Both get recommended as "the" grammar checker to use, but they're built around different workflows, not a simple better-or-worse split. Grammarly is built for real-time feedback as you type, across your browser, docs, and email. ProWritingAid is built for running a deliberate set of reports over a draft you've already written. Here's what actually differs, and which one fits which kind of writing.
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Grammarly's free tier covers basic grammar, spelling, and punctuation suggestions, plus its tone detector and some conciseness suggestions, across its browser extension, desktop app, Word plugin, and mobile keyboard. The paid tier (branded Grammarly Pro) adds deeper rewrites — restructuring long sentences, adjusting tone and formality, inclusive-language suggestions, vocabulary variety, and a built-in plagiarism checker that scans the web and academic databases.
ProWritingAid also offers a free way to try it, with a more limited version of its report suite than the paid Premium plan unlocks. Pricing and exact limits on both tools' free tiers shift with promotions and plan changes on both sides, so check each company's current pricing page rather than treating any specific number as fixed for long.
Grammarly is built to interrupt you while you're writing — underlines appear as you type, and most suggestions are a one-click accept or dismiss. That's genuinely useful for catching mistakes before you forget what you meant to write, but it's a narrower set of categories than a dedicated revision tool offers.
ProWritingAid's pitch is the opposite: more than 20 separate writing reports — covering things like overused words, sentence-length variation, sticky sentences, readability, and style issues — meant to be run over a complete draft and worked through deliberately rather than glanced at in passing. That makes it a better fit for revising something long-form, like a thesis chapter or a dissertation draft, where you want a structural pass across the whole thing rather than line-by-line feedback while composing.
Plagiarism checking splits the two tools in a way worth knowing before you pick one for a graded paper: Grammarly bundles it into the paid plan, while ProWritingAid sells it separately as credit packages rather than including it in standard Premium. If catching accidental overlap with a source is the actual reason you want one of these tools, that's a real cost difference, not a footnote.
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