Grammarly Review (2026): Free vs Pro, Pricing & 15-Error Test [+ Video]

Grammarly is an AI writing assistant that checks grammar, spelling, punctuation, clarity, and tone in real time across your browser, desktop apps, and mobile keyboard. In 2026 it comes in three plans: Free, Pro (formerly Premium), and Enterprise. Below is our hands-on 15-error benchmark test, pricing breakdown, and honest verdict on when to pay for Pro and when a specialist tool beats it.

Get Grammarly free → Real-time grammar, clarity and tone checks wherever you write. Looking for a deal on Pro? See our Grammarly discount guide or compare Grammarly Free vs Pro.

I have used Grammarly daily across emails, blog drafts, and book chapters for nearly a decade. Because the product has changed substantially over the last eighteen months, I re-tested it against a 15-error seeded draft alongside ProWritingAid, LanguageTool, and our own in-browser tools. For a wider look at the market, see our roundup of the best grammar checkers and the top Grammarly alternatives.

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What Grammarly Is and Who It Is For

At its core, Grammarly is an always-on writing safety net that sits inside every app you use: Chrome, Safari, Firefox, Google Docs, Gmail, Slack, LinkedIn, Microsoft Word, Mac/Windows desktop apps, and iOS/Android keyboards.

The Superhuman & Grammarly Pro Rebrand Explained

Two naming changes confuse longtime users in 2026:

1. Grammarly Premium is now Grammarly Pro. Grammarly retired both the “Premium” and “Business” names and combined them into Grammarly Pro ($12/month billed annually, $20/month quarterly, or $30/month monthly).
2. Parent company rebrand to Superhuman. After acquiring the workspace app Coda (December 2024) and the email client Superhuman (July 2025), Grammarly’s parent company rebranded to Superhuman in late 2025. The Grammarly product, browser extension, and pricing tiers remain intact under the Grammarly name.

Our 15-Error Hands-On Benchmark Test

AI overviews cannot show what actually happens when you paste a messy draft into an editor. We seeded a 250-word test passage with 8 mechanical grammar errors and 7 style/structural flaws and ran it through Grammarly Free, Grammarly Pro, ProWritingAid, LanguageTool Free, and our free in-browser Grammar & Style Checker.

Here is the opening test passage with the first 8 mechanical errors seeded:

Their going to the store, and me and him will definately meet you their at 5pm. Its a long drive but the affects of the traffic was worse then we expected, which we should of planned for.

And here is how all five tools scored across the full 15-error benchmark:

#	Seeded Error / Style Issue	Category	Grammarly Free	Grammarly Pro	ProWritingAid	LanguageTool Free	BAWT Free Checker
1	”Their going” / “meet you their”	Homophone (they’re/there)	Caught	Caught	Caught	Caught	Missed
2	”me and him will”	Pronoun case (“he and I”)	Caught	Caught	Caught	Caught	Missed
3	”definately”	Misspelling (“definitely”)	Caught	Caught	Caught	Caught	Missed
4	”Its a long drive”	Missing apostrophe (“It’s”)	Caught	Caught	Caught	Caught	Missed
5	”the affects of”	Affect vs effect	Caught	Caught	Caught	Caught	Missed
6	”traffic was worse” (plural subj)	Subject-verb agreement	Caught	Caught	Caught	Caught	Missed
7	”worse then we expected”	Then vs than	Caught	Caught	Caught	Caught	Missed
8	”should of planned”	Modal error (“should have”)	Caught	Caught	Caught	Caught	Missed
9	”due to the fact that”	Wordy inflation (“because”)	Caught	Caught	Caught	Caught	Caught
10	”mistakes were made by the team”	Passive voice	Blurred (Pro upsell)	Caught + active rewrite	Caught	Caught	Caught
11	”, however the deadline passed”	Comma splice	Missed	Caught (; however,)	Caught	Caught	Caught
12	42-word multi-clause sentence	Run-on sentence	Blurred (Pro upsell)	Caught + split	Caught	Caught	Caught
13	”Walking down the street, the trees…”	Dangling participle	Missed	Missed	Caught	Missed	Caught
14	said the editor".	US quotation punctuation	Blurred (Pro upsell)	Caught	Caught	Caught	Caught
15	Repeated word 3x in 40 words	Close word echo	Missed	Caught (vocabulary)	Caught (Echoes report)	Missed	Missed
Total	15 Seeded Benchmark Checks	Overall Score	9 / 15	14 / 15	14 / 15	12 / 15	6 / 15 (Style/Structure)

