API authentication is a security process that verifies the identity of a user, application, or service requesting an API. It answers “who is making this request?” before protected data or functions are available. Authentication is separate from authorization, which decides what an authenticated identity may do.
API authentication
What Is API Authentication?
API authentication verifies the identity of a user, application, or service requesting an API. It answers who is making the request before protected software data or functions are available. Authorization is separate, it decides what that verified identity can do.
How API Authentication Works
Authentication usually happens before an API returns a protected response.
- The client receives a credential, such as a key or token.
- It sends the credential over HTTPS.
- The API or gateway validates it and identifies the caller.
- Authorization checks permissions, then the API allows or denies the request.
Common API Authentication Methods
Choose a method that fits the caller and sensitivity of the data.
| Method | Best fit | Caution |
|---|---|---|
| API key | Server-to-server access | Rotate and restrict it. |
| HTTP Basic | Legacy systems | Use HTTPS only. |
| Bearer token | Session access | Possession grants access. |
| JWT | Stateless APIs | Validate signature and expiry. |
| OAuth 2.0 and OIDC | User delegation and login | Use narrow scopes. |
| Client certificate | High-trust services | Manage certificates carefully. |
Authentication vs. Authorization in APIs
Authentication proves an app is the customer portal. Authorization may then give it read-only access to one customer record. Failed or missing credentials commonly produce 401, while valid credentials without permission commonly produce 403.
API Security Best Practices
Secure credentials throughout their lifecycle.
- Use HTTPS and never place secrets in source code or URLs.
- Use short-lived tokens, rotation, revocation, and least-privilege scopes.
- Rate-limit requests, log access, and test denied-access paths.
API Authentication in Emergent
Apps built with Emergent may connect to third-party services, so secure credentials and permission checks matter. See authentication, REST APIs, and this tutorial for building with the Gmail API. Build secure API integrations with Emergent.
Frequently Asked Questions
Your Questions, Answered
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What are the different types of API authentication?
Common types include API keys, HTTP Basic authentication, bearer tokens, JWTs, OAuth 2.0 with OpenID Connect, and client certificates.
What is the difference between authentication and authorization in an API?
Authentication verifies who is calling. Authorization determines which endpoints, records, or actions that caller may use.
How does API key authentication work?
The client sends an issued key, usually in a request header. The API validates the key and applies its assigned restrictions.
What is the most commonly used API authentication method?
API keys are common for simple service integrations. OAuth 2.0 is widely used when an app needs delegated user access.
Which API authentication method is least secure?
HTTP Basic authentication is risky when used without HTTPS because credentials can be exposed. Query-string API keys are also unsafe because URLs may be logged.
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