API key
A fixed secret string that identifies an app or partner calling an API, usually sent in a header.
Definition
API keys identify applications rather than individual users, for example a restaurant's ordering system that updates its menu. Testers check that missing, wrong and revoked keys are rejected with 401, that one partner's key can't touch another partner's data, and that keys never appear in URLs, responses or logs.
In practice
A request with "x-api-key: test_pk_..." updates Partner 42's menu; the same request with Partner 43's key returns 403.
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Lessons that use this term.