How should an API return errors without leaking security-sensitive information?

Return safe API errors without leaking security details

Explains safe error responses for auth failures, validation failures, server errors, and sensitive resource access.

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I would return consistent, structured errors with safe messages. Validation errors can explain which submitted fields are invalid. Authentication failures should be generic enough to avoid revealing whether an account exists or why a token failed. Server errors should not return stack traces, SQL details, secrets, or internal exception messages.

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ProblemDetails, generic auth errors, validation detail, correlation ids, stack traces, resource existence, and logging.

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Why this question matters
Error responses are part of the security surface. They need to help legitimate clients without helping attackers map private data.
I would return consistent, structured errors with safe messages. Validation errors can explain which submitted fields are invalid. Authentication failures should be generic enough to avoid revealing whether an account exists or why a token failed. Server errors should not return stack traces, SQL details, secrets, or internal exception messages.
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I would include a correlation id in error responses so support can find the detailed server logs. For unauthorized resource access, the API should decide whether to return 403 or 404 based on whether revealing existence is acceptable. Public endpoints should be especially careful with account lookup, password reset, invitations, and private resource ids. The client gets enough information to recover, while sensitive detail stays in protected logs.

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Returning stack traces or raw exception messages.
Revealing whether an email exists during login or reset.
Using inconsistent 401, 403, and 404 behavior.
Logging bearer tokens or secrets inside error context.

How should an API return errors without leaking security-sensitive information?

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