`API key is invalid`

Resend · GET /domains · HTTP 400 validation_error

Status: ✅ verified:server:prod · first seen 2026-10-31 · last confirmed 2026-10-31 · 1 confirmation from 1 vantage

A request whose Bearer API key is not a valid key returns HTTP 400 validation_error "API key is invalid", not a 401 (a missing key is 401 missing_api_key), in the flat {statusCode, name, message} body with WWW-Authenticate: Bearer.

What to do

Send header Authorization = the account setting bearer_api_key.

Example

What probe af:resend:probe:invalid-key sends (prod) and what it checks in the answer; apifacts-invalid-key is a deliberately wrong key.

GET https://api.resend.com/domains
Authorization: Bearer apifacts-invalid-key

Response (only what the probe asserts; other fields omitted):

HTTP 400
www-authenticate: <matches ^Bearer>

{
  "statusCode": 400,
  "name": "validation_error",
  "message": "API key is invalid"
}

In your code

When an SDK receives this response:

SDK	Raises	Check
Python `resend`	`resend.exceptions.ValidationError`	`e.code == 400` · `e.error_type == "validation_error"`
Node `resend`	returns `{ data: null, error }`	`error.statusCode === 400` · `error.name === "validation_error"`

Read from the SDK source: resend 2.50.1: resend/request.py Request.perform, resend/exceptions.py ERRORS; resend 6.37.0: dist/index.cjs Resend.fetchRequest.

Fix 1:

headers["Authorization"] = YOUR_BEARER_API_KEY

Dimensions

env: prod · plan: any · region: any · account_state: anonymous

Evidence

Probe af:resend:probe:invalid-key (declarative, source)

Observations: none from reporters yet.

Related errors

API key is invalid · GET /emails/{email_id} · HTTP 400 validation_error
Missing API Key · GET /domains · HTTP 401 missing_api_key

Machine access

Match signature (what check() matches): api key is invalid

curl -s https://apifacts.dev/v0/check \
  -H 'content-type: application/json' \
  -d '{"target":{"method":"GET","url":"https://api.resend.com/domains"},"error":{"status":400,"body_excerpt":"api key is invalid"}}'

YAML: facts/resend/invalid-api-key-400.yaml

Data: CC BY 4.0 · apifacts registry · This page is generated; edit the YAML, not the page.