How to Resolve the ‘Cookies Are Blocked Due to Unexpected Output’

The ‘Cookies are blocked due to unexpected output’ error is a frequent problem encountered by WordPress users while troubleshooting their websites. This error can prevent you from logging in or accessing your WordPress admin panel, often leaving you stranded at critical moments.

Typically, this issue emerges after making small adjustments to your site, such as editing a theme or activating a plugin. Identifying the exact cause can be challenging and frustrating.

The good news? This error is entirely fixable.

In this article, we’ll outline the step-by-step process we use to diagnose and resolve this issue, helping you restore your website seamlessly and stress-free.

Cookies Are Blocked Due to Unexpected Output

What Happened to the Theme File Editor?

From our experience, the ‘Cookies Are Blocked Due to Unexpected Output’ error often occurs when a custom code snippet, a WordPress plugin, or a theme generates an output that disrupts the proper loading sequence of WordPress files.

WordPress operates by executing a predefined set of instructions behind the scenes to ensure your website functions smoothly. If this process is interrupted—whether by a code conflict or an unexpected output—WordPress may start to misbehave.

For example, this specific error arises when WordPress fails to set the login cookie, even though other parts of the code may have loaded correctly.

Cookies Are Blocked Due to Unexpected Output

Understanding the Causes of the ‘Cookies Are Blocked Due to Unexpected Output’ Error

Although seemingly minor, this error can create significant inconvenience. For instance, it can prevent you and other users from logging into your WordPress site, disrupting access when you need it most.

Below are the most common reasons for this error:

  • Extra Whitespace in PHP Files: Accidental spaces or blank lines in files like wp-config.php or plugin files can trigger this issue.
  • Plugin Conflicts: Some plugins may generate unexpected output that interferes with cookies.
  • Outdated WordPress Core, Plugins, or Themes: Older versions can cause compatibility issues, leading to errors.
  • Custom Code: Recent additions of custom code snippets might introduce errors or unexpected outputs.
  • Hosting Environment Issues: Rarely, server misconfigurations can lead to this error.

By understanding these common causes, you can better pinpoint the source of the problem. In the next section, we’ll walk you through step-by-step troubleshooting methods to resolve this error effectively.

How to Fix the ‘Cookies Are Blocked Due to Unexpected Output’ Error

Resolving the ‘Cookies are blocked due to unexpected output’ error might appear challenging, but it’s often simpler than expected.

This guide walks you through straightforward steps to identify and fix the issue. These methods are derived from common causes we’ve encountered while assisting others facing the same problem.

Whether it’s a minor typo in your code, a problematic plugin, or an outdated theme, the solution is within reach.

Let’s begin by addressing the most common cause of this error.

1. Check for Extra Whitespace in PHP Files

A frequent cause of the ‘Cookies are blocked due to unexpected output’ error is the presence of extra whitespace in WordPress PHP files. These spaces can occur before the opening <?php tag or after the closing ?> tag in PHP files. Even a single blank line can disrupt the functionality.

Steps to Fix:

  1. Access Your Website Files:
    Use an FTP client or the File Manager tool provided in your hosting control panel to access your website’s files.
  2. Locate the wp-config.php File:
    Navigate to your website’s root directory and find the wp-config.php file. This is a common location for extra whitespace issues.
  3. Remove Extra Whitespace:
    Open the wp-config.php file and carefully inspect it for blank lines or spaces before the <?php tag or after the closing ?> tag. Delete any extra whitespace.
  4. Save and Upload the File:
    Save your changes and upload the corrected file back to your server.
  5. Test Your Website:
    Visit your website to check if the error is resolved.
  6. Repeat for Other Files If Necessary:
    If the issue persists, repeat the above steps for other frequently edited files, such as the functions.php file in your theme, especially if you recently edited or updated it.

Note:

Manually checking and cleaning all PHP files is impractical due to the sheer number of files in a typical WordPress installation, including plugins and themes. If cleaning wp-config.php or other common files doesn’t resolve the issue, proceed to the next troubleshooting steps outlined in this guide.

2. Deactivate All Plugins Temporarily

A plugin conflict is another common reason for the ‘Cookies are blocked due to unexpected output’ error. Disabling all plugins temporarily allows you to identify whether a specific plugin is causing the issue.

Steps to Deactivate Plugins:

  1. Via WordPress Dashboard (If Accessible):

    • Navigate to Plugins » Installed Plugins.
    • Select all plugins using the checkbox at the top.
    • From the bulk actions dropdown, choose ‘Deactivate’, and click ‘Apply’.
    • Refresh the page or attempt to log in to check if the error is resolved.
  2. Using FTP (If the Dashboard is Inaccessible):

    • Connect to your website using an FTP client or the File Manager tool in your hosting control panel.
    • Navigate to the wp-content folder.
    • Locate the plugins folder, right-click on it, and choose ‘Rename’.
    • Rename the folder to something like plugins.deactivated.