Key Takeaways From the Test

1. Grammarly Free catches 100% of basic mechanical typos (8/8) plus simple wordiness (“due to the fact that”), but it deliberately blurs out passive voice rewrites, run-on sentence splits, and punctuation-inside-quotes under a yellow “Pro suggestion” badge.
2. Grammarly Pro (14/15) and ProWritingAid (14/15) tied at the top, with only one blind spot on Grammarly Pro: it still misses classic dangling participles (“Walking down the street, the trees were green”), which both ProWritingAid and our free Dangling Participle Checker flag.
3. If you don’t want to pay for Grammarly Pro, pairing Grammarly Free (for the 8 mechanical errors) with our free Passive Voice Checker and Run-On Sentence Checker covers 14 of the 15 checks at $0 cost.

Is Grammarly’s AI Detector Accurate & How Grammarly Authorship Works

Two of the fastest-growing questions we get from students and freelance writers are whether Grammarly’s built-in AI detector is reliable and whether using Grammarly causes false positives on Turnitin.

• Grammarly’s AI Detector: Included in Grammarly Pro, it estimates the percentage of text likely generated by an LLM (ChatGPT, Claude, Gemini). In our testing, it is useful as a quick pre-check before submitting freelance or academic work, though like all statistical detectors it can flag stiff, formulaic human prose. Run your draft through our free Signs of AI Writing Checker to strip out the exact vocabulary and participial tails that trigger AI detectors.
• Grammarly Authorship (Your Defense Against False AI Accusations): Available on both Free and Pro inside Google Docs and Microsoft Word, Grammarly Authorship categorizes every sentence in your document by origin: typed by you, pasted from an external source, corrected with standard grammar rules, or generated with AI prompts. If a professor or client questions your draft, you can share a verifiable Authorship report proving you wrote the paper yourself. Read our full guide on what to do when falsely accused of AI writing (and whether Grammarly counts as AI on Turnitin).

Grammarly Free vs Pro Pricing (2026)

Feature	Grammarly Free	Grammarly Pro (formerly Premium)
Price (Annual billing)	$0	$12/month ($144 billed annually)
Price (Quarterly / Monthly)	$0	$20/month quarterly · $30/month monthly
Grammar, spelling & punctuation	Yes (8/8 in test)	Yes
Passive voice, run-on & full-sentence rewrites	Blurred / Paywalled	Unlimited
Tone adjustments & vocabulary echoes	Tone label only	Full one-click rewrites
Plagiarism & AI detector	No	Yes (billions of web pages + ProQuest)
Generative AI prompts	100 prompts / month	2,000 prompts / month
Grammarly Authorship tracking	Yes	Yes
Document length limit	100,000 chars (~15,000 words)	100,000 chars (~15,000 words)

For a full 1-year and 3-year cost breakdown, see our Grammarly Free vs Pro comparison and our Grammarly student discount and coupon guide.

Where Grammarly Falls Short (When to Choose ProWritingAid Instead)

Grammarly has one hard technical ceiling that every book author hits: a 100,000-character (~15,000-word) limit per document, plus no native Scrivener integration. If you are editing an 80,000-word novel or nonfiction book, Grammarly forces you to chop your manuscript into six separate files, and its suggestions frequently try to turn natural fiction dialogue into stiff business prose.

If you write books, read our ProWritingAid review or try ProWritingAid free. It plugs straight into Scrivener, scores your chapters across 25+ fiction-specific reports, and offers a $399 Lifetime plan so you can stop paying annual subscription fees.

Final Verdict: Should You Get Grammarly in 2026?

• Start on Grammarly Free if you want an effortless, accurate spell and grammar checker across your browser, email, and Google Docs, and pair it with our free Passive Voice Checker for style edits.
• Upgrade to Grammarly Pro ($12/mo annual) if you write for work or university every day, want one-click sentence rewrites and plagiarism checks, and need 2,000 AI prompts per month.
• Choose ProWritingAid instead if you write long-form fiction or nonfiction books in Scrivener or Word.

About this guide: Written by Bryan Collins, USA Today bestselling author and founder of Become a Writer Today. Our recommendations are based on hands-on testing and independent research. Become a Writer Today does not accept payment for rankings or recommendations.