What is “401 Error Unauthorized Access” and How to Fix it?

Seen a “401 Unauthorized” or “Access Denied” message when visiting a website?

This error means your browser couldn’t prove you have permission to view a page.

The good news: it’s easy to fix. This guide explains what causes the 401 error and walks you through the steps to resolve it quickly.

Let’s get started!

Understanding the 401 Unauthorized Error

When you browse the internet, your web browser and the website’s server exchange messages to deliver the content you want to see. Most of the time, these exchanges are successful, and you never see any error codes. However, if you don’t have the necessary permissions to access a web page, you will see the 401 Unauthorized Error.

A 401 error happens when the server can’t verify your identity. In most cases, your login credentials are missing, invalid, or expired.

You might see this error displayed in a few different ways, but they all mean the same thing:

• “401 Authorization Required”
• “HTTP 401 Error – Unauthorized”
• “Access Denied”

This is a client-side error, meaning the problem is caused by the browser sending either incorrect or incomplete credentials to the server.

401 vs. 403 Errors – What’s the Difference?

The 401 and 403 errors look similar but mean different things:

Suggested read: How to Fix a 502 Bad Gateway Error

Common Reasons for a 401 Error

Once you understand what causes a 401 error, fixing it is simple. Follow these steps to resolve the issue and regain access.

1. Incorrect Login Details

Let’s start with the most obvious and common cause: a simple typo. You might have accidentally misspelled your username or entered the wrong password. Check for common mistakes like having Caps Lock on or mixing up similar characters like the number ‘0’ and the letter ‘O.

2. Outdated Browser Cache and Cookies

All modern browsers store bits of information from websites you visit in a local storage area called the browser cache. It also saves small files called browser cookies that remember your login status, site preferences, and other session data.

Storing this information locally is great for website performance, but it can sometimes cause a 401 error. If your browser’s cache or cookies become corrupted or outdated, your browser might send an old, invalid login token to the server. The server, seeing these incorrect credentials, denies you access and returns a 401 error.

3. An Incorrect URL or an Outdated Link

Sometimes the problem is as simple as a mistake in the web address. You may have typed the incorrect URL or clicked on an old bookmark that points to a page that no longer exists or has been moved behind a login wall. Certain pages on a website are meant to be private and require authentication. If you try to access one directly without being logged in, the server will correctly block you with a 401 error. Always double-check that the URL is correct and that you’re trying to access a public page or are properly logged into a private area.

4. Plugin or Theme Incompatibility (For Website Owners)

Security or firewall plugins can sometimes block valid logins after an update or misconfiguration. Temporarily disabling them can help identify the issue. This is a common source of WordPress errors, and it is often triggered after a recent update to a plugin, a theme, or the WordPress core itself.

5. Firewall Issues

A firewall (either on the website’s server or even on your own network) can cause a 401 error. A Web Application Firewall (WAF) is designed to identify and block suspicious traffic. If it detects what it perceives as a threat from your IP address (perhaps due to multiple failed login attempts), it may block your access to prevent a potential attack, which would result in a 401 Unauthorized response.

How to Fix a 401 Error (Step-by-Step)

Now that you understand what the 401 error is and where it comes from, it’s time to troubleshoot 401 issues and get you back in. We’ll start with the simplest solutions and work our way up to more technical fixes. Follow these steps in order, as the problem is often resolved within the first few steps.

1. Double-Check the URL

This may sound overly simple, but an incorrect URL is a frequent cause of this error. Make sure you have typed the web address correctly. Pay close attention to ensure you haven’t accidentally tried to access a page that is restricted to administrators or logged-in users.

If you clicked on a link from an email or another website, it might be an outdated link that now points to a protected resource. Try navigating to the website’s main homepage and then finding the page you need from there.

2. Review Your Login Credentials

The most common problem is a simple mistake in your username or password. Before trying anything else, carefully re-enter your login details.

• Check for typos.
• Ensure your Caps Lock key isn’t on.
• If you’re still locked out and are not 100% sure of your password, the safest bet is to use the “Forgot Password?” or “Reset Password” link on the login page. This eliminates any guesswork.

3. Clear Your Browser’s Cache and Cookies

If the URL and your login details are correct, the next step is to check your browser’s stored data. Outdated or corrupted cache and cookies can cause your browser to send invalid authentication information to the server. Clearing the browser cache is a quick and easy way to fix 401 errors.

Here’s how to do it on popular browsers:

• In Chrome or Firefox, open Settings → Privacy → Clear browsing data.
  
• Select Cookies and Cached images/files, then confirm.
  
• Restart your browser and try again.

After clearing the data, close your browser completely, reopen it, and try logging in again.

4. Deactivate Your WordPress Plugins (For Website Owners)

If you are experiencing the 401 error on your own WordPress site after an update, then a plugin (especially a security or firewall plugin) may be causing this error. The easiest way to check this is to deactivate WordPress plugins.

• If you can access your dashboard: Navigate to Plugins > Installed Plugins. Select all plugins by checking the top box, and from the Bulk actions dropdown, choose Deactivate. If the error disappears, you know a plugin was the cause. Reactivate them one by one, checking the site after each activation, until the error returns. The last plugin you activated is the culprit.
• If you are locked out of your dashboard: You’ll need to use an FTP client or your hosting provider’s File Manager. Navigate to the wp-content folder and find the plugins folder. Rename it to something like plugins_old. This will deactivate all plugins. If you can now log in, rename the folder back to plugins and then follow the one-by-one reactivation process from your dashboard.

5. Check the HTTP Headers (For Advanced Users)

This is a more technical step. When a server sends a 401 response, it also includes additional headers. These headers contain data that specifies which authentication scheme the server requires (e.g., Basic, Bearer). You can view this header using your browser’s developer tools.

1. Open the page causing the 401 error.
2. Right-click anywhere on the page and select Inspect or Inspect Element.
3. Go to the Network tab.
4. Reload the page. You’ll see a list of network requests.
5. Find the request with a 401 status (it will be red). Click on it.
6. In the details pane, look for the Headers tab. This can give a developer clues about why the authentication is failing.

6. Contact the Website Administrator

If none of these steps work, contact the site administrator.

Include:

• The URL causing the error
• The time it occurred
• The steps you’ve already tried

This information will help them identify and resolve the issue much faster.

Wrapping Up: Fixing 401 Errors the Easy Way

In this post, we’ve seen that “401 error” is rarely a sign of a major problem. More often than not, it’s a simple miscommunication between your browser and the server, usually caused by a minor issue like a typo, an outdated browser cache, or a conflicting plugin.

Most 401 errors are easy to fix, often caused by old logins, cached data, or a simple typo.

But if you manage multiple sites, dealing with access issues, plugins, and performance can take up valuable time.

RunCloud helps you focus on your work while it handles the rest – from security to server management.

Start your free RunCloud trial today and spend less time troubleshooting.