WordPress will no longer recognize the folder, effectively deactivating all plugins automatically.

Testing for the Error:

  • If the error disappears after deactivating all plugins, it confirms that one of the plugins was causing the issue.

Identifying the Problematic Plugin:

  • Restore the original name of the plugins folder or reactivate plugins one by one through the dashboard.
  • After enabling each plugin, refresh the website to check if the error reappears.
  • Once the problematic plugin is identified, deactivate it permanently or contact its developer for assistance.

For more detailed instructions, refer to our tutorial on how to deactivate all WordPress plugins.

3. Switch to a Default WordPress Theme

Your WordPress theme may cause the ‘Cookies are blocked due to unexpected output’ error, especially if it contains outdated code or produces unexpected output due to customizations. Switching to a default WordPress theme can help identify whether your current theme is the source of the problem.

Steps to Switch to a Default Theme:

  1. Using the WordPress Admin Area (If Accessible):
    • Navigate to Appearance » Themes in the WordPress dashboard.
    • Check if a default theme, like Twenty Twenty-Five or Twenty Twenty-Four, is already installed.
    • If a default theme is installed, click ‘Activate’ to switch to it.
    • If not installed, click the ‘Add New Theme’ button at the top, search for a default theme, and install it.
    For detailed guidance, refer to our tutorial on how to install a WordPress theme.
  2. Using FTP (If the Admin Area is Inaccessible):
    • Connect to your website using an FTP client or the File Manager tool in your hosting account.
    • Navigate to the /wp-content/ directory and locate the themes folder.
    • Right-click the themes folder and select ‘Rename’, changing the name to something like themes-deactivated. This disables the current theme.
  3. Create a New Themes Folder:
    • In the /wp-content/ directory, use your FTP client’s ‘Create directory’ option to create a new folder named themes.
  4. Download and Upload a Default Theme:
    • Visit the WordPress.org Themes Directory and download a default theme such as Twenty Twenty-Five or Twenty Twenty-Four.
    • Extract the downloaded theme’s ZIP file on your computer.
    • Upload the extracted folder to the new themes directory on your server using your FTP client.
  5. Activate the Default Theme Automatically:
    Once the default theme is the only one in the themes folder, WordPress will automatically activate it.

After Switching the Theme:

  • Visit your website to see if the error is resolved.
  • If the error disappears, the issue lies with your previous theme. You can try:
    • Updating the theme to its latest version.
    • Fixing the theme’s code.
    • Contacting the theme developer for assistance.

Switching to a default theme helps isolate the issue and ensures that your website continues to function smoothly.

4. Debugging with WP_DEBUG Mode

If the error persists after trying previous steps, enabling the WordPress debugging mode (WP_DEBUG) can help you pinpoint the exact cause. This built-in feature logs errors and warnings, providing insights into unexpected outputs disrupting your website.

Steps to Enable WP_DEBUG Mode:

  1. Access Your WordPress Files:

    • Use an FTP client or the File Manager in your hosting control panel to access your website’s root directory.
  2. Edit the wp-config.php File:

    • Locate the wp-config.php file in the root folder of your WordPress installation.
    • Open the file for editing.
  3. Enable Debugging:

    • Find the line that says:

/* That’s all, stop editing! Happy publishing. */

define( ‘WP_DEBUG’, true );
define( ‘WP_DEBUG_LOG’, true );
define( ‘WP_DEBUG_DISPLAY’, false );

    • Explanation:
      • The first line enables the debug mode.
      • The second line creates a log file (debug.log) in the /wp-content/ folder to store error messages.
      • The third line hides errors from being displayed on your website, ensuring sensitive information isn’t exposed to visitors.
  • Save and Upload the File:

    • Save the changes to the wp-config.php file and upload it back to your server.
  • Review the Debug Log File:

    • Navigate to the /wp-content/ folder and locate the debug.log file.
    • Open the file to examine the errors and warnings recorded there.
  • Fix the Identified Issues:

    • Use the logged information to identify and resolve the source of the error. This could involve correcting code, updating plugins/themes, or addressing server misconfigurations.
  • Disable WP_DEBUG Mode:

    • Once you’ve resolved the issue, disable debugging by editing the wp-config.php file again. Set WP_DEBUG to false:

define( ‘WP_DEBUG’, false );

This prevents sensitive information from being exposed unnecessarily.

Helpful Tips:

  • WP_DEBUG mode is especially useful for advanced users or when collaborating with a developer or support team.
  • If you need more detailed steps, check out our guide on enabling WordPress debug mode for troubleshooting.

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