API authentication verifies the identity of a user, application, or service before granting access to protected API resources. Every request to a protected endpoint needs to present some form of trusted credential, like a password or access token, before the API returns data or performs an action.
The API authentication method you choose determines how you verify an identity and how much confidence you can place in it. While stronger controls reduce unauthorized access and credential misuse, they also introduce token management and maintenance work. Simpler methods are faster to implement, but they may not provide enough protection for sensitive data.
This guide covers different REST API authentication methods and how to choose the right approach for your workflow.
API authentication vs. authorization
Authentication verifies who or what is making an API request, while authorization decides what that identity is allowed to access or do.
For example, an access token may confirm a request came from a specific application, but the permissions attached to the token determine whether the application can only read customer records or also edit and delete them.
7 common API authentication methods
The right authentication method depends on who’s calling the API, where the trust boundary sits, and what a compromised credential can potentially expose.
In practice, you rarely implement every method from scratch.
n8n is a source-available, AI-native automation platform. It allows you to connect virtually any service to one another. When building agent-based systems or LLM-powered automations, n8n helps you securely manage API credentials:
- Store encrypted credentials without exposing them to AI agents, so there’s no risk of API keys being leaked in your automations
- Create MCP servers that interact with various services and connect them to your Coding Agent or ChatGPT. This way, you provide your system with a single API key without having to store multiple keys in plain text or upload them to external cloud platforms.
Now, let’s take a look at the top authentication methods in depth.
API keys
API keys work best when one application or service needs to identify itself to another, and no user is granting delegated access. The API issues a unique string, and the caller includes it in a request header or query parameter. They’re common for public APIs that use keys to identify callers and enforce usage limits.
This makes API keys easy to implement, but they’re often long-lived and provide broad access. If one leaks, anyone holding it may be able to impersonate the application until you rotate or revoke it.
Basic authentication
Basic authentication is appropriate for a trusted internal integration or an older API that expects a username and password. The call only needs to identify itself, and both systems operate within a relatively narrow trust boundary.
The client combines the username and password, Base64 encodes them, and sends the result in the “Authorization” header with every request. Base64 encoding doesn’t encrypt the credentials, so Basic Auth must always run over HTTPS. It’s straightforward to configure, but a stolen credential remains useful until you change it.
mTLS
For service-to-service integrations that need stronger assurance, mTLS provides cryptographic proof tied to the connection or request. It authenticates both the client and server using TLS certificates, but the added certificate management can increase operational overhead.
HMAC
HMAC, or hash-based message authentication code, signs individual API calls using a shared secret and requests data like a timestamp or payload. This helps the API detect any tampering and replay attacks, though HMAC needs shared-secret and replay protection to secure requests.
OAuth 2.0
OAuth 2.0 (or OAuth2) is a better fit for your workflow when a third-party application needs limited access to a user’s resource without receiving their password. It also supports service-to-service connections where an application acts on its own behalf.
With the authorization code flow, the user approves specific permissions before the application receives an access token. In this case, the client credentials flow removes the user from the process and issues a token directly to the trusted service.
JWT
A JSON Web Token (JWT) works well when an API needs a compact, signed token that carries information about a user or service. The token and issuer share a trust relationship through a secret or public-private key pair.
Keep in mind that JWT is a token format often layered with OAuth 2.0, not an authentication protocol. The caller may represent the user or service, but that doesn’t mean the JWT inherently delegates access.
A JWT contains the following claims:
- The issuer
- The intended audience
- Permissions
- Expiration time and date
The API can verify the signature without looking up a server-side session, making JWTs stateless and suited to scale across distributed systems. The tradeoff is that a valid token can be difficult to revoke before it expires.
OpenID Connect
OpenID is for cases where web apps use a user authentication API to verify identity to support a single sign-on (SSO), like “Sign in with Google.” The application trusts an external identity provider to authenticate the user instead of handling the user’s credentials itself.
OpenID Connect adds an identity layer to OAuth 2.0 and returns an ID token containing verified information about the user. That ID token tells the application who signed in, while a separate access token determines what an API will allow the application to do. This makes OpenID Connect useful for centralized login and SSO, but it isn’t a substitute for API authorization.
Best practices for API authentication and security
A secure authentication method can still fail due to reasons like poorly stored credentials or unvalidated tokens. These practices reduce those risks:
- Use HTTPS/TLS for every API request: TLS encrypts data traveling between the client and API, protecting passwords, API keys, and tokens from interception. Never send credentials over an unencrypted connection, even for internal services.
- Validate tokens on every request: Don’t assume a token’s validity because it worked previously. Check its signature, expiration time, issuer, intended audience, and required scopes each time the API receives it.
- Plan for token expiration, rotation, and revocation: Use short-lived access tokens wherever possible, and rotate long-lived API keys and client secrets on a defined schedule. You should be able to revoke a credential immediately if it leaks, an employee leaves, or an integration no longer needs access.
- Apply least-privilege scopes and permissions: Give each user, application, or service the minimum amount of access required for its task. Narrow permissions limit the damage a compromised credential can cause.
- Monitor and audit authentication activity: Record successful and failed authentication attempts, token issuance, credential changes, and revocations. Keep an eye out for unusual access patterns as repeated failures or requests from unexpected locations might indicate credential misuse.
How to choose the right API authentication method
The right choice for your workflow and integrations depends on how much trust exists between the systems, how sensitive the exposed resources are, and what could happen if a credential is compromised.
For example, a low-risk integration may only need reliable identification, while access to user data should have tighter permissions with shorter-lived credentials and easy revocation.
Choose a method your company can operate reliably. Stronger controls are only necessary if you constantly manage token refresh, credential rotation, and issues like authentication failures over time. From a practical perspective, the best authentication method is one that meets the integration’s security and lifecycle requirements without introducing complex upkeep.
How n8n handles API authentication
Once you choose an authentication method, n8n handles the setup around it. Every n8n workflow that connects to a protected external API must authenticate, but you don’t need to rebuild that logic every time.
You configure a credential once and reuse it wherever a workflow needs to connect to that service. This keeps secrets separate from the workflow itself and avoids copying API keys or tokens into individual nodes.
For OAuth 2.0 connections, n8n also manages the authorization flow and refreshes access tokens automatically, so workflows continue running after a token expires.
When there isn’t a dedicated n8n integration, you can achieve REST API authentication through the HTTP Request node using Basic Auth, API keys, OAuth 2.0, bearer tokens, or custom headers. n8n encrypts stored credentials, so you control how to share them across projects.
Put the right authentication method into practice with n8n
There isn’t a one-size-fits-all API authentication method that fits every situation. API keys or Basic Auth may be enough for a straightforward service-to-service connection, while OAuth 2.0 is better for applications that need delegated access with limited permissions. Start with the level of access your workflow needs and consider the controls you can maintain in the long run.
n8n provides reliable security without the complexity. This platform acts as an intermediary for AI agents or code agents that often lack secure storage for external service credentials, creating a risk of API key leaks. n8n lets you store encrypted credentials without exposure to AI agents, and create connected MCP servers with a single API key.