Have you ever come across a “401 Unauthorized Error Access” when trying to access a website or web application? Understanding what this error message means and how to fix it is essential for any web developer.

In this article, we will discuss the basics of HTTP 401 Errors, and give an overview of some best practices for troubleshooting them.

• The error 401 belongs to the family of 4XX codes which mean that there is a problem with the request.
• The 401 status code appears when the client can’t be identified by the server.
• Generally this message is simply due to an incorrect URL, password or an expired session.
• Clearing the cache and flushing the DNS on your device can solve the problem.

What does the 401 error code mean?

A 401 error code is an HTTP status code that indicates that the client making the request (e.g. a web browser) is not authorized to reach the requested resource on the server. 

The 401 status code means that the client failed to provide valid identification credentials for the requested resource.

Where the error 404 is related to the server resource, error 401 is about the user.

For example: When a user tries to reach a page or resource that requires authentification, such as a protected webpage or a restricted API endpoint, the server will typically respond with a 401 error code if the user has not provided valid connection information.

The server may also include a WWW-Authenticate header in the response, which indicates the type of certification required to reach the resource.

When the 401 Unauthorized response status code is received by a web application, it means that the client request hasn’t been completed because it lacks valid authentification credentials for the requested resource.

In other words, the server has determined that there isn’t a valid username or password provided in order to access the requested resource.

Typically, this error occurs when an incorrect username and/or password are entered, but can also happen for other reasons…

Why do I get a 401 error?

There are a variety of reasons why a 401 error occurs. Common causes include:

• Incorrectly entered usernames and passwords.
• Expired session tokens.
• Error in the URL (for example if you type Guugle.com instead of Google.com)
• A WordPress security plugin failure
• Unauthorized access attempts to restricted resources.
• IP address filters that prevent certain users from accessing specific content.
• Failed authorization checks, such as an incorrect authentication token.

How can I fix the 401 error as a visitor?

Fortunately, you can troubleshoot 401 error status by:

• Checking your request for proper authentification credentials.
• Verifying that the username and password are correct.
• Checking if there is an IP address filter in place, and make sure you’re connecting from a valid IP address.
• Ensuring that your API key is valid and has not expired.
• Clearing your Domain Name System.
• Clearing your browser’s cache & cookies.
• Verifying if the server is experiencing issues and try again later.

But let’s see each of these points in detail.

Check your request for proper authentication credentials

In order to reach a resource, you will need to authenticate with the server. This could mean:

• providing valid username and password credentials,
• an API key that is active,
• or some other form of authentication.

Make sure you’re sending the correct information in your requests in order to proceed.

Verify that the username and password are correct

If you have entered incorrect login data, then 401 status code will occur when trying to reach a protected resource. Verify that the username and password are spelled correctly, as even small typos can cause 401 status.

Verify if there is an IP address filter in place

Certain websites might limit which user IP addresses are allowed to reach the site. If your IP address is not on the approved list, then a 401 error message will be displayed when trying to reach the resource.

Ensure that your API key is valid and has not expired

API keys often have expiration dates associated with them, and 401 Error can occur if an expired key is used. Make sure the API key being sent in your request is still valid and hasn’t expired yet.

Flush your DNS

A 401 Error could be caused by DNS issues. Clearing the cache and flushing your DNS can help resolve this type of error.

To flush your DNS you just have to:

1. Open the Command Prompt on Windows or Terminal on Mac.
2. Type the command “ipconfig /flushdns” (without quotes) and hit Enter.
3. Wait for the command to execute and for the message “Successfully flushed the DNS Resolver Cache” to appear.
4. Close the Command Prompt or Terminal.

On mobile devices, the process may vary slightly depending on the operating system. In general, you may need to go to the network settings and look for an option to flush the cache.

Clear your browser’s cache and cookies

Your device (smartphone, computer, laptop…) stores a lot of data as cache & cookies. These data can cause issues with authentification, so try clearing your browser’s cache and cookies and then try again.

To do so you have to:

Here are the general steps for clearing your cache and cookies in most web browsers:

1. Open your web browser (Google Chrome, Mozilla Firefox, etc…).
2. Open the browser’s settings or options menu. This is usually accessed via a button with three dots or lines in the top-right or top-left corner of the window.
3. Click on “Settings” or “Options.”
4. Find the section for “Privacy and security.”
5. Click on “Clear browsing data” or “Clear browsing history.”
6. Choose the time range you want to clear (e.g. “All time” to flush everything).
7. Tick the boxes for “Cookies and other site data” and “Cached images and files.”
8. Click on “Clear data” or “Clear browsing data.”

Verify if the server is experiencing issues and try again later

401 errors can be caused by server issues or overloads. In such cases, wait a few minutes before attempting to connect again – sometimes this can resolve the 401 Unauthorized Access Error.

How can I fix the 401 error on my website?

If you are the administrator of a website and 401 Errors are occurring, then you can troubleshoot the problem by:

• Checking your server logs,
• Verifying the user’s login authorizations,
• Checking your website’s authentication settings,
• Checking for issues with you access control system,
• Testing the resource from a different location,
• Updating your access control rules,

Check your server logs

Checking your server logs is a good way to see if there are any errors or issues related to authentication or access control. You can also look for any failed login attempts or identification errors.

Verify the user’s login authorizations

If the error is related to a specific user or group of users, verify their authentication credentials to ensure that they have the correct username and password. You may also want to verify if the user’s account has been locked or suspended.

If the error persists, you can disable password protection for a short time to see if the login ID is causing the problem.

Check your website’s authentication settings

Make sure that your website’s authentification settings are configured correctly. Verify that users have the necessary permissions to access the requested resource and that the resource is protected by the appropriate level of access control.

