> ## Documentation Index
> Fetch the complete documentation index at: https://docs.signupbear.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Authentication

> Authenticate API calls with a SignupBear bearer key.

Send the API key in the standard `Authorization` header:

```http theme={null}
Authorization: Bearer sg_test_replace_me
```

```bash theme={null}
curl https://signupbear.com/v1/check \
  --request POST \
  --header "Authorization: Bearer $SIGNUPBEAR_API_KEY" \
  --header "Content-Type: application/json" \
  --data '{"email":"low@signupbear.test"}'
```

Missing, malformed, revoked, or unknown keys return HTTP 401.

<Warning>
  API keys grant access to the account's checks and quota. Use them only from a
  trusted server environment.
</Warning>