plagiarism checks for $12 per month on annual billing, and Grammarly publishes SOC 2, HIPAA and FedRAMP.
Pros
- Free plan covers spelling and grammar in 23 languages
- Pro drops to $12 per month on annual billing
- Plagiarism check against 16 billion+ web pages and ProQuest papers
- SOC 2 Type 2, ISO 27001, ISO 42001, HIPAA and FedRAMP listed
- Opt out of model training in account settings
Cons
- $30 per month on monthly billing, 2.5x the annual rate
- Free plan has no plagiarism check and only 100 AI prompts
- Trustpilot score of 3.1 with recurring billing and pop up complaints
- Paragraph rewrites limited to 6 languages
Skip it if you pay monthly, where Pro is $30, or need advanced suggestions in languages beyond its 6 main ones.
- Starting price
- $19.95 per month
- Free plan
- Yes
- Plagiarism checker
- Premium, 25,000 words per month in 100+ languages; more words can be bought
- Languages
- Paraphrase in 23 languages, grammar in 6, translation into 40+
QuillBot Premium costs $8.33 per month on annual billing and pairs advanced grammar suggestions with a paraphraser, summarizer, AI detector and 25,000 plagiarism words a month. Its 4.8 Trustpilot score from 14,537 reviews is the best here.
Pros
- $8.33 per month on annual billing, the cheapest full toolkit here
- 25,000 plagiarism words per month included
- 9 paraphrase modes plus unlimited custom modes
- 4.8 on Trustpilot from 14,537 reviews
- Pause your subscription instead of cancelling
Cons
- Free plan caps paraphrasing and humanizing at 100 words
- Monthly billing costs 2.4x the annual rate
- Grammar checks cover only 6 languages
- Security certifications not published on pages we could open
Skip it if you write in languages other than the 6 its grammar checker supports.
- Starting price
- $30 per month
- Free plan
- Yes
- Plagiarism checker
- Extra cost on every plan
- Languages
- English only (US, UK, Canadian, Australian)
ProWritingAid's paid plans check documents of any length and add style reports and chapter critiques. Premium is $10 per month billed yearly, and a $399 lifetime plan ends the subscription.
Pros
- Paid plans check documents of any length
- $10 per month on yearly billing, $399 lifetime option
- Chapter critiques and creative feedback on Premium Pro
Cons
- English only
- Plagiarism checks cost extra
- No refunds on monthly plans
- Trustpilot reviewers complain about credit based extras
Skip it if you write in any language other than English or want plagiarism checks included.
- Starting price
- $6.99 per month
- Free plan
- Yes
- Plagiarism checker
- Not listed
- Languages
- Not published
Wordtune's free Basic plan includes unlimited grammar and spelling corrections plus 10 rewrites a day, with no word cap on checks. Unlimited rewrites cost $9.99 per month or $6.99 annually.
Pros
- Unlimited rewrites for $9.99, or $6.99 annually
- Free grammar and spelling checks with no cap
- 30% off for students and educators
Cons
- No plagiarism checker or brand voice
- Not a long form generator
- Trustpilot reports of iOS feature outages
Skip it if you need plagiarism checks, a style guide or language coverage details, which Wordtune does not publish.
- Starting price
- $8 per month
- Free plan
- Yes
- Plagiarism checker
- Not published
- Languages
- Not published
ChatGPT Free offers unlimited everyday text chats, so you can paste a draft, get corrections and ask why each change was made. That makes it a good tutor for non native writers, at no cost.
Pros
- Widest feature set in one app: chat, images, voice, Work agent, Codex and connectors
- Five consumer price points from $0 to $500 per month, so you can pay for exactly the usage you need
- Business seats at $20 per month annually undercut most rivals' team plans
- Largest review base in the category: 4.8 on the App Store from over 11 million ratings
Cons
- Go plan at $8 carries ads and stays on the smaller GPT-5.6 Luna model
- GPT-6 Pro is capped by weekly allowances even on Pro, per OpenAI's help center
- Plan and model naming (Sol, Luna, Terra, Astra) is hard to follow
Skip it if you want errors underlined as you type in other apps or a plagiarism report.
What it costs
| Checker | Free plan | Monthly | Annual (per month) | Other terms |
|---|---|---|---|---|
| Grammarly Pro | Spelling, grammar, 100 AI prompts | $30 | $12 | Quarterly $60 |
| QuillBot Premium | Basic grammar, 100 word paraphrases | $19.95 | $8.33 | Quarterly $39.95, 6 months $79.95 |
| ProWritingAid Premium | 500 words per report | $30 | $10 | Lifetime $399 |
| Wordtune Unlimited | Unlimited grammar, 10 rewrites per day | $9.99 | $6.99 | 30% off for .edu |
| ChatGPT | Unlimited everyday text chats | $8 (Go), $20 (Plus) | Not listed |
Prices as listed by each vendor in October 2026. For a one semester student, the cheapest paid option with plagiarism is QuillBot's 6 month plan at $79.95, or Grammarly's quarterly plan at $60 for a shorter term. Every writing tool's price is in the Price Index.
Free plan limits compared
| Checker | Grammar and spelling | AI rewrites | Plagiarism | Length cap |
|---|---|---|---|---|
| Grammarly Free | Yes, 23 languages | 100 AI prompts per month | No | None listed |
| QuillBot Free | Basic errors | Paraphrase 100 words at a time | No | 100 words for paraphrase |
| ProWritingAid Free | Yes, English | 10 rephrases per day | No | 500 words per report |
| Wordtune Basic | Unlimited | 10 rewrites per day | No | None listed for grammar |
| ChatGPT Free | Via chat | Unlimited everyday text chats | No | Per message limits |
For most people, Grammarly Free plus Wordtune Basic covers everyday checking at no cost. Add QuillBot Premium only when you need plagiarism checks.
