8 Best AI Grammar Checkers in 2026 (Tested & Compared)

8 Best AI Grammar Checkers in 2026 (Tested & Compared)

Quick Answer

Grammarly Premium wins for overall accuracy at $12/mo. ProWritingAid wins for fiction writers at $20/mo. QuillBot wins for paraphrasing at $8.33/mo. Free options include Grammarly Free and LanguageTool. Most tools cost $12-30/mo for unlimited checks.

Key Takeaways

• Grammarly Premium: 19/20 errors detected, $12/mo (best overall)
• ProWritingAid: 17/20 errors, 25 fiction reports, $20/mo
• QuillBot: best paraphraser at $8.33/mo
• Free options: Grammarly Free and LanguageTool

How We Tested

We tested 8 grammar checkers on the same 500-word essay containing 20 deliberate errors across four categories: subject-verb agreement, comma splices, tense errors, and awkward phrasing. We scored each tool on:

• Error detection rate (out of 20 planted errors)
• False positive rate (flagged correct text as wrong)
• Writing style suggestions (tone, clarity, conciseness)
• Price per month (annual billing)
• Platform support (web, browser extension, desktop, Google Docs)
• Setup time (how long to start using)

All tests were run with default settings. We did not customize rules to favor any tool.

#1: Grammarly — Best Overall

Grammarly detected 19 out of 20 planted errors with zero false positives. Its Premium plan adds tone detection, clarity rewrites, vocabulary suggestions, and a plagiarism checker. The browser extension works in Gmail, Google Docs, LinkedIn, Twitter/X, and virtually every web text field.

Pricing: Free (basic) / $12/mo Premium (annual) / $15/mo Premium (monthly) / $15/mo Business

Strengths:

• Best-in-class error detection (95% in our test)
• Real-time browser extension across all sites
• Tone detector and goal-oriented writing feedback
• Deep Google Docs integration
• GrammarlyGO for AI rewrites (included in Premium)

Weaknesses:

• Browser extension slows down page load on heavy sites
• Premium is required for advanced rewrites and plagiarism
• Some style rules feel rigid for creative writing
• No self-hosted option

#2: ProWritingAid — Best Fiction

ProWritingAid detected 17 out of 20 errors but offers 25 detailed writing reports that are gold for novelists. Reports include pacing analysis, dialogue tag variety, sentence length distribution, sticky sentence detection, and overused words.

Pricing: Free (basic) / $20/mo Premium / $120/year / $240 lifetime

Strengths:

• 25 in-depth writing reports (unique to this tool)
• Native Scrivener and Google Docs integration
• Fiction-specific analysis (pacing, dialogue, sensory detail)
• One-time lifetime deal available
• Video tutorials for each report

Weaknesses:

• UI feels dated compared to Grammarly
• Steep learning curve (25 reports is a lot)
• Weaker for non-fiction and business writing
• Browser extension is less polished

#3: QuillBot — Best Paraphrasing

QuillBot detected 15 out of 20 errors but its paraphrasing tool rewrites sentences better than any competitor. Seven modes (Standard, Fluency, Formal, Academic, Casual, Expand, Shorten) make it versatile.

Pricing: Free (125 words/paraphrase) / $8.33/mo Premium (annual) / $19.95/mo (monthly)

Strengths:

• Best paraphraser on the market (7 modes)
• Affordable at $8.33/mo
• Built-in summarizer and citation generator
• Chrome extension and Google Docs add-on
• Co-Writer mode for full-document AI writing

Weaknesses:

• Grammar detection weaker than Grammarly
• Free tier limits to 125 words per paraphrase
• No plagiarism checker on lower tiers
• Some rewrites change meaning too aggressively

#4: LanguageTool — Best Free

LanguageTool detected 14 out of 20 errors in its free tier and supports 30+ languages. The open-source core is self-hostable, making it popular for privacy-conscious users.

