If you write for a living, or even if writing is just a regular part of your job, you've probably looked at Grammarly and ProWritingAid at some point. They're the two biggest names in writing assistant software, and on the surface, they look like they do the same thing.
They don't. Not really. And picking the wrong one could mean paying for features you don't use while missing the ones you actually need.
I've used both for over a year across different types of writing. Here's what I found.
The Quick Version
Grammarly is faster, more polished, and works everywhere. ProWritingAid is deeper, more analytical, and better for long-form work. If you want a quick answer, Grammarly is the better daily driver for most people. ProWritingAid is the better tool for serious writers who want to improve their craft.
Now let me show you why.
Grammarly: The Writing Assistant That Lives in Your Browser
What makes Grammarly special isn't any single feature. It's the fact that it works everywhere, all the time, without you thinking about it. Install the browser extension, and it checks your grammar in Gmail, Google Docs, Slack, LinkedIn, your CMS, and basically every text field on the internet.
The corrections are fast and accurate. Spelling, grammar, punctuation, sentence structure. The free version covers the basics well. The Pro plan ($12/month billed annually, $30/month otherwise) adds tone detection, full sentence rewrites, clarity suggestions, and GrammarlyGO, which gives you 2,000 AI-powered writing prompts per month.
GrammarlyGO is a solid addition. You can highlight a paragraph and ask it to make the tone more confident, simplify the language, or expand on a point. It's not a full AI writer, but as a revision tool, it saves real time.
The interface is clean and minimal. Suggestions appear inline, and you accept or dismiss them with a click. There's almost no learning curve. You install it and it starts helping.
ProWritingAid: The Writing Coach You Didn't Know You Needed
ProWritingAid takes a fundamentally different approach. Instead of just fixing errors, it teaches you why something isn't working and shows you patterns in your writing that you might not see on your own.
The 25+ writing analysis reports are the standout feature. You get reports on overused words, sentence length variation, readability, pacing, dialogue tags, sticky sentences (sentences with too many glue words), and more. If you've ever wondered why your writing feels flat even though the grammar is correct, these reports will show you exactly where to look.
For fiction writers, this is a game-changer. ProWritingAid understands narrative structure in a way Grammarly doesn't even attempt. It flags passive voice in action scenes, catches inconsistent pacing, and identifies sections where your prose gets bogged down in unnecessary words.
Pricing is competitive. The Premium plan is $10/month billed yearly ($30 monthly). Premium Pro runs $12/month billed yearly. And here's the kicker: ProWritingAid offers a lifetime license for $399. If you're a career writer, that one-time payment will save you a fortune over the years.
The free plan is limited (500-word checks, 10 rephrases per day), but it gives you enough to see the analysis reports in action.
Where Grammarly Wins
Convenience. Grammarly works in more places with less friction. The browser extension, desktop app, and mobile keyboard mean you're covered no matter where you're writing. ProWritingAid has a browser extension too, but it's not as seamlessly integrated.
Speed. Grammarly checks happen in real time with almost no lag. ProWritingAid's deeper analysis takes a moment to process, especially on longer documents.
Business writing. For emails, Slack messages, social posts, and other short-form professional communication, Grammarly's quick suggestions are perfect. You don't need a 25-report analysis for a two-paragraph email.
Where ProWritingAid Wins
Long-form writing. If you're writing books, in-depth articles, academic papers, or any content over 2,000 words, ProWritingAid's analysis tools give you insights that Grammarly simply doesn't offer.
Writing improvement. ProWritingAid doesn't just fix your writing. It makes you a better writer over time. The reports show you your habits, good and bad, so you can consciously improve. Grammarly fixes the symptom. ProWritingAid addresses the root cause.
Value. The lifetime license at $399 is unmatched. If you plan to write professionally for the next 5+ years, that's less than $7/month amortized. No subscription tool can touch that.
The AI Comparison
Both tools have AI features now. Grammarly's GrammarlyGO offers rephrasing, tone adjustment, and content generation within its interface. ProWritingAid's AI Sparks provide similar capabilities, though with lower daily limits on the free and basic plans.
In practice, GrammarlyGO feels more integrated and natural to use. ProWritingAid's AI features work fine but feel more like an add-on than a core part of the experience. If AI assistance is important to you, Grammarly has the edge here.
Which One Should You Pick?
Choose Grammarly if you write emails, social posts, and short-form content throughout your day and want something that works invisibly in the background. If convenience and speed matter more than depth, Grammarly is the answer. It's also the better choice for teams and business environments.
Choose ProWritingAid if you write long-form content like blog posts, articles, books, or academic papers. If you want to actually improve as a writer (not just catch mistakes), the analysis reports are worth their weight in gold. And if you hate subscriptions, that lifetime license is a beautiful thing.
Or use both. Seriously. Some writers use Grammarly for day-to-day communications and ProWritingAid for their serious writing projects. They complement each other well, and if you use ProWritingAid's lifetime plan, the combined cost is still reasonable.
Try the free versions of each. You'll know within a day which one fits your writing life better.