Custom REST API Endpoints WordPress

The WordPress REST API allows you to interact with WordPress data using standard HTTP requests, making it possible to build dynamic and modern front-end experiences. Beyond the built-in endpoints for posts, pages, and users, WordPress also lets you create custom REST API routes. Custom endpoints are especially useful when you want to expose specific data or run custom logic for applications, JavaScript widgets, or external systems.

✅ Example: Register a Custom REST Endpoint

Add this to your theme’s functions.php or a custom plugin:

add_action('rest_api_init', function(){
  register_rest_route('training/v1', '/message', [
    'methods'  => 'GET',
    'callback' => function(){
      return ['message' => 'Hello from custom API'];
    },
    'permission_callback' => '__return_true'
  ]);
});

🧠 How It Works

Part	Meaning
`rest_api_init`	Action hook that runs when WordPress registers REST routes
`register_rest_route()`	Creates a custom API endpoint
`training/v1`	Namespace and version for your API
`/message`	Endpoint path
`methods => 'GET'`	HTTP method allowed (GET, POST, etc.)
`callback`	Function that returns the response
`permission_callback`	Controls who can access the endpoint

🌐 How to Access the Custom Endpoint

Visit this URL in your browser:

https://your-site.com/wp-json/training/v1/message

You’ll receive a JSON response:

{
  "message": "Hello from custom API"
}

📌 Key Takeaways

Concept	Explanation
Custom REST endpoints expand WordPress into an app platform	Useful for headless sites or JavaScript front-ends
`register_rest_route()` defines the endpoint path and behavior	Works inside `rest_api_init` hook
Endpoints return JSON	Easy to use in mobile apps and SPA frameworks
`permission_callback` controls security	Always validate access when needed

✅ What You Can Do Next

Return posts, metadata, or user details
Accept POST input and process forms via REST
Build React or Vue front-ends powered by WordPress
Create APIs for mobile apps or external clients