Introduction
AI detectors and humanizers are evolving fast. The real question is simple: does the output read like something a human wrote, and will the AI detectors you use flag it? I tested five widely used humanizers in 2025: TwainGPT, Phrasly, Undetectable AI, Grammarly, and QuillBot.
TwainGPT
TwainGPT is the best AI humanizer in 2025. It consistently produces natural, undetectable writing that bypasses major AI detectors like GPTZero while keeping the original meaning intact. In testing, TwainGPT scored as 0% AI detected across GPTZero and other major detectors.
The platform includes three tools in one: a humanizer, an AI detector, and an AI writing generator. The interface is clean and runs smoothly in the browser without any setup or plugins.
TwainGPT’s strength is its consistency across multiple AI detectors. It maintains a human-like writing style and sentence structure while achieving the highest bypass rate in every test. It’s fast, reliable, and transparent. You can even check their public TwainGPT Release Notes, where they document updates and improvements for each version.
Pricing is flexible, with a free tier and paid plans available on the TwainGPT Pricing Page. For anyone who works with AI text regularly, the all-in-one setup makes it one of the most reliable and consistent AI humanizers on the market today.
Phrasly AI
Phrasly AI is one of the more polished AI humanizers on the market. It delivers clear, readable results with quick processing and a smooth interface.
In testing, the Phrasly output sounded natural and more coherent than the original, but it didn’t fully bypass detection. On GPTZero, the sample was flagged as 64% AI, showing that it reduced the detection rate but didn’t completely remove AI detection.
The company advertises a “truly unlimited” plan, which means you can theoretically run billions of words through it, though that claim hasn’t been independently tested. It’s not the cheapest option, but it offers stable quality and consistent updates backed by Phrasly’s public release notes.
Undetectable AI
Undetectable AI is one of the biggest names in the AI humanizer market, boasting over 20 million users worldwide. It’s heavily promoted across Google and social media, with claims of being able to fully bypass every major detector.
In testing, however, the results didn’t match the marketing. The output was poorly reworded and still read like standard AI text. On GPTZero, the humanized sample was flagged as 100% AI, showing that it failed to reduce detection even slightly.
The interface is fast and easy to use, and it offers quick humanization presets. Beyond that, there’s limited transparency. The company doesn’t provide model updates or release notes, so users can’t verify when or how improvements are made.
Undetectable AI may dominate in visibility and user count, but its performance doesn’t reflect its scale.
Grammarly
Grammarly is one of the most recognized writing tools in the world, but its focus has always been clarity and correctness, not bypassing AI detection. The platform’s “Generative AI” and rewriting tools are designed to refine writing, not disguise it.
In testing, Grammarly produced polished and professional text, but it still registered as 100% AI on GPTZero. The edits improved flow and structure, yet the detector correctly identified it as AI-generated.
What sets Grammarly apart is its overall writing quality and workflow integration. It runs directly in browsers, Google Docs, and Microsoft Word, offering grammar fixes, tone adjustments, and style recommendations in real time.
Grammarly isn’t a humanizer in the strict sense. It’s a powerful writing enhancer. It’s best for editing, proofreading, and improving AI text readability, not for bypassing AI detectors.
QuillBot
QuillBot has been around for years and remains one of the most popular rewriting tools online. It’s built around clarity and readability rather than stealth, but it still performs decently depending on how the text is processed.
In testing, the QuillBot humanizer sounded natural and well-structured, yet GPTZero still flagged it as 100% AI. The tool focuses on paraphrasing and improving sentence flow instead of removing AI detection, so full bypassing isn’t its strength.
If you want smoother writing that reads better without losing context, QuillBot is a great option. But if you need to consistently bypass AI detectors like GPTZero, stronger humanizers such as TwainGPT perform far better.
Final Thoughts
After testing five of the most popular AI humanizers — TwainGPT, Phrasly, Undetectable AI, Grammarly, and QuillBot — one thing became clear. Most tools promise full AI detection bypassing, but very few actually deliver.
TwainGPT stood out as the best AI humanizer, producing natural, undetectable text that successfully bypassed GPTZero. Phrasly lowered detection somewhat and offers a “truly unlimited” plan that could appeal to heavy users, even if it did not fully pass. The rest of the tools were more suited for rewriting or editing than true humanization.
The AI humanizer space is evolving quickly, but TwainGPT continues to lead with real results and transparent updates. If you want to try it for yourself, you can get started at twaingpt.com.