---
title: "Building API Endpoints"
description: "Building API endpoints and reverse proxies allows you to extend your application's capabilities by creating custom server-side routes and connecting your frontend seamlessly to external services. A..."
last_updated: "2026-10-12T06:40:49.103345+00:00"
canonical_url: "https://www.doc0.dev/docs/8f4009b0-65bd-4480-9b00-e201f0914bb3/guide/how-to-guides/building-api-endpoints"
---

## Overview

### Understanding Custom Endpoints and Reverse Proxies
Building API endpoints and reverse proxies allows you to extend your application's capabilities by creating custom server-side routes and connecting your frontend seamlessly to external services. API endpoints let you write custom backend logic to handle requests, process data, and return responses. A reverse proxy, on the other hand, acts as an intermediary that forwards incoming requests from your application to other servers or microservices, shielding your clients from directly addressing those external services.

```mermaid
flowchart TD
    A[Client Request] --> B{Request Type}
    B -->|Custom Logic| C[Build API Endpoint]
    B -->|External Service| D[Configure Reverse Proxy]
    C --> E[Return Response]
    D --> E
```

### Key Concepts
Before configuring your routes, it helps to understand the main components involved in managing server traffic:
* **API Endpoint:** A specific URL path on your server designed to receive requests, perform an action, and send back data.
* **Reverse Proxy:** A rule that automatically redirects incoming traffic from one path in your app to an entirely different web address or server.
* **Request and Response:** The incoming data sent by a user or client, and the resulting data sent back by your server.

> [!NOTE]
> Custom API endpoints run directly on your application's built-in server, meaning you do not need to set up a separate backend server just to handle lightweight tasks.

## Creating a Custom API Endpoint

### Writing Your First Endpoint
Writing a custom API endpoint allows you to handle incoming requests with your own tailored server-side logic. 

### 1. Choose Your Route Path
Determine the URL address where your endpoint will live (for example, `/api/hello` or `/api/submit-form`). Keep your paths descriptive and consistent.

### 2. Define the Request Method
Decide how clients will communicate with your endpoint. The most common methods are:
* **GET:** Used to retrieve data from the server.
* **POST:** Used to send new data to the server.
* **PUT / PATCH:** Used to update existing data.
* **DELETE:** Used to remove data.

### 3. Write Your Endpoint Logic
Create your endpoint handler to process incoming information and send a response back. Here is a simple example of a custom API endpoint that returns a greeting message:

```javascript
// Example of a basic API endpoint
export default async function handler(request, response) {
  const userName = request.query.name || 'Guest';
  
  response.status(200).json({
    message: `Hello, ${userName}! Welcome to our API.`
  });
}
```

> [!TIP]
> Always validate incoming data before processing it to prevent unexpected errors or security vulnerabilities in your application.

## Configuring a Reverse Proxy

### Setting Up Proxy Rules
A reverse proxy lets you route traffic coming into a specific path of your application directly to an external URL. This is especially useful for hiding internal service URLs, bypassing browser security restrictions, or integrating with third-party tools.

### 1. Identify Source and Destination
Determine the local path users will visit and the target URL where the request should actually go.

### 2. Set Up the Proxy Rule
Map your local path to the target server configuration. 

| Option | Description | Example |
| :--- | :--- | :--- |
| **Source Path** | The local URL pattern within your app | `/external-api/*` |
| **Destination URL** | The external server address to forward traffic to | `https://api.example.com/v1/*` |
| **Rewrite Rules** | Optional adjustments to paths during forwarding | Strip prefix before sending |

> [!WARNING]
> Be careful when proxying authentication headers. Ensure you only forward necessary authorization tokens to trusted third-party servers to protect sensitive user credentials.

## Troubleshooting and Best Practices

When building endpoints and proxies, keep these helpful tips and potential pitfalls in mind:

> [!IMPORTANT]
> If your frontend application attempts to fetch data from an external domain that does not allow cross-origin requests, use a reverse proxy to route the request through your own server domain and avoid browser blocks.

* **Test with Small Payloads:** Always test your API endpoints with simple data structures using a tool like a web browser or a command-line HTTP client before connecting your user interface.
* **Handle Errors Gracefully:** Ensure your endpoints return meaningful error messages and correct status codes (such as `404` for not found or `500` for server issues) when something goes wrong.
* **Avoid Infinite Loops:** When configuring a reverse proxy, make sure the destination URL does not point back to your own application's source path, which creates an endless routing loop.

## Related

- [Data Fetching and Mutation](https://www.doc0.dev/docs/8f4009b0-65bd-4480-9b00-e201f0914bb3/guide/core-features/data-fetching-and-mutation)


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