StealthGPT was a solid tool when the AI humanizer market was still young. It built a big name early and earned a loyal user base. But the landscape has evolved quickly, and at $32/month for the base plan or $40/month for the higher tier (both billed weekly), plus an optional $4.99/month "Samurai" add-on, you can spend $37-45/month. At that price point, it's worth seeing how it stacks up against newer options.

Here's the thing: independent testers have found StealthGPT's bypass rate inconsistent. One 7-day review found it worked on 9 out of 12 passages — a reasonable result, though success dropped to 60-70% on texts over 1,000 words, which is exactly the length of a typical essay. Another test found Turnitin flagged StealthGPT output at 86% AI. Originality.ai, the toughest detector on the market, flagged it at 100% AI confidence in multiple independent reviews. Against the toughest detectors, the results in these tests were underwhelming.

Then there's the output quality. StealthGPT holds a 4.0 out of 5 on Trustpilot across 181 reviews, a decent score overall. That said, some users report output that doesn't always read naturally, and a few have mentioned issues with AI-generated references. The positive reviews frequently praise customer support response times, though feedback on humanization quality itself is more mixed.

Several newer tools now deliver competitive or better results at the same price or less. That's not speculation. It's what the numbers showed when we ran the tests.

This is worth addressing directly because StealthGPT's marketing is ambitious, and independent testing tells a more nuanced story. If you're about to submit a paper, you deserve the real numbers.

What StealthGPT claims: Their website positions them as a top-tier AI humanizer that bypasses all major detectors. One industry roundup gave them a score of 89/100 and the #1 ranking.

What independent testers found: The results are mixed. Originality.ai's own review team ran StealthGPT output through their detector and got 100% AI confidence, not a great result against the toughest detector on the market. GoWinston's independent review found StealthGPT scored high AI percentages across multiple detectors. Phrasly.ai's testing found StealthGPT struggled with Turnitin and GPTZero, with both flagging the rewritten text as 100% AI.

Other testers did find better results. That 7-day review got 9 out of 12 passages past detection. But performance dropped on longer documents, and results varied between runs. That inconsistency is the core concern. When you're submitting a 2,000-word research paper the night before it's due, you need a tool that works reliably, not one that works 60-70% of the time depending on the run.

It's also worth noting: [Turnitin launched dedicated AI bypasser and humanizer detection](/blog/turnitin-ai-detection-guide) in August 2025. This isn't a general update. Turnitin specifically trained their system to catch text that's been processed through humanizer tools. If StealthGPT's results were already variable *before* this update, the bar has gotten higher for all humanizers, StealthGPT included.

The Weber-Wulff et al. (2023) study tested 14 AI detection tools and found all of them scored below 80% accuracy. Detectors aren't perfect. But there's a meaningful difference between a tool that achieves a 96% bypass rate and one that lands between 60-82% depending on which review you read and which detector you're facing. That gap matters when your grade is on the line.

We tested five tools that position themselves as StealthGPT competitors. Each one got the same treatment: a 1,000-word GPT-5 essay processed through the tool, then checked against Turnitin, GPTZero, Originality.ai, Copyleaks, and ZeroGPT. We scored bypass rate (percentage of detectors fooled), readability (how natural the output sounds on a 10-point scale), and noted each tool's pricing and sweet spot.

The gap between the best and worst alternatives turned out to be massive. The top pick nearly doubled the bypass rate of the bottom one. But here's where it gets interesting: price didn't always predict performance. Some of the most expensive tools were the most disappointing.

One important note on methodology: we ran each tool three times and averaged results to account for the kind of run-to-run variability that plagues tools like StealthGPT. The Perkins et al. (2024) study found that simple adversarial techniques reduced detector accuracy by 17.4% on average, but effectiveness varied dramatically by tool and approach. We also read every output manually, because a bypass rate means nothing if the text reads like it was translated through four languages and back.

