These two get compared constantly and it is mostly a category error. Grammarly is a proofreader that lives in every text box you type into. ProWritingAid is an editing report you run on a finished draft. They overlap on spelling and grammar and diverge everywhere else.
We ran the same 8,000-word manuscript — a non-fiction chapter, already through one human edit — through both. Here is what each one found and what each one missed.
What both caught
Spelling, doubled words, subject-verb disagreement, missing commas after introductory clauses. On pure proofreading the two are close, and both were right in the large majority of cases. Grammarly was a little more confident with dialogue punctuation; ProWritingAid was more thorough on hyphenation consistency (it flagged that we had written “self-editing” and “self editing” in the same chapter, which Grammarly let through).
If proofreading is all you need, pick on convenience, not accuracy.
Where Grammarly is better
It is everywhere. Browser extension, desktop app, keyboard on mobile, plugins for Word and Google Docs. It catches the typo in the email before you send it. ProWritingAid has integrations too, but it is a tool you go to; Grammarly is a tool that comes to you.
Speed. Suggestions appear as you type and accepting one is a click. For the daily volume of short messages most people write, that friction difference matters more than any feature.
Tone detection for email is more useful than it sounds. It is not sophisticated, but “this reads as blunt” before you hit send has saved people from themselves.
Where ProWritingAid is better
The reports. This is the whole argument. ProWritingAid’s summary report on our chapter told us:
- Sentence-length variation was low in the middle third (a wall of 18–22 word sentences, which explained why that section felt flat)
- “Just” appeared 31 times
- Four paragraphs opened with the same construction
- Two passages had “sticky” sentences — more than 45% glue words — that were slowing the reader
None of those are errors. Grammarly would not flag any of them. But they are exactly what a good line editor would circle, and once you have seen the pacing graph of your own writing you cannot un-see it. Writers who use the reports for a few months start to hear those patterns as they type, which is the point: it teaches you.
Long documents. ProWritingAid handled the full 8,000 words in one pass. Grammarly’s document view works but it is built for a page, not a manuscript.
Scrivener and Word integration for people writing books. Grammarly’s Word plugin is fine; ProWritingAid’s understands chapters.
Where both are worse than you think
The AI rewrite features. Both tools now offer to rephrase, “improve clarity”, or adjust tone with one click. On our chapter, accepting those suggestions made the prose more correct and less good. Distinctive sentences became average sentences. A deliberate fragment became a full sentence. A deliberately long, winding sentence describing a long, winding process got chopped in two.
Use the suggestions as a prompt to look at a sentence, not as a replacement for it. If you accept them wholesale you will end up with the tone every other tool produces, which is the thing our voice guide is about.
Pricing shape
We keep numbers out of comparisons because they go stale, but the shape is worth knowing. Grammarly is subscription-only. ProWritingAid has a subscription and also sells a lifetime licence, which for a book-length project is the cheaper route if you will be editing for more than a couple of years. Both have free tiers that cover spelling and basic grammar; the reports and the rewrites are what you pay for. Dates we last checked are on the tool cards below.
Which one you need
- You write email, documents and messages all day and want fewer mistakes: Grammarly.
- You write long things, edit your own work, and want to get better at it: ProWritingAid.
- You do both: it is not unreasonable to run both — Grammarly for the daily flow, ProWritingAid on the manuscript. Just turn off Grammarly’s rewrite suggestions and leave its spelling on.
- You already use a strong AI drafting tool and edit carefully: you may need neither. Ask the drafting tool for a repeated-words count and a sentence-length breakdown; it is not as good as the reports, but it is free.
Tools in this article
Catching mistakes everywhere you type
Grammarly
Good
- Works inside almost every app and browser
- Fast, low-friction corrections
- Tone detector is useful for email
Not so good
- Suggestions flatten distinctive prose
- Weak on manuscript-level structure
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Deep self-editing reports for long manuscripts
ProWritingAid
Good
- Twenty-plus reports: pacing, repetition, sentence length, dialogue
- Integrates with Scrivener and Word
- Lifetime licence for people who hate subscriptions
Not so good
- Interface is busy
- Reports need interpretation; it will not fix a book for you
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