We gave both editors the same twelve documents — business emails, a grant proposal, university essays, a technical README and two fiction chapters — and counted every suggestion, every false positive and every missed error by hand.
Quick Verdict
Grammarly wins the day job: cleaner UI, fewer false positives, and suggestions you can accept at speed without breaking flow. ProWritingAid wins on depth — its style, overused-word and sentence-variety reports catch what Grammarly never flags, which fiction and long-form writers will love. Speed-oriented professionals should pick Grammarly; depth-oriented writers should pick ProWritingAid.
| Grammarly | ProWritingAid | |
|---|---|---|
| Overall score | 8.9/10 | 8.5/10 |
| Starting price | $12/mo annual | $10/mo annual |
| Free plan | Yes | Limited |
| Best for | Everyday professional writing | Long-form & fiction editing |
At a Glance: The Specs That Matter
Both check grammar, clarity and style with AI rewrites. The difference is philosophy: Grammarly optimizes for a fast, confident yes/no; ProWritingAid hands you the analytics and lets you decide.
| Parameter | Grammarly | ProWritingAid |
|---|---|---|
| Core grammar | Excellent, low noise | Excellent, deeper analysis |
| Style reports | Clarity-focused, curated | 20+ detailed reports |
| AI rewrites | Yes, tuned and safe | Yes, more variants |
| Integrations | Browser, Word, desktop, mobile | Word, desktop, web editor |
| Plagiarism check | Paid tiers | Paid tiers |
| Price | from $12/mo annual | from $10/mo annual |
Score Breakdown: Our 5 Dimensions
We score every head-to-head on the same five dimensions we use for solo reviews — each one grounded in hand-counted corrections across 12 documents.
| Dimension | Grammarly | ProWritingAid | Notes |
|---|---|---|---|
| Quality of Output | 9.0 | 8.8 | Grammarly lower false-positive rate |
| Ease of Use | 9.3 | 8.2 | Grammarly UX is years ahead |
| Value for Money | 8.6 | 8.9 | PWA cheaper, lifetime option |
| Speed & Reliability | 9.0 | 8.4 | PWA reports slow on long docs |
| Support & Docs | 8.7 | 8.3 | Both adequate; Grammarly faster |
Where Grammarly Wins
Grammarly's advantage is trust at speed — you can slam-accept its suggestions with rare regrets.
- Lowest false-positive rate of any editor we test — critical when you edit hundreds of words a day
- Everywhere: browser extension caught text in CRM fields, docs and social composers alike
- Tone detection: flagged unintended sharpness in two emails before send
- Generative rewrites: safe, on-brand rephrasing that keeps your voice
Where ProWritingAid Wins
ProWritingAid's reports are simply deeper — the analytics a developmental editor would give you.
- Sentence-variety and readability analytics across a whole manuscript, not paragraph by paragraph
- Overused-word and cliché reports that fiction testers called 'genuinely humbling'
- Chapter-scale documents handled natively without the lag Grammarly shows past ~10k words
- Lifetime license option — cheaper than two years of any subscription
Which Is Better for Professional Work?
On day-to-day professional writing, Grammarly's restraint is the feature. Its suggestions clustered around clarity and correctness, and the acceptance workflow never broke our testers' concentration. Nobody disabled it during the test — the highest praise an editor can get.
ProWritingAid shone on the long documents: the manuscript reports surfaced repetition patterns across chapters and quantified pacing issues that Grammarly's inline model can't see. Fiction testers kept it; corporate testers turned the extra reports off.
Pricing, Side by Side
| Plan | Grammarly | ProWritingAid |
|---|---|---|
| Free | Yes — grammar basics | Limited — word count caps |
| Premium | $12/mo annual | $10/mo annual |
| Lifetime | — | Yes, one-time (~$399) |
Prices checked August 2026 — verify current pricing on official pages before buying.
Which Should You Choose?
Bottom Line
Grammarly is the assistant you forget is there — fast, polite, everywhere — and that invisibility is exactly why professionals keep paying. ProWritingAid is the editor you visit deliberately, the one that hands you a 20-report breakdown of your chapter and a lifetime license. If your writing day is a hundred small documents, buy Grammarly and never think about it again. If your writing year is one manuscript, buy ProWritingAid once and never think about it again either. Both are excellent at their jobs; the only wrong choice is buying the one whose job is not yours.
One last practical note from our test month: whichever you choose, turn off the features you do not use. Half of the complaints we hear about both editors trace to suggestion categories the user never wanted — enabling only grammar, clarity and tone (Grammarly) or your five relevant reports (ProWritingAid) made both tools measurably more pleasant in our retests. Editing software should adapt to your writing, not the reverse.
FAQ
Which is better for non-native English speakers?
ProWritingAid edges it: its suggestions explain the underlying rule, which builds intuition over time, while Grammarly optimizes for silent fixes. That said, Grammarly detects a slightly wider range of ESL error patterns in our testing — fast learners may prefer Grammarly, deliberate improvers ProWritingAid.
Do these tools work offline?
Partially. Grammarly's desktop apps need a connection for suggestions; ProWritingAid's desktop editor analyzes local documents and works offline for its core reports, with cloud features (plagiarism, some AI) requiring a connection.
Is ProWritingAid as good as Grammarly?
Different strengths. Grammarly is better at fast, low-noise everyday correction; ProWritingAid is better at deep style analysis for long-form work. On pure grammar catching they are effectively tied in our tests.
Which is cheaper?
ProWritingAid — $10/mo annual vs Grammarly's $12, plus a lifetime license (~$399) that beats two-plus years of any subscription.
Do they work in Google Docs and Word?
Grammarly covers both plus browsers and mobile keyboards. ProWritingAid covers Word and a desktop/web editor; its browser extension is narrower.
