REST APIs probably sound familiar to anyone who has ever worked with online or mobile applications. They act as the backend messengers, enabling data transmission and reception between apps and servers. However, as with real-life discussions, not everyone should be able to hear or say everything. Here’s when authentication is useful.

In simple terms, authentication is the process by which a system determines your identity and, occasionally, your authority. There are various approaches of authenticating in the realm of REST APIs, each with unique use cases, advantages, and disadvantages.

We’ll go over the most popular REST API authentication techniques in this blog, explain how they operate, and assist you in determining which one would be best for your project.

Read More – REST API Design Principles for Developers

Is Authentication Necessary for REST APIs?

Suppose you are in charge of a coffee business. Things would get chaotic if it were possible for anyone to enter your business, go behind the counter, and brew their own coffee. If APIs are not properly safeguarded, that is precisely what might occur.

Authentication ensures that your API is only accessible by systems or individuals you trust. Additionally, it helps in monitoring user behavior, safeguarding private information, and avoiding abuse.

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Common REST API Authentication Methods

Let’s review the most popular authentication techniques in an understandable manner.

1. Authentication of API keys

How it works:

This can be similar to a secret passcode. You are given a special key when you sign up for a service. This key is included each time you send a request to the API, usually in the URL or request header.

Example:

GET /data HTTP/1.1
Host: api.example.com
Authorization: Api-Key abc123xyz

Advantages:

• Simple to put into practice
• Functions nicely for communication between servers

Disadvantages:

• Your key can be used as if it were theirs if it is stolen.
• only confirms that the key is there, not who is using it.

Ideal for: Simple apps, internal tools, or public APIs with limited security needs.

2. Basic Authentication

How it works:
Using this method, your username and password are sent in the header of each request, often encoded in Base64, which is a simple encoding and not encryption.

Example:

Authorization: Basic dXNlcm5hbWU6cGFzc3dvcmQ=

Advantages :

• Very easy to use and understand
  • Integrated inside HTTP, so no additional libraries are required

Disadvantages

• Not secure by itself; HTTPS is required to prevent password theft.
• On each request, the password is sent, even if it is encoded.
• No control over user sessions or token expiration

Ideal for: Rapid prototyping or testing settings; not advised for production use unless paired with HTTPS.

3. Bearer Token / OAuth 2.0

For modern applications, this approach is the most often used. It is more adaptable and safe than simple or API key approaches. The standard process is as follows:

1. The user enters their username and password to log in.
2. After confirming the login information, the server issues a token.
3. This token is saved by the client and sent in the header of every API request.

Example:

Authorization: Bearer eyJhbGciOiJIUzI1…

This token usually expires after some time. If so, a refresh token can be used by the client to obtain a new one without requiring the user to log in again.

Advantages:

• Safer than sending passwords
  • The ability of tokens to expire adds an additional degree of security.
• Extensively supported on many platforms

Disadvantages

• Implementation is a little more difficult.
• It might be challenging to manage tokens without the right configuration.

Ideal for: Third-party integrations, mobile apps, and web apps.

4. JSON Web Tokens, or JWT

How it Works:

JWT is a kind of token that is frequently utilized in OAuth2. Within the token itself, user data is stored in a digitally signed format. Thus, the server can depend on the contents of the token without having to search for it in a database.

Example : eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9… JWT has three parts:

• Header (defines algorithm)

• Payload (contains user data and claims)

• Signature (used to verify token integrity)

Advantages:

• Quick—no database query is required
  • Self-contained (able to retain important data, such as user roles)Fantastic for stateless APIs

Disadvantages

• A JWT can be used until it expires if it is stolen.
• Revocation is not possible (unless you are in charge of a token blacklist).

Ideal for: Scalable applications that require stateless authentication and performance considerations.

5. Session-Based Authentication

This is the traditional method for logging in to websites. The server creates and saves a session when a user signs in (typically in memory or a database). After then, the client receives a cookie, which they include with each request.

Advantages:

• Ideal for conventional web applications
• Tracking and canceling sessions is simple.

Cons:

• Not scalable for scattered or mobile systems
• Server-side session management is necessary.

Ideal for: Conventional browser-based web apps.

Related Post – 10 Common RESTful API Mistakes to Avoid

Example from the Real World: Logging in a Weather App

Suppose you create a weather app that allows users to bookmark their preferred spots. Nobody should have access to another person’s data.

1. Using their email address and password, a user logs in.
2. After authenticating them, your server returns a JWT token.
3. The token is saved by the app and is part of each request:
4. Only that user’s data is returned when your server has verified the token.
5. The user doesn’t have to log in each time thanks to this quick and safe flow.

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Conclusion

Authentication is a trust system, not merely a technical necessity. It is your responsibility to ensure that only the appropriate individuals enter your application and that they are only performing their assigned tasks.

Understanding your app’s requirements is crucial, regardless of whether you choose JWT for performance, OAuth for power and security, or API keys for simplicity.

Additionally, when handling sensitive data or user credentials, always—always—use HTTPS. Sending your authentication mechanism across an unencrypted connection is like locking your door and leaving the key under the mat, regardless of how secure it is.