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APIMaster.ai
Detect fake LLM APIs & reveal the real model underneath
The original idea was simple: I kept wondering – Is this LLM API I’m paying for actually real?? So I built something to answer that question. How does the detector work? I extracted 300+ stylistic features from each model (Opus 4.8 loves saying “genuinely”, “honestly”, and using “I” a lot, for example). Then built a classifier that can tell you what model is actually running behind the API. Based on 1k+ real user tests, 41% of LLM APIs out there are fake.
Hey Product Hunt 👋
I built APIMaster.ai after getting tired of not knowing whether the "Claude Opus" I was paying for was actually Claude Opus.
The obvious check — asking the model "what are you?" — is trivially fakeable. Any reseller can patch a system prompt to make GPT-3.5 swear it's Opus. So I built something that doesn't ask. It measures.
The tool probes behavioral signatures: token-level decision patterns under ambiguity, response structure preferences, characteristic failure modes on adversarial inputs with noise injection. These survive system prompt overrides. To fake them convincingly, you'd have to actually run the real model — which defeats the whole point of cheating.
What the data showed on day 1 (from r/SillyTavernAI, 19K views):
✅ Verified: api.navy (97%), nano-gpt.com (84%), openrouter.ai (84.7%), pi.tokenator.cloud (78%)
🔴 Fraud: api.airforce — serves GPT 5.4 at 100% confidence regardless of what model you request (Opus, Sonnet, Gemini — all GPT 5.4)
🟠 Suspicious: 9 out of 9 "cheap Opus" endpoints in my original batch — all showing probability mass leaking into haiku-4-5, deepseek-v4-flash, and other cheaper models
The tool is free, MIT licensed, no API key storage (use a throwaway key anyway — that's good hygiene with any third-party tool, including this one).
Happy to answer questions about the methodology — especially skeptical ones. The code is open if you want to audit it.
Cheap != Cheat. But verify before you trust.
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About APIMaster.ai on Product Hunt
“Detect fake LLM APIs & reveal the real model underneath”
APIMaster.ai was submitted on Product Hunt and earned 0 upvotes and 1 comments, earning #1 Product of the Day. The original idea was simple: I kept wondering – Is this LLM API I’m paying for actually real?? So I built something to answer that question. How does the detector work? I extracted 300+ stylistic features from each model (Opus 4.8 loves saying “genuinely”, “honestly”, and using “I” a lot, for example). Then built a classifier that can tell you what model is actually running behind the API. Based on 1k+ real user tests, 41% of LLM APIs out there are fake.
APIMaster.ai was featured in Developer Tools (514k followers), Artificial Intelligence (471k followers) and Security (2.7k followers) on Product Hunt. Together, these topics include over 177k products, making this a competitive space to launch in.
Who hunted APIMaster.ai?
APIMaster.ai was hunted by Chuang Ma. A “hunter” on Product Hunt is the community member who submits a product to the platform — uploading the images, the link, and tagging the makers behind it. Hunters typically write the first comment explaining why a product is worth attention, and their followers are notified the moment they post. Around 79% of featured launches on Product Hunt are self-hunted by their makers, but a well-known hunter still acts as a signal of quality to the rest of the community. See the full all-time top hunters leaderboard to discover who is shaping the Product Hunt ecosystem.
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Chuang Ma