StealthGPT is an AI humanization tool that's been heavily marketed toward students. The pitch? Paste your ChatGPT output, hit a button, and get back text that slips past AI detectors. It has carved out a niche with college students, which makes sense given its branding. The website leans hard into the academic angle, with testimonials from students and comparisons against Turnitin front and center.

StealthGPT offers different "engines" you can choose between depending on your needs. The standard engine prioritizes speed, while the quality-optimized engine aims for maximum bypass capability. There's also a Samurai Engine add-on ($4.99/mo extra) that claims to boost coherency and beat additional detectors like Winston AI and Copyleaks. The tool also includes a Chrome extension that lets you highlight text on any page, right-click, and have it rewritten in place. That's genuinely convenient.

Pricing starts at $32/month (billed weekly), with a higher tier at $40/month. That's a significant price jump from what StealthGPT used to charge, and it puts them well above most competitors before you even know if it works for your use case.

StealthGPT also had a lifetime deal on AppSumo at $49, though that deal is no longer available. On paper, the feature set looks solid. But we've seen plenty of tools that look great on paper and fall apart under real testing. So let's get into the numbers.

Same process we use for every review. No shortcuts, no cherry-picking. We generated a 1,000-word essay using GPT-5 on a standard academic topic, then ran it through StealthGPT using the quality-optimized engine (since that's the mode most users would pick for important submissions). We checked the output against 5 major AI detectors: Turnitin, GPTZero, Originality.ai, Copyleaks, and ZeroGPT.

We recorded the AI detection score before and after humanization for each detector. Beyond the numbers, we also evaluated whether the output actually read well, because a 0% AI score means nothing if your essay sounds like it was written by a malfunctioning thesaurus. We ran the test three times and averaged the results to account for the natural variability in how these tools process text.

We also tested with the Samurai Engine upgrade to see if the extra $4.99/mo made a meaningful difference. What you see below is the real, unfiltered picture.

The results tell an interesting story. StealthGPT performed well against most detectors, genuinely well. Turnitin dropped to 22% (see our Turnitin AI detection guide for context on thresholds), GPTZero to 18%, and ZeroGPT cratered to just 15%. Those are real passes. If your school relies on any of those detectors, StealthGPT will likely get you through without issues.

But there's a catch, and it's a big one: Originality.ai. StealthGPT only managed to bring that score down to 35%. That's better than a lot of competitors, sure, but it's still firmly in "flagged as AI" territory. Originality.ai uses a different deep learning approach than the other detectors, and StealthGPT's rewriting engine doesn't seem to account for it as well. Independent reviews confirm this weakness. Multiple third-party tests found StealthGPT performs inconsistently against Originality.ai, with some testers reporting even higher scores.

Copyleaks landed at 25%, which is a pass but not by a huge margin. The overall bypass rate across all five detectors comes to roughly 80%, meaning it consistently passed 4 out of 5 detectors but couldn't crack Originality.ai.

The Samurai Engine upgrade improved results slightly (roughly 2-3% lower scores on average), but it wasn't enough to push Originality.ai below the threshold. At $4.99/mo extra on top of an already expensive plan, the improvement didn't justify the cost in our testing.

StealthGPT's website claims it can bypass "all" AI detectors. That's not what we found, and it's not what independent reviewers found either.

A Winston AI review of StealthGPT (run by a competing detector, so take it with appropriate skepticism) found the tool's output was still detectable on their platform. Third-party comparison tests on sites like Ryne AI and WriteHybrid ranked StealthGPT below several competitors, with one test giving it a 7.9/10 overall score. Its main strengths were identified as convenience (the Chrome extension) and decent performance on GPTZero specifically, while its weaknesses centered on inconsistent results, readability drops on longer texts, and limited customization options.

Here's the thing about accuracy claims in this space: every tool cherry-picks the results that make them look good. StealthGPT highlights its Turnitin performance. But they're quieter about Originality.ai. The Perkins et al. (2024) study found that AI detector accuracy across six major tools sat at only 39.5% baseline, dropping further when students applied even basic editing. So the real question isn't whether StealthGPT can sometimes beat a detector. It's whether it can do it consistently, across all major detectors, without destroying your text.

And the honest answer is: sometimes, against some detectors, with some caveats. That's not the same as "unbeatable."

StealthGPT isn't a bad tool. Let's be real about that upfront. It does what it claims to do, most of the time. But "most of the time" isn't good enough when your grade or client relationship is on the line. Here's where it stands:

Here's how StealthGPT stacks up against the two top-performing alternatives in our testing. Same essay, same detectors, same methodology.

We're not going to pretend we're unbiased. We built UndetectedGPT. But the numbers speak for themselves, and we publish them transparently so you can verify.

StealthGPT is a decent tool if you only need to beat Turnitin, GPTZero, or ZeroGPT. The Chrome extension is a genuinely nice feature. The unlimited word count means no surprises on your bill. If your school uses only one of those detectors and you've tested StealthGPT against it specifically, it might work for you.

But here's where the math stops working. UndetectedGPT achieved a 96% bypass rate versus StealthGPT's roughly 80%. On Turnitin, UndetectedGPT scored under 5% compared to StealthGPT's 22% (which is right on Turnitin's visibility threshold). On Originality.ai, StealthGPT's weak spot, UndetectedGPT came in under 4%. The readability gap is real too. StealthGPT's output is fine for basic essays, but it gets shaky with technical language and nuanced arguments. UndetectedGPT preserves meaning and natural flow even on complex topics.

And price? UndetectedGPT starts at $19.99/month versus StealthGPT's $32/month (billed weekly). UndetectedGPT is both cheaper and outperforms on every metric we tested: bypass rate, readability, and meaning preservation. There's also a free tier so you can verify the results yourself before paying.

If you're currently using StealthGPT and getting inconsistent results (we cover more options in our StealthGPT alternatives guide), especially with Originality.ai or borderline Turnitin scores, it's worth running a free test on UndetectedGPT to see the difference for yourself.