Anthropic Claude API Key Tester
Enter your Anthropic API key to verify it is valid and that the Messages API is reachable. The test fires a single low-cost request directly from your browser to api.anthropic.com — your key is never sent to APIMaster.
API Connectivity Test
Quick reachability check for your AI API endpoint
This tool sends a single short request directly from your browser to the URL you provide. APIMaster.AI does not receive or store your API key. Use it to confirm billing, permissions, and network access before running full fingerprint detection.
Request configuration
Test result
No result yet. Fill in the form, confirm the notice above, then run a test.
Test with curl in your terminal
The command below mirrors the browser request. Replace <API_KEY> with your real key when running locally.
curl -sS 'https://api.anthropic.com/v1/messages' \
-X POST \
-H 'content-type: application/json' \
-H 'x-api-key: <API_KEY>' \
-H 'anthropic-version: 2023-06-01' \
-H 'anthropic-dangerous-direct-browser-access: true'
--data-binary '{
"model": "claude-opus-4-8",
"max_tokens": 64,
"messages": [
{
"role": "user",
"content": "just say hi, nothing else"
}
]
}'- Click Copy above.
- Open Terminal (macOS/Linux) or PowerShell (Windows).
- Paste the command and press Enter.
- Inspect HTTP status and JSON in the output.
Common issues
401 — Unauthorized
Invalid, expired, or malformed API key. Regenerate the key at your provider and paste without extra spaces.
403 — Forbidden
Account lacks permission, billing is blocked, or this API format is not enabled for your key.
429 — Rate limited
Too many requests. Wait and retry, or reduce concurrency.
CORS — CORS / Failed to fetch
Many providers block browser calls. Use the generated curl command instead.
FAQ
How do I test my API key?
Pick a format, enter base URL, API key, model, and a short prompt, confirm the notice, then click Run test.
Is my key safe on this page?
Yes. Requests go straight from your browser to your API URL. APIMaster servers are not in the path and we do not log your key.
What if the test fails?
Check HTTP status and the raw body. Typical causes: wrong key, wrong format, insufficient balance, model access denied, rate limits, or CORS in the browser.
Can I test multiple keys?
Yes. Replace the key and run again; each run is independent.
Why provide a terminal command?
Terminal curl bypasses browser CORS and matches how backend services call APIs.
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