OpenAI API Key Checker: How to Verify Your API Provider Is Legit

A complete guide to checking if your OpenAI, Anthropic, or Google API key is connected to a real provider — or a fake relay.

If you purchase API access from a third-party provider, you need an API key checker. The API resale market is full of providers who claim to offer GPT-4, Claude, or Gemini — but actually route your requests to cheaper models while charging premium prices.

Why You Need an API Key Checker

Third-party API providers (also called API relays or API proxies) are intermediaries between you and the original model provider. While many are legitimate, a significant number engage in:

• Model substitution — Claiming GPT-4 but serving GPT-3.5-turbo
• Token inflation — Reporting 2-3x more tokens than actually consumed
• Hidden system prompts — Injecting instructions that make cheap models mimic expensive ones
• Data interception — Logging your prompts and responses through relay servers

How to Check Your API Key

With API-DNA, you can verify any API key in seconds — for free. Simply paste your key and our engine will:

1. Identify the provider — Determine if your key is for OpenAI, Anthropic, Google, or a relay
2. Detect the real model — Use behavioral fingerprinting to identify the actual model behind your endpoint
3. Audit token counts — Compare reported token usage against our independent estimate
4. Check for relay chains — Trace whether your requests pass through intermediary servers

Supported API Providers

API-DNA can check keys from all major providers and their resellers:

• OpenAI — GPT-4, GPT-4o, GPT-3.5-turbo (keys starting with sk-)
• Anthropic — Claude 3.5, Claude 3 Opus/Sonnet/Haiku (keys starting with sk-ant-)
• Google Gemini — Gemini Pro, Gemini Ultra (keys starting with AIza)
• Chinese providers — Zhipu (智谱), Moonshot, DeepSeek, Qwen
• OpenAI-compatible relays — Any endpoint using the OpenAI API format

What Makes API-DNA Different

Unlike simple key validators that only check if a key is valid, API-DNA performs deep behavioral analysis:

• Claimed vs Detected model comparison — See what the provider says vs what you actually get
• Token inflation detection — Quantify exactly how much your tokens are being inflated
• Infrastructure analysis — IP/ASN ownership, server headers, architecture fingerprinting
• No data retention — Your API key is used only for the scan and results are stored locally

Free API Key Checker — Try Now

Don't pay for fake models. Check your API key right now — it takes less than 30 seconds and it's completely free.