Pricing: Free (10,000 chars/check) / $12/mo Premium

Strengths:

• Generous free tier (10k characters)
• Supports 30+ languages (best multilingual support)
• Open-source core, self-hostable
• Privacy-focused (EU-based servers)
• Integrates with LibreOffice, Thunderbird

Weaknesses:

• Fewer style suggestions than Grammarly
• Premium not significantly better than free
• UI is functional but not modern
• Plagiarism checker only on highest tier

#5: Wordtune — Best Rewrite

Wordtune detected 12 out of 20 errors but rewrites entire paragraphs with tone options (casual, formal, shorter, longer). It is backed by AI21 Labs and excels at preserving meaning while improving flow.

Pricing: Free (10 rewrites/day) / $24.99/mo Premium

Strengths:

• Beautiful rewrite UI
• Tone control (casual/formal/short/long)
• Works in Gmail, LinkedIn, Google Docs
• Spices feature for creative writing
• Summarizer included

Weaknesses:

• Expensive at $24.99/mo
• Weak pure grammar checking
• Free tier limits to 10 rewrites per day
• No desktop app

Detailed Tool Reviews

Grammarly Deep Dive

Grammarly has three tiers. The free tier catches basic grammar and spelling errors but misses style issues. Premium ($12/mo) adds tone detection, clarity rewrites, vocabulary suggestions, and full-sentence rewrites. Business ($15/mo) adds team style guides and admin controls.

The browser extension is the most polished we tested. It works in Gmail, Google Docs, LinkedIn, Notion, and even Twitter/X. One complaint: the extension adds 200-500ms to page load on heavy sites like Notion.

GrammarlyGO, included in Premium, generates rewrites based on your tone goals (formal, friendly, confident). It is useful but not as good as ChatGPT for creative writing.

ProWritingAid Deep Dive

ProWritingAid's 25 reports include: overused words, sentence length, paragraph length, dialogue tags, pacing, clichés, echoes, and more. Each report shows a score and concrete fixes. The Scrivener integration is seamless for novelists.

The lifetime deal at $240 is the best value for serious writers — you pay once and use it forever.

QuillBot Deep Dive

QuillBot's paraphraser is in a league of its own. Seven modes let you adjust formality, length, and tone. The summarizer condenses articles into key points. The citation generator formats APA, MLA, and Chicago styles automatically.

At $8.33/mo annual, it is the best budget option for ESL writers and students.

LanguageTool Deep Dive

LanguageTool supports 30+ languages including Spanish, French, German, Portuguese, and Russian. The open-source self-hosted version is popular with enterprises that cannot send data to US-based servers.

The free tier handles 10,000 characters per check — enough for most blog posts and emails.

Wordtune Deep Dive

Wordtune's rewrite UI is the most beautiful in the category. Select any sentence and get 4-6 rewrites in different tones. The "Spices" feature adds creative alternatives like "playful" or "confident." It is expensive at $24.99/mo but worth it if you write client-facing emails.

Who Avoid Which Tool?

• Avoid Grammarly if you write fiction (use ProWritingAid) or need self-hosting (use LanguageTool)
• Avoid ProWritingAid if you are a non-fiction writer (25 reports is overkill)
• Avoid Wordtune if you are on a budget ($24.99/mo is steep)
• Avoid Hemingway if you need real-time checking (it is a manual paste tool)

Accuracy by Writing Type

Comparison Table

Pricing

Most grammar checkers discount 40-60% when billed annually. Here is the annual cost comparison:

• Grammarly Premium: $144/year (best value overall)
• ProWritingAid: $120/year or $240 lifetime (best for writers)
• QuillBot Premium: $100/year (best budget)
• LanguageTool: $144/year (best free tier)
• Wordtune: $299/year (most expensive)
• Ginger: $156/year
• Hemingway App: $19.99 one-time (cheapest)

For most users, Grammarly Premium at $12/mo is the best balance of accuracy and price. For fiction writers, ProWritingAid's lifetime deal is worth it.

Who Should Use Which?

FAQs

Is ChatGPT better than Grammarly?

No. ChatGPT is great at rewriting but it is not a real-time grammar checker. You must paste text manually, it misses context-specific rules, and it can introduce new errors. Grammarly checks as you type in Gmail, Google Docs, and every website. For a deeper comparison, see our grammarly alternatives review.