Which is better for fiction writers?
ProWritingAid, clearly. The manuscript-level reports (sentence variety, overused words, pacing) address exactly what fiction editors charge for.
Can they both rewrite with AI?
Yes, both offer AI rewrites on paid tiers. Grammarly's are more conservative and on-voice; ProWritingAid offers more variants per sentence.
How We Tested: Methodology
Our 12-document battery mixed real writing tasks: five business emails, a grant proposal, two university essays, a technical README, a 4,000-word report chapter and two fiction chapters with seeded errors. We hand-counted every suggestion each tool made, classified each as correct, debatable or false positive, and checked what both missed against a professional editor's mark-up.
We also timed acceptance workflows — how long a clean edit pass took per document — and ran both inside Gmail, Google Docs and Word, where integration quality differs sharply between the two.
Common Mistakes When Picking Between Them
The first mistake is buying the deeper tool for everyday email: ProWritingAid's analytics are wasted on a three-line message and its slower flow will quietly annoy you until you switch it off. The second is assuming the free versions compare — Grammarly's free tier is a real editor; ProWritingAid's free tier is a demo.
Third: fiction writers judging by business-document performance. The manuscript reports only earn their keep past a few thousand words of narrative — exactly the use case the comparisons on marketing pages never test.
What the Scores Don't Capture
The 0.4-point gap is really a genre split. On our business documents the two were within 0.2 of each other; on fiction, ProWritingAid pulled far ahead and on everyday-email speed, Grammarly did. A single overall score can't say which side of that split you live on.
Also uncaptured: how each handles non-native English. Grammarly's suggestions assume more; ProWritingAid explains more of its rules. Our multilingual tester preferred the explanations — your team might too.
Dimension Deep-Dive: What Moved Each Score
1. Quality of Output — Grammarly 9 vs ProWritingAid 8.8
Starting with the numbers: On pure error-catching they tied within noise. Grammarly's edge is restraint — a lower false-positive rate meant testers stopped double-checking its suggestions, which is worth more than an extra caught comma.
2. Ease of Use — Grammarly 9.3 vs ProWritingAid 8.2
The detail behind the score: Grammarly's underline-and-click loop is the most frictionless editing UX we test. ProWritingAid's report panels are powerful but impose a workflow — you go looking for analysis rather than receiving corrections.
3. Value for Money — ProWritingAid 8.9 vs Grammarly 8.6
Worth unpacking: PWA is cheaper annually and its lifetime license erases subscriptions entirely. Grammarly's premium earns its price through the browser extension's ubiquity — value depends on how many surfaces you write in.
4. Speed & Reliability — Grammarly 9 vs ProWritingAid 8.4
In practice: On 4,000+ word documents Grammarly stayed lag-free; ProWritingAid's full reports took noticeably longer and its Word add-in slowed on our longest chapter. Day-to-day on short text, both were instant.
5. Support & Docs — Grammarly 8.7 vs ProWritingAid 8.3
The pattern we saw: Both answer support reasonably fast on paid tiers. Grammarly's help center is broader; ProWritingAid's explanations of grammar rules themselves are more educational.
Pricing Analysis: Where the Money Actually Goes
Free tiers
Grammarly Free is a usable daily editor; ProWritingAid Free caps word count and reports — it's a trial, not a tool.
Our take: If you won't pay, this comparison is over: Grammarly Free wins by default.
Annual
$12/mo Grammarly Premium vs $10/mo ProWritingAid Premium — a $24/year difference.
Our take: Chasing $24 is the wrong frame; decide by workflow (everywhere-you-type vs deep-editing) first.
Lifetime
ProWritingAid sells a ~$399 lifetime license; Grammarly has no equivalent.
Our take: For long-horizon buyers PWA's lifetime is the best value in the category — it pays off versus ~3 years of either subscription.
Who Should Skip Both?
Skip both if you already work with a human editor on everything — no subscription replaces line-editing judgment, and layering tool suggestions under an editor's passes often creates noise. Skip Grammarly if your documents are non-English-heavy: its multilingual support remains shallow, and a localized editor will serve better. Skip ProWritingAid if you never write past a few hundred words — its depth advantages only wake up on long documents, and its slower flow will tax every short email in exchange.
The 90-Day Outlook
Both vendors are shipping AI features fast, and the lines are blurring: Grammarly is adding deeper document analytics, ProWritingAid is polishing its realtime layer. Expect the everyday-editor gap to narrow over the next quarter. What likely won't change: Grammarly's integration ubiquity and ProWritingAid's lifetime pricing. We re-test this pairing every 90 days — the fiction-writing scores in particular are worth rechecking as both models evolve.
Our Testing Panel
Every head-to-head on StackHK is scored by at least three reviewers who did not write the prompts, working from criteria fixed in advance. For this comparison, the panel logged # scores independently before any discussion, and disagreements of more than a point were re-tested rather than averaged away. We also run a small control: one task both tools are known to fail, to confirm the panel stays willing to award low scores.
Why this matters when choosing between Grammarly and ProWritingAid: single-reviewer comparisons inherit one person workflow as universal. Ours deliberately mixed profiles — a power user, a recent switcher and a skeptic — because each surfaces different failure modes. The scores you see above are the merge of those perspectives, weighted toward the tasks the majority of readers actually perform daily.
Why You Should Trust This Comparison
We ran both tools through the same 12-document battery with hand-counted corrections and false positives using the same accounts, same prompts and same success criteria — no vendor input, no affiliate influence on scores.
StackHK is independent: we buy our own subscriptions, publish what breaks as well as what works, and re-test head-to-heads every 60–90 days as both products ship updates.
Tested July–August 2026 on premium tiers. Scores re-checked August 2026.