Use the WWW-Authenticate header response

If you’re still experiencing a 401 error after trying the previous solutions, it may be caused by a server-side problem. To resolve this, you can look for the WWW-Authenticate header response to find out what type of authentication is required for access to be granted.

Check for issues with your access control system

If you are using an access control system, check for issues with the system. Verify that the system is configured correctly, and that it is up-to-date.

Deactivate your security plugins on WordPress

As we saw earlier, a plugin can cause a 401 error. If you are facing this kind of error try to disable your wordpress plugins to try to solve it. 

Test the resource from a different location

Test the resource from a different location to see if the issue is related to the user’s location or network. If the resource is accessible from other locations, the error may be related to the user’s network.

Update your access control rules

If you find that the issue is related to access control rules, update the rules to ensure that users have the appropriate level of access.

By taking these steps, you can identify and resolve the cause of the 401 Unauthorized Error code on your website. If you are still unable to resolve the issue, you may need to contact your website hosting provider or IT department for assistance.

401 Error in a nutshell…

Web developers should always be prepared for HTTP 401 Error. It is important to know how to recognize, diagnose and fix them.

By following the best practices outlined in this article, you can ensure that your web applications are running smoothly and securely. If you still have questions, don’t hesitate to reach out to a qualified professional for help.

• 401 Error message appears when the server denies access to the client.
• It means that your authentication to reach the website has failed.
• It can simply be due to a typo mistake in an username or a password.
• The easiest way to fix it is generally to correct the typo mistake.
• Clearing your browser’s from cache & cookies can also solve the issue.
• The error also can be caused by a WordPress plugin.

HTTP 401 Unauthorized Error: Comprehensive Guide

The HTTP 401 Unauthorized Error is a common client-side error indicating that authentication is required to access the requested resource. This guide will explain its causes, how to diagnose it, ways to fix it, and tips to prevent it in the future.

What is an HTTP 401 Unauthorized Error?

The HTTP 401 status code means that the client (e.g., browser or API client) has not provided valid authentication credentials to access a protected resource. This error is distinct from HTTP 403 Forbidden, which denies access even with valid credentials.

Common Causes of the HTTP 401 Error

• Invalid or Missing Credentials: The most common cause is failing to provide valid login details, such as a username and password, API key, or token.
• Session Expiration: Tokens or cookies used for authentication may have expired.
• Incorrect API Configuration: Misconfigured headers, incorrect endpoint usage, or expired API keys can trigger this error.
• Server-side Misconfiguration: Issues in the server authentication setup, such as incorrect .htaccess rules or misconfigured authentication modules.
• Security Plugins or Firewalls: CMS security plugins or firewalls may unintentionally block legitimate requests.

How to Diagnose the HTTP 401 Error

1. Check Credentials: Ensure that the username, password, API token, or other credentials being sent are correct.
2. Review Server Logs: Analyze server logs to identify patterns or errors related to authentication.
3. Test Different Accounts: Verify whether the issue is user-specific by testing with different accounts.
4. Inspect HTTP Headers: Use browser developer tools or tools like Postman to inspect headers and verify that authentication details are correctly passed.
5. Disable Plugins Temporarily: For websites using CMS platforms, deactivate security plugins to rule out interference.

How to Fix the HTTP 401 Unauthorized Error

1. Verify and Update Credentials:
   • Ensure the username and password are accurate for website logins.
   • For APIs, double-check the API key, token, or client credentials.
   • If tokens are expired, regenerate them and retry.
2. Set Proper Authentication Headers:

   Ensure the HTTP request includes the correct Authorization header. Examples:

   // Example for Bearer Token
   Authorization: Bearer YOUR_ACCESS_TOKEN
   
   // Example for Basic Auth
   Authorization: Basic BASE64_ENCODED_USERNAME_PASSWORD

3. Clear Cache and Cookies: Remove cached credentials and session data to avoid conflicts.
4. Verify URL and Endpoint: Ensure the URL used is valid and points to an accessible resource.
5. Fix Server Configuration:

   If you have access to the server, check for errors in:

   • .htaccess files
   • Authentication modules in Apache or NGINX
   • OAuth, JWT, or token-based setups
6. Inspect Plugin Settings: If the issue arises on platforms like WordPress, deactivate security plugins and reconfigure as needed.

How to Prevent HTTP 401 Errors

Follow these best practices to minimize the occurrence of HTTP 401 errors:

• Implement Clear Authentication Protocols: Ensure users and developers understand how to provide authentication credentials.
• Use HTTPS: Always enforce secure connections to protect credentials and prevent unauthorized access.
• Manage Session Expiration: Notify users when a session is about to expire and provide a smooth reauthentication process.
• Test Configurations Regularly: Perform routine tests on server and application configurations to identify and resolve authentication issues proactively.
• Monitor Logs: Use tools to monitor authentication logs for signs of recurring 401 errors and address root causes.

Example: HTTP 401 Request and Response

Here is an example of a typical request-response cycle when a 401 error occurs:

// Client Request
GET /protected-resource HTTP/1.1
Host: example.com

// Server Response
HTTP/1.1 401 Unauthorized
WWW-Authenticate: Basic realm="Access to the resource"

Understanding Related Errors

• HTTP 403 Forbidden: The client is authenticated but lacks the necessary permissions to access the resource.
• HTTP 404 Not Found: The requested resource does not exist on the server.
• HTTP 400 Bad Request: The server cannot process the request due to malformed syntax.

By understanding the causes and implementing the solutions described above, you can effectively handle and prevent HTTP 401 errors, ensuring a smoother user experience and improved application reliability.

See Also

HTTP error 400: how to fix it?