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Every Pro API v2 endpoint requires an API key. The Public API needs no authentication.

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Getting an API key

You can obtain your personal API key in your account settings on leakcheck.io. Keys are at least 40 characters long.

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Passing the key

There are two ways to authenticate a request:
  1. Header (recommended) — send the key in the X-API-Key header:
Accept: application/json
X-API-Key: 8cb2237d0679ca88db6464eac60da96345513964
  1. Query parameter — pass it as ?key=:
curl "https://leakcheck.io/api/v2/query/example@example.com?key=$LEAKCHECK_APIKEY"
Prefer the header: query strings tend to end up in access logs, proxies and browser history, so ?key= is best kept for quick tests and environments where setting headers is inconvenient.
curl "https://leakcheck.io/api/v2/query/example@example.com" \
  -H "Accept: application/json" \
  -H "X-API-Key: $LEAKCHECK_APIKEY"
Keep the key out of your source code — read it from an environment variable (the official Python wrapper picks up LEAKCHECK_APIKEY automatically).
Requests without the header are rejected with 401 Missing X-API-Key, and requests with a wrong key with 400 Invalid X-API-Key — see Errors for the full list.