Grammarly checks whether your writing is correct. ProWritingAid checks whether it's good. That's an oversimplification, but it captures the real difference between these two tools better than any feature list: one is built for fast, everywhere-you-type correction, the other is built for writers who want to understand and fix the patterns in their own prose.
What Grammarly actually does
Grammarly's free tier catches basic grammar, spelling, and punctuation errors anywhere you type online, Gmail, Google Docs, LinkedIn, Slack, most web forms, through a browser extension plus desktop apps for Mac and Windows. Pro runs $12/month and adds full-sentence rewrites, tone adjustment, and AI writing prompts. Business costs $15/user/month and adds team features and brand tone settings for organizations that want consistent voice across multiple writers.
The real value is coverage. Grammarly works in the background across nearly every app you already use, so corrections show up wherever you're actually writing rather than requiring you to paste text into a separate tool. For someone writing emails, Slack messages, LinkedIn posts, and the occasional document across a normal workday, that ambient coverage is the entire point.
The tradeoff is depth. Grammarly's AI writing features are noticeably less capable than dedicated tools like Claude or ChatGPT for generating long-form content, and heavy reliance on its rewrite suggestions tends to push writing toward a homogenized, corporate-safe style that can flatten a writer's actual voice. Reddit writing communities consistently note Grammarly gets over-aggressive about stylistic suggestions that were actually intentional choices, correcting rhythm and sentence variety that a writer put there on purpose.
What ProWritingAid actually does
ProWritingAid's free tier caps at 500 words per check, useful for short pieces but limiting for anything longer. Premium costs $10/month, or $79/year, or a one-time $399 lifetime license for writers who'd rather avoid a recurring subscription entirely, a genuinely rare option in this category. Premium Plus runs $12/month and adds plagiarism checking on top of everything in Premium.
What that price buys is depth Grammarly doesn't attempt: more than 20 report types covering sentence length variation, overused words, pacing, dialogue tags, clichés, redundancies, and full structural analysis that maps chapter and section flow for longer manuscripts. The overused-words report specifically flags a writer's personal crutch phrases, the words and constructions they lean on without noticing, which is a genuinely different kind of feedback than grammar correction.
Integration with Scrivener is a real differentiator: Grammarly doesn't support Scrivener at all, and for novelists and long-form writers who draft there, that's often the deciding factor by itself. ProWritingAid also integrates with Microsoft Word, Google Docs, and Chrome.
Where the depth becomes a liability
ProWritingAid's interface is less polished than Grammarly's, and real-time checking can run slower, especially when multiple report types are active on a longer document. The sheer volume of feedback, 20-plus report categories, can overwhelm a business writer who just wants a quick grammar pass before sending an email, which is exactly the use case Grammarly optimizes for.
Grammarly's opposite failure mode is subtler: because it's fast and always-on, it's easy to accept its suggestions reflexively without evaluating whether they actually improve the sentence, gradually training a writer to defer to the tool's judgment on stylistic calls that are genuinely subjective.
Real cost for different writers
A business professional writing emails, reports, and Slack messages throughout the day: Grammarly Pro at $12/month is built exactly for this use case, catching errors across every app without requiring a separate editing pass. ProWritingAid's depth would mostly go unused here, and its lack of ambient browser coverage across every app makes it a worse fit for someone who isn't drafting in a dedicated writing tool.
A novelist or long-form nonfiction writer working primarily in Scrivener or Word: ProWritingAid's $79/year Premium plan, or the $399 lifetime option for anyone planning to write for years, delivers pacing and structure analysis that Grammarly doesn't offer at any price. The $399 lifetime license pays for itself against Grammarly Pro's $12/month rate in under three years, a real consideration for a career writer.
A small editorial or content team needing consistent style across writers: ProWritingAid's Teams pricing around $6/user/month undercuts Grammarly Business's $15/user/month significantly, though Grammarly's brand tone settings and broader app coverage may still justify the premium for teams whose writing happens primarily in email and chat rather than long-form documents.
What actually breaks in practice
Grammarly's failure mode shows up as homogenization at scale. Teams that rely heavily on Grammarly Business's suggested rewrites across many writers can end up with content that reads as generically correct but loses whatever distinct voice made the writing worth reading in the first place, a real cost for any brand or publication that depends on writer personality.
ProWritingAid's failure mode is abandonment from overwhelm. A writer who turns on all 20-plus report types at once, rather than working through them incrementally, often gets buried in feedback and stops using the deeper reports entirely, falling back to just the basic grammar check and leaving most of the tool's actual value unused.
Data handling and where your writing goes
Grammarly processes all typed text in real time on its own servers and states it does not sell user data or use customer text to train models by default, though the browser extension requires broad page access permissions that raise legitimate concerns for anyone working with sensitive or confidential documents. Business and Enterprise plans add enhanced privacy controls beyond the default. Grammarly holds SOC 2 Type 2 certification.
ProWritingAid also processes text on cloud servers for its analysis, with a desktop app offering an offline mode for writers who want to keep drafts off the network. Public documentation on ProWritingAid's AI model training practices is more limited than Grammarly's, and the free tier does not retain text after analysis completes. Both platforms hold SOC 2 certification, but Grammarly publishes clearer, more detailed data handling commitments overall.
Using both together
Plenty of writers use Grammarly and ProWritingAid at different stages of the same project rather than treating the choice as exclusive. A common workflow runs a first draft through ProWritingAid's structural and pacing reports to fix bigger issues, uneven sentence rhythm, overused phrases, chapters that drag, before a final pass through Grammarly for fast grammar and tone correction closer to publication. That sequencing plays to each tool's actual strength instead of asking one tool to do both jobs.
The cost of running both isn't trivial, Grammarly Pro at $12/month plus ProWritingAid Premium at $10/month adds up to $22/month, or the ProWritingAid lifetime license plus an ongoing Grammarly subscription for writers who want the one-time option on the deeper tool while keeping fast correction on tap. For a working writer whose income depends on manuscript quality, that combined cost is often easy to justify against a single missed deadline or a manuscript rejected for pacing issues that better editing would have caught.
Running both simultaneously in the same editor is usually unnecessary and can produce conflicting suggestions on the same sentence. Using them sequentially, structural pass first with ProWritingAid, then a final correctness pass with Grammarly, avoids that friction while still getting the benefit of both tools' actual strengths.
Which one to actually pick
Pick Grammarly if writing happens across many different apps throughout a normal day, business or professional correctness matters more than deep stylistic analysis, and ambient always-on coverage is worth more than depth of feedback.
Pick ProWritingAid if the primary writing is long-form, fiction or nonfiction manuscripts, reports, or anything drafted in Scrivener or Word where pacing and structural patterns matter more than sentence-level grammar, or if a one-time lifetime purchase is worth more than an ongoing subscription.
For writers genuinely torn between the two, both offer functional free tiers, enough to test real writing samples on each platform and see which type of feedback actually changes how the final piece reads before committing to either subscription.