Best grammar checker by writer type
Office workers and managers. Grammarly. Most of your writing happens in email, chat and shared docs, and Grammarly is the only pick here that covers all of them with inline suggestions plus desktop apps for Windows and Mac. Pro's tone adjustment is worth it if you write to clients. Pay annually.
Students. QuillBot or Grammarly. QuillBot is cheaper and adds a summarizer for readings and a citation generator, with 25,000 plagiarism words a month. Grammarly's plagiarism check includes ProQuest academic databases and its Authorship feature records how a paper was written, which helps if a teacher questions AI use. If your school licenses Grammarly, use that.
Non native English writers. Grammarly for fluency suggestions and translation into 19 languages, or ChatGPT if you want each correction explained so you learn the rule. Wordtune is a cheap way to see several natural versions of the same sentence.
Novelists and long form writers. ProWritingAid. Paid plans check whole manuscripts, Premium Pro adds up to 30 chapter critiques a day, and the lifetime plan suits writers who work on books for years. Pair it with Grammarly Free for everyday email.
Writers in languages other than English. Grammarly, with spelling and grammar in 23 languages. Confirm that advanced suggestions cover your language: they are limited to English, Spanish, French, German, Portuguese and Italian.
Teams with a style guide. Grammarly Pro includes 1 style guide and 1 brand tone shared across members at the per member price, and Enterprise allows unlimited. None of the other checkers here list a team style guide on their pricing pages, apart from QuillBot's Team plan, which does not describe one.
AI grammar checker vs AI chatbot
Dedicated checkers and chatbots like ChatGPT or Claude both fix grammar, but they work differently.
Checkers run continuously where you type, flag issues inline and leave the decision to you. They are consistent, keep a style guide for a team, and on paid plans add plagiarism checks. They are best for high volume everyday writing.
Chatbots rewrite whatever you paste and can explain every change, restructure paragraphs and adapt tone for a specific reader. They are better for a final pass on an important document and for learning. They do not see what you type in other apps unless you paste it, and they do not check originality.
Many writers use both: a checker all day, a chatbot for the documents that matter.
Security and privacy
Grammar checkers read everything you type, so security matters more than with most tools.
- Grammarly publishes SOC 2 Type 2, ISO 27001, ISO 27701, ISO 42001, HIPAA and FedRAMP, says it does not sell user content, and lets you opt out of model training in settings. Enterprise adds BYOK encryption and data loss prevention.
- QuillBot offers data control on its Team plan, but we could not verify its certifications from pages we could open.
- ProWritingAid and Wordtune do not list certifications on their pricing pages.
- ChatGPT Business plans state no training on business data by default.
If you handle client, legal or health information, use Grammarly or a business plan with written no training terms.
Red flags
- Headline prices that are annual. Check the monthly price at checkout.
- Trial renewals. Grammarly has Trustpilot complaints about charges after trials. Set a reminder.
- No refunds on monthly plans. ProWritingAid's money back guarantee covers yearly and lifetime plans only, for 3 days.
- Paywalled extras. ProWritingAid charges extra for plagiarism checks, and Trustpilot reviewers complain about credit based add ons.
How we picked
We compared the grammar checkers people search for most and kept those with published pricing and plan limits. For each we read the vendor's pricing, language and security pages in October 2026 and recorded ratings from Trustpilot and the App Store. We ranked on fit for the most readers: free plan usefulness, language coverage, where the checker works, plagiarism checks, price on annual and monthly billing, and published security commitments. LanguageTool, a popular multilingual checker, was left out because its pricing page did not display prices when we checked. Scores follow our published method.
Frequently asked questions
What is the best AI grammar checker?
Grammarly is the best overall: free spelling and grammar checks in 23 languages, suggestions inside every major app, and Pro at $12 per month on annual billing for rewrites, tone and plagiarism checks. QuillBot is the best value, and ProWritingAid is best for long documents.
What is the best free grammar checker?
Grammarly Free for coverage, with spelling and grammar in 23 languages and 100 AI prompts a month. Wordtune Basic for unlimited grammar and spelling plus 10 rewrites a day. ChatGPT Free if you want explanations.
Is Grammarly better than ProWritingAid?
Grammarly is better for everyday writing across apps and languages, with stronger security certifications. ProWritingAid is better for book length documents and fiction, with chapter critiques and a lifetime plan, but it is English only.
Is QuillBot's grammar checker good?
QuillBot's grammar checker covers 6 languages and gives advanced suggestions and tone insights on Premium. It is a solid checker bundled with a paraphraser and plagiarism tool for $8.33 per month annually, though Grammarly is stronger as an always on checker.
Can ChatGPT check grammar?
Yes. Paste text and ask for corrections, and ask it to explain each change. It does not underline errors as you type in other apps, keep a team style guide or check plagiarism, which dedicated checkers do.
Which grammar checker is best for students?
Grammarly for always on checks and Authorship, which shows where text came from. QuillBot for the cheapest bundle with plagiarism checks. Both offer billing terms that cover a semester: Grammarly quarterly at $60, QuillBot every 6 months at $79.95.
Which grammar checker works in other languages?
Grammarly checks spelling and basic grammar in 23 languages, with advanced suggestions in English, Spanish, French, German, Portuguese and Italian. QuillBot's grammar checker covers 6 languages. ProWritingAid supports only English variants.
Are grammar checkers safe for confidential documents?
Grammarly publishes SOC 2 Type 2, ISO 27001, HIPAA and FedRAMP, says it does not sell content and lets you opt out of model training. For other tools, check the vendor's security page before pasting confidential text, and prefer a business plan with no training by default.