Is Grammarly 100% correct?

No. No grammar checker is. Grammarly missed 1 out of 20 planted errors in our test (a subtle tense consistency issue). Always proofread yourself, especially for high-stakes writing like legal documents or academic papers.

Can ChatGPT check grammar?

Yes, but paste-based only. It catches about 16 out of 20 errors and offers rewrites, but lacks browser integration, real-time suggestions, and Google Docs support. It is best used as a complement, not a replacement.

Which grammar checker is the most accurate?

Grammarly Premium scored highest in our test with 19 out of 20 errors detected. ProWritingAid was second at 17 out of 20. QuillBot was third at 15 out of 20. Free tools range from 9 to 14 out of 20.

Related Articles

• Grammarly Alternatives
• Best AI Writing Tools 2026
• QuillBot Alternatives

Ginger and Hemingway: Honorable Mentions

Ginger Software

Ginger detected 11 out of 20 errors. It is popular with ESL learners for its text-to-speech feature that reads corrected sentences aloud. Pricing is $12.99/month. It falls short on style suggestions and the desktop app feels clunky compared to Grammarly.

Hemingway App

Hemingway detected 9 out of 20 errors but is not really a grammar checker — it is a readability tool. It highlights adverbs, passive voice, and complex sentences in colors. Priced at $19.99 one-time for the desktop app. Best used as a complement to Grammarly, not a replacement.

Which Tool Should You Pick?

For Professionals

If you write for a living (bloggers, marketers, copywriters), Grammarly Premium is non-negotiable. The $12/month pays for itself in the time it saves editing.

For Students

Students should use Grammarly Free or LanguageTool to stay within budget. QuillBot Premium at $8.33/month is worth it for paraphrasing sources.

For Novelists

ProWritingAid is the clear winner. The 25 reports and lifetime deal make it the best investment for fiction authors.

For Non-Native English Speakers

QuillBot's paraphraser combined with Grammarly Free gives you both grammar checking and natural-sounding rewrites for under $10/month.

For Privacy-Conscious Users

LanguageTool's self-hosted open-source version keeps all text on your own servers. No data sent to third parties.

Common Grammar Mistakes We Tested

To make this comparison fair, we deliberately planted 20 common grammar errors in our test essay. Here is what we included:

• Subject-verb agreement errors (e.g., "The team are winning" vs "The team is winning")
• Comma splices (two independent clauses joined by just a comma)
• Tense shifts within paragraphs
• Wrong prepositions (e.g., "depend of" instead of "depend on")
• Apostrophe misuse (its vs it's, plural possessives)
• Run-on sentences
• Sentence fragments
• Word choice errors (affect vs effect, further vs farther)
• Article errors (a vs an vs the)
• Double negatives

We also tested for style issues like passive voice overuse, wordy phrases, and inconsistent tone. Grammarly caught 19 of the 20 planted errors and most style issues. ProWritingAid caught 17 errors but found more style problems across its 25 reports. QuillBot caught 15 errors but excelled at paraphrasing the awkward sentences.

Free vs Paid: Is It Worth Upgrading?

If you only need basic grammar and spelling checking, the free tier of Grammarly or LanguageTool is enough. You will catch most obvious errors before hitting publish.

Upgrade to Premium if:

• You write client-facing content daily
• You need tone detection and clarity rewrites
• You need plagiarism checking
• You write fiction and need style reports

For most bloggers and marketers, the $12/month Grammarly Premium pays for itself within the first week by catching embarrassing errors.

Final Verdict

For most writers, Grammarly Premium at $12/month is the safest choice. For fiction authors, ProWritingAid's lifetime deal at $240 pays for itself within a year. For budget-conscious users, QuillBot at $8.33/month offers the best paraphrasing.

Our top pick for 2026: Grammarly Premium for general writing, ProWritingAid for novelists.

Sources:

• Grammarly Pricing
• ProWritingAid Pricing
• QuillBot Pricing
• LanguageTool Pricing

Last updated: October 2026