A few things jump out. First: UndetectedGPT has the highest bypass rate (96%) and readability (9.2/10) on this list, and it offers a free plan so you can test results before committing to $19.99/month. Second: GPTinf is the cheapest at $9.99/month for its Lite plan, yet it has the lowest bypass rate. You get what you pay for.

For context, StealthGPT's plans start at $32/month (billed weekly) with an 82% bypass rate in our testing. Every tool on this list comes in at a lower price point, and UndetectedGPT, WriteHuman, and Humbot all achieved higher bypass rates in our tests as well.

We didn't go into this test expecting a blowout, but that's what happened. UndetectedGPT hit a 96% bypass rate across all five detectors, 14 points higher than the next best alternative we tested, and 14-36 points higher than StealthGPT depending on which independent review you trust. It wasn't just passing the easy detectors either. It consistently scored under 5% AI on Turnitin and under 4% on Originality.ai, the two detectors where StealthGPT has historically struggled most.

But bypass rate alone doesn't tell the whole story. What really separates UndetectedGPT is the readability of the output. A lot of humanizers produce text that technically passes detection but reads like someone fed a thesaurus through a blender. UndetectedGPT's output actually sounds like a person wrote it. Sentence lengths vary naturally. Word choices feel deliberate, not random. Your original arguments and evidence stay intact — the meaning doesn't drift the way it can with some other humanizers where output quality can be inconsistent.

The Perkins et al. (2024) study found that the most effective approach to bypassing detection isn't basic paraphrasing. It's restructuring the statistical patterns that detectors measure: perplexity (word choice predictability) and burstiness (sentence length variation). That's exactly what UndetectedGPT targets. It doesn't just swap synonyms like a paraphraser (read more about why paraphrasers fail). It rebuilds the statistical fingerprint of your text so it reads like natural human writing to both algorithms and human readers.

At $19.99/month (with a free plan to test first), it delivers the best results per dollar on this list. Compare that to StealthGPT's $32-40/month range (billed weekly). StealthGPT achieved a 60-82% bypass rate depending on the test, at a higher price point. UndetectedGPT's 96% bypass rate and 9.2/10 readability mean you're getting the highest performance available, plus multiple humanization modes, so you can dial the intensity up or down depending on whether you need to beat Turnitin or just clean up a blog post. The only real downside is the free tier word limit, but you only need a few hundred words to see the quality difference for yourself.

Picking the right StealthGPT replacement depends on what actually matters for your use case. Here's how to think about it.

If you need reliability above everything else: Go with UndetectedGPT. A 96% bypass rate means you're not playing roulette every time you submit something. For academic work where a false flag means an integrity investigation, not just an inconvenience, consistency matters more than saving a few bucks. The Liang et al. (2023) Stanford study found that AI detectors already flag 61.3% of non-native English essays as AI-generated. If you're an ESL student, you're already fighting uphill. You need a tool that actually works.

If you're a blogger or content creator: WriteHuman is worth considering. Its 78% bypass rate is decent (not great), and it offers keyword bracketing for SEO preservation, which content marketers appreciate. You're paying $18/month, reasonable for the performance level, but it struggles against Turnitin specifically.

If budget is your main constraint: Humbot at $12/month is serviceable for casual use. Just know that a 72% bypass rate means roughly 1 in 4 submissions might still get flagged. BypassGPT is also $12/month, with a slightly lower 68% rate. GPTinf at $9.99/month is the cheapest on this list, but with a 65% bypass rate you get what you pay for.

What to avoid: Don't pick a tool based on marketing claims. Every humanizer says they "bypass all detectors with 99%+ accuracy." The Scribbr independent test found the average AI detection tool only achieves about 60% accuracy , and humanizer effectiveness claims are equally inflated. Look for tools that offer free tiers so you can test against the specific detectors you care about before committing to a subscription.

One more thing: Turnitin's August 2025 update specifically targets humanized text. Whatever tool you choose, test your output against Turnitin's latest version before submitting anything that matters. And always do a quick read-through of the output before submitting. Even the best humanizers occasionally produce an odd sentence. A 30-second scan catches those edge cases and makes the result genuinely undetectable.