API Authentication Methods: A Practical Overview
Every non-public API has to answer the same question on every request: who (or what) is calling? “Authentication” is how it answers that. It’s easy to conflate with authorization — authentication confirms identity, authorization decides what that identity is allowed to do — but most API docs use “auth” loosely to cover both. This page is about the authentication side: the credential itself, and how it gets sent.
The Three Common Methods, at a Glance
| Method | Best for | Expires? |
|---|---|---|
| API Key | Identifying an app or project, not a specific user | Rarely, unless rotated manually |
| Bearer Token | A logged-in session or a token issued after some prior exchange | Usually, often short-lived |
| OAuth 2.0 | User consent, scoped access, or machine-to-machine auth between services you control | Access tokens expire; refresh tokens renew them |
They’re not mutually exclusive in practice — an OAuth 2.0 flow produces an access token that’s sent as a bearer token. The three pages linked above go deeper on each; this page is about choosing between them.
Choosing the Right Method
A few practical starting points:
- Building an internal tool or a personal project against a third-party API? Whatever that API supports — you rarely get a choice. Check if it wants the key in a header or a query parameter (see API Keys).
- Building your own API with no per-user permissions to manage, just “which app is calling”? An API key is simpler to implement and simpler for your users to get right than a full OAuth flow.
- Building your own API where users log in and you need to know exactly who’s making each request, with the ability to revoke access without changing a password? Bearer tokens issued at login, or full OAuth 2.0 if you also need third-party apps to request scoped access on a user’s behalf.
- Two backend services you control need to talk to each other, with no user involved? OAuth 2.0’s client credentials grant, or a plain API key if the extra token-expiry machinery isn’t worth it for an internal-only service.
Transport Security Matters More Than the Method
Whichever method you pick, none of it means anything without HTTPS. Every one of these credentials — API key, bearer token, OAuth access token — is just a string in a header. Sent over plain HTTP, any of them is trivial to intercept. The choice of auth method affects expiry, scoping, and who the credential identifies; it doesn’t substitute for transport encryption.
Testing Auth in HTTP Titan
HTTP Titan’s Auth tab supports all three methods directly on a request or an entire collection — Bearer Token, Basic Auth, API Key (with a header/query toggle), and OAuth 2.0 client credentials with a “Get New Access Token” button. Environment variables let the same request use different credentials across local, staging, and production without editing the request itself.