Short answer: October 2026
Grammarly’s humanizer is free and is designed to make AI text sound natural; Grammarly says it “is not intended to bypass AI detectors”. Walter Writes AI is a paid humanizer with a one-time 300-word trial and settings built around detection, including three bypass levels. Grammarly also offers grammar checking, custom voice profiles and a free AI detector. Walter offers an API, an MCP server for AI assistants and fixed monthly word allowances. Neither output was measured here.
| Criterion | Walter Writes AI | Grammarly |
|---|---|---|
| Stated purpose | Rewrite AI text; bypass level setting (Simple, Standard, Enhanced) | Make AI text sound natural; “not intended to bypass AI detectors” |
| Free access | One-time 300 Humanizer words | Free humanizer page; Humanizer agent for free accounts |
| Voice controls | Readability level and purpose settings | Four voices plus custom voice profiles from a 200-word sample |
| Languages | 80+ listed on pricing page | Humanizer agent in six languages |
| Usage limits | Monthly word allowance; 750 to 2,000 words per request | Humanizer limits not published; free plan has 100 AI prompts per month |
| AI detector | Built-in detector on all plans | Free AI detector page; detection listed as a Pro feature in plans |
| Your text and training | Humanized results saved as account documents | Individual accounts used for product improvement and training by default; opt-out available |
| Developer access | API, MCP server, Zapier actions | Not compared here |
| Other writing tools | Detector, paraphraser, grammar checker | Grammar, clarity and other writing agents |
| Measured output quality | Not measured here | Not measured here |
Which should you use: Walter Writes AI or Grammarly?
Start with what you need. If you want an AI draft to sound like your own voice and you already use Grammarly, its free Humanizer agent and custom voice profiles are the obvious first test. If you need a dedicated humanizer with predictable monthly word limits, bypass-level controls, an API or use inside Claude and other AI assistants, Walter is built for that. Grammarly explicitly does not aim at detector scores. Whichever you test, compare the rewrite with your original for changed facts and qualifications.
Is Grammarly’s AI humanizer free?
Yes, in part. Grammarly’s AI humanizer page says the tool on that page “is free to use and offers basic humanization”. With a free account, the Humanizer agent adds four voices, custom voice profiles and six languages; Grammarly says Pro unlocks “the full Humanizer experience”. Its Humanizer user guide lists the agent for Free, Plus and Pro subscribers in Grammarly’s docs surface and Superhuman Go. Grammarly’s plans page lists 100 AI prompts per month on the free plan; it does not publish a separate humanizer limit.
Is Walter Writes AI free?
Only as a trial. Walter’s trial article describes 300 Humanizer words once, with no credit card. After that, Walter’s paid plans provide monthly word allowances with per-request caps of 750 to 2,000 words. The free-trial guide has the details.
How do they treat AI detectors?
They take opposite positions. Grammarly says its humanizer “is not intended to bypass AI detectors”, and its AI detector page, while advertising its own accuracy figure from a public benchmark, also says “No AI detector is 100% accurate.” Walter’s humanizer has a bypass-level setting, and its help center says “Walter rewrites for detection, not for meaning.” Section 26 of Walter’s Terms says it does not support circumventing educational AI detection put in place to prevent academic misconduct. A detector score does not show whether a text is accurate or permitted.
What happens to your text?
Grammarly’s trust page says you can opt out of allowing your content to train its models, and its training control article says the setting is on by default for individual users and off by default for sales-purchased business and all education accounts. Walter’s help center says each humanized result is saved as a document in your account, which you can delete; its privacy policy does not give a specific retention period for submitted text. Check both before uploading sensitive work.
Methodology and evidence limits
This comparison uses only each vendor’s own pages, read on October 15, 2026: Grammarly’s humanizer, detector, plans and trust pages and two support articles, and Walter’s pricing page, Terms of Service and help articles. No outputs were generated and no detector was run, so there is no quality, accuracy or bypass score. Grammarly’s detector accuracy figure is its own claim and was not verified. For more options see the humanizer comparison, the Walter vs QuillBot guide and Walter alternatives.