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Solving API requests that return 404 errors: The fog of the API road, how to avoid the 404 trap

Preface​

You sit in front of your computer, excitedly initiate an API request, expecting to get a response from the server. However, when you see that the response is not data, but a 404 error, at that moment, you may feel depressed, thinking: "What did I do wrong?"

404, which stands for "not found", usually means that the resource you requested does not exist. But don't worry, it's not the end of the world. As a developer, solving the problem of 404 errors is like deciphering a small puzzle in the code. As long as you find the right clues, the problem will be solved!

Objective of this article​

This article will detail how to identify and solve the reasons why API requests return 404 errors, and provide some practical solutions and code demonstrations to help you get out of the fog of 404.

What is a 404 error?​

404 error, commonly known as "resource not found", is a standard response code in the HTTP protocol. When a user requests a page or resource that does not exist on the server, the server returns this error. In simple terms, it tells you: The resource you requested is not found here.

For APIs, a 404 error means that the API endpoint (URL) you requested does not exist, the server cannot understand your request, or there is no corresponding resource at all. It may occur in development, production environment or testing, and will affect your application or front-end display.

Why does a 404 error occur?​

There are usually the following reasons why API requests return a 404 error:

1. URL error​

This is the most common reason. If you type the wrong URL address or misspell the path, the server will naturally not be able to find the corresponding resource.

Common errors:

  • Missing some parts of the URL (for example, an "s" is missing in /users/).

  • Missing the path part (for example, /user/ is spelled as /users/).

  • Wrong query parameters or path variables.

2. API endpoint does not exist​

Sometimes, the path or endpoint of an API does not exist at all. For example, you requested /api/v1/xyz, but there is no API resource /xyz on the server.

3. Version Issue​

APIs often have multiple versions, such as /api/v1/users and /api/v2/users. If you use the wrong version number, it will also cause a 404 error.

4. Resource was deleted or renamed​

If a resource in the API is deleted, renamed, or moved, the original path will no longer be valid, and a 404 error will be returned.

5. Permission Issue​

Although 401 (Unauthorized) or 403 (Forbidden) are usually returned, in some cases, the server may return a 404 error if a resource is accessed that you do not have permission to access. The server cannot confirm whether the resource exists because you do not have permission to access it.

How to fix 404 errors?​

When you encounter a 404 error, the following steps can help you solve the problem:

1. Double-check the API URL​

First, you need to check whether the requested URL is correct. The most error-prone part of an API request is the path, especially for URL paths that contain dynamic parameters. For example:

# Wrong API request URL
https://api.example.com/v1/usrs/12345

As you can see, usrs is misspelled, it should be users. Check the API documentation and make sure the requested path is spelled correctly.

Correct request:

https://api.example.com/v1/users/12345

2. Check if the API endpoint exists​

Make sure the API endpoint you requested actually exists on the server side. You can confirm whether the endpoint is valid by checking the API documentation or using an API testing tool such as Postman or Insomnia.

For example, if you request /api/v1/xyz, but there is no such endpoint on the server, you will get a 404 error.

3. Confirm the version number is correct​

APIs often update versions, and if the version number you request does not exist or has been deprecated, a 404 error may be returned. Check whether the correct API version is used. For example:

# Wrong request: using an unsupported API version
https://api.example.com/v2/users

If the version number is v2, which is no longer supported, a 404 error will be returned. You should check the latest documentation and use the correct version number.

4. Check whether the resource has been deleted or renamed​

Sometimes resources in an API are deleted, renamed, or moved, causing the original path to no longer be valid. If you were able to access a resource before, but now you get a 404 error, it may have been changed or deleted.

You can confirm with the API provider whether the resource still exists or whether there is a new path that can replace the original path.

5. Verify request permissions​

Make sure you have permission to access the API resource. If the API endpoint requires authentication or specific permissions, make sure you have correctly configured the authentication token (such as Bearer Token, API Key, etc.) and your user account has permission to access the resource.

Code demonstration: How to debug 404 errors​

Assume that you are developing a Node.js application and use Axios to initiate HTTP requests. Here is a common 404 error scenario:

Request code (may return 404)​

const axios = require('axios');

axios.get('https://api.example.com/v1/usrs/12345')
  .then(response => {
    console.log('User data:', response.data);
  })
  .catch(error => {
    if (error.response) {
      // The server responded with an error code
      if (error.response.status === 404) {
        console.log('Error 404: Resource not found. Please check the URL!');
      } else {
        console.log('Unexpected error:', error.response.status);
      }
    } else if (error.request) {
      // Request no response
      console.log('No response received. Check the server!');
    } else {
      // Other Errors
      console.log('Error during request setup:', error.message);
    }
  });

Solution: Check the URL and correct it​

Suppose we find that usrs is a typo and should be users, so we modify the code as follows:

axios.get('https://api.example.com/v1/users/12345')
  .then(response => {
    console.log('User data:', response.data);
  })
  .catch(error => {
    if (error.response) {
      if (error.response.status === 404) {
        console.log('Error 404: Resource not found. Please check the URL!');
      } else {
        console.log('Unexpected error:', error.response.status);
      }
    } else if (error.request) {
      console.log('No response received. Check the server!');
    } else {
      console.log('Error during request setup:', error.message);
    }
  });

In this example, we checked the URL and found an error, then fixed the path and the problem was solved.

Summary​

It’s not a big deal to encounter a 404 error when requesting an API. As long as you carefully check the following points, the problem can usually be solved:

  1. Check if the API URL is correct;

  2. Confirm that the API endpoint exists;

  3. Check if the API version number is correct;

  4. Verify if the resource has been deleted or renamed;

  5. Ensure that the request permissions are configured correctly.

Solving 404 errors is not difficult. As long as you follow the steps to check and fix, your API requests will return data smoothly and avoid those crazy error messages!

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