# API Keys vs Other Auth Methods

## The Authentication Landscape

No single authentication method is right for every situation. API keys, OAuth 2.0, JWTs, Basic Auth, and mTLS each solve different problems and carry different trade-offs. Understanding these distinctions is essential for choosing the right approach (or the right combination) for your API.

## Comparison Table

| | API Keys | OAuth 2.0 | JWTs | Basic Auth | mTLS |
| --- | --- | --- | --- | --- | --- |
| **Identifies** | Application / account | User (via delegated consent) | Bearer of the token | User (username + password) | Client certificate holder |
| **Complexity** | Low | High | Medium | Very low | High |
| **User delegation** | No | Yes | Depends on issuer | No | No |
| **Stateless validation** | No (requires lookup) | Depends on token format | Yes (signature check) | No (requires lookup) | Yes (certificate chain) |
| **Revocation** | Instant (delete from store) | Token + refresh revocation | Difficult (until expiry) | Change password | Revoke certificate (CRL/OCSP) |
| **Best suited for** | Server-to-server, metering | User-facing apps, third-party access | Microservices, short-lived auth | Internal tools, simple scripts | Zero-trust, infrastructure |

## API Keys vs OAuth 2.0

OAuth 2.0 is designed for **delegated authorization**: it lets a user grant a third-party application limited access to their resources without sharing their password. API keys, by contrast, identify the calling _application_ rather than the end user.

If you are building a public API where developers authenticate their own servers, API keys are simpler and more appropriate. If your API needs to act on behalf of individual users (e.g., "read this user's calendar"), OAuth 2.0 is the right tool. Many platforms use both: API keys for account-level access and billing, OAuth tokens for user-level operations.

**Key trade-off:** OAuth 2.0 adds significant implementation complexity (authorization servers, token endpoints, refresh flows, consent screens) in exchange for fine-grained, user-scoped access control.

## API Keys vs JWTs

A JSON Web Token (JWT) is a signed, self-contained token that carries claims (like user ID, roles, and expiration) directly in its payload. Because the server can validate a JWT by checking its signature without hitting a database, JWTs enable **stateless authentication**.

API keys require a [server-side lookup](/docs/implementation/validation-and-lookup) on every request, but this also means they can be **[revoked instantly](/docs/implementation/revocation)** by deleting the key from your data store. Revoking a JWT, on the other hand, is notoriously difficult. Since JWTs are validated locally, a compromised token remains valid until it expires unless you build additional infrastructure (token blocklists, short expiration windows, or forced re-issuance).

**Key trade-off:** JWTs offer lower validation latency and no shared state between services; API keys offer immediate revocability and simpler issuance.

## API Keys vs Basic Auth

Basic Authentication transmits a username and password encoded in Base64 with every request. It is the simplest possible authentication scheme and is built into the HTTP specification.

The problem is that Basic Auth sends credentials in a reversible encoding (not encryption) on every request, increasing exposure risk. It also ties authentication to a user's actual password, meaning a compromised Basic Auth header compromises the account itself. API keys, being independently generated secrets, can be rotated or revoked without changing a user's login credentials.

**Key trade-off:** Basic Auth requires zero setup but offers poor security posture for production APIs. API keys are nearly as simple to implement but provide much better operational control.

## API Keys vs mTLS

Mutual TLS (mTLS) authenticates both sides of a connection using X.509 certificates. The client presents a certificate during the TLS handshake, and the server validates it against a trusted certificate authority. This happens at the transport layer, before any HTTP request is even processed.

mTLS provides the strongest identity guarantees of any method on this list, but it comes with significant operational overhead: certificate provisioning, rotation, revocation lists, and managing a PKI (Public Key Infrastructure). It is most common in zero-trust architectures, service meshes, and infrastructure-level communication.

**Key trade-off:** mTLS provides cryptographically strong mutual authentication at the cost of substantial operational complexity. API keys are far simpler to manage but rely on the secrecy of a shared string.

## Combining Methods

In practice, many APIs layer multiple authentication methods. A common pattern is:

- **API keys** for application identification, rate limiting, and billing
- **OAuth 2.0 or JWTs** for user-level authorization on endpoints that act on behalf of a user
- **mTLS** for service-to-service communication within an internal network

The right choice depends on what you are protecting, who your consumers are, and how much operational complexity you are willing to take on. The page on [when to use API keys](/docs/introduction/when-to-use-api-keys) will help you determine when API keys alone are sufficient and when you should reach for something more.