Errors

Error format and names.

Errors use the Resend format, so the Resend SDKs show them as { data: null, error }:

{
  "name": "validation_error",
  "statusCode": 422,
  "message": "Invalid `subject`: Too small: expected string to have >=1 characters"
}

Some errors add details: the blocking items of the pre-send review, for example.

Name	Status	Meaning
`missing_api_key`	401	No `Authorization: Bearer` header.
`restricted_api_key`	401	The key's level does not allow this route (e.g. a `signups` key on `/contacts`).
`invalid_api_key`	403	Unknown or revoked key, or a Resend key (`re_…`).
`validation_error`	422	The body or a parameter is invalid; `message` names the field.
`invalid_parameter`	422	A path id or cursor is malformed or unknown.
`missing_required_field`	422	A required field is missing.
`presend_blocked`	422	The pre-send review found blocking items; they are in `details.items`.
`not_found`	404	No such resource in your workspace.
`invalid_state`	409	The resource is not in a state that allows this (e.g. pausing an issue that is not sending).
`under_review`	409	The issue is held for a quick content review by our team.
`conflict`	409	The resource already exists, or can never be changed (e.g. a bounce suppression).
`plan_limit_reached`	403	Your plan's limit is reached (subscribers, keys, images).
`workspace_suspended`	403	The workspace is suspended; contact support.
`rate_limit_exceeded`	429	Too many requests; see the `ratelimit-*` and `retry-after` headers.
`monthly_quota_exceeded`	429	The monthly email quota of your plan is used up.
`invalid_idempotency_key`	400	The Idempotency-Key must be 1–256 characters.
`concurrent_idempotent_requests`	409	The same Idempotency-Key is still being processed.
`invalid_idempotent_request`	409	The same Idempotency-Key was used with another body.
`payload_too_large`	413	The upload is over the size limit.
`unsupported_media_type`	415	The upload is not a PNG, JPEG, GIF or WebP image.
`application_error`	500	Unexpected error on our side; retry later.
`service_unavailable`	503	A dependency is temporarily unavailable; retry later.