# REST Authentication

The Number Lookup API uses the standard HTTP `Authorization` header to pass authentication information to the Sinch servers. You can use [basic authentication](/docs/number-lookup-api-v2/api-reference/authentication/basic) or [OAuth](/docs/number-lookup-api-v2/api-reference/authentication/oauth).

Authentication method to use depends on your workflow.

- [OAuth authentication](/docs/number-lookup-api-v2/api-reference/authentication/oauth) (recommended)
- [basic authentication](/docs/number-lookup-api-v2/api-reference/authentication/basic) (for prototyping)