API Versioning and Documentation

As APIs grow, their structure and behavior often change over time. API versioning helps developers introduce updates without breaking applications that already use older API versions.

One of the most common approaches is URL versioning.

Example:

/api/v1/users

When a new version is released, the API can use a different version path.

Example:

/api/v2/users

Another approach is header-based versioning, where the version is sent through request headers instead of the URL.

Versioning is important because changing endpoints or response formats without version control can break existing client applications.

Documenting APIs

Good API documentation helps developers understand:

• Available endpoints;
• Required request data;
• Response formats;
• Status codes;
• Authentication requirements.

Simple documentation can start with comments inside route handlers.

Example:

// GET /users/:id
// Returns a single user by ID
app.get('/users/:id', (req, res) => {
  res.send('User details');
});

For larger applications, developers often use tools based on the OpenAPI specification, such as Swagger, to generate structured API documentation automatically.

Well-documented APIs are easier to maintain, test, and integrate with other applications.