{"id":4858,"date":"2019-10-31T15:30:47","date_gmt":"2019-10-31T15:30:47","guid":{"rendered":"https:\/\/www.hostinger.com\/tutorials\/?p=4858"},"modified":"2026-03-10T10:12:45","modified_gmt":"2026-03-10T10:12:45","slug":"how-to-fix-cannot-modify-header-information-error-in-wordpress","status":"publish","type":"post","link":"\/uk\/tutorials\/how-to-fix-cannot-modify-header-information-error-in-wordpress\/","title":{"rendered":"How to fix the \u201ccannot modify header information \u2013 headers already sent by\u201d Error"},"content":{"rendered":"

The “Cannot modify header information” error in WordPress typically occurs when there is an attempt to modify HTTP headers after they have already been sent. This issue is relatively common and can affect the functionality of your plugins, themes, and the WordPress core.<\/p>

If you encounter this error message, it’s crucial to resolve it quickly to prevent any harm to your website’s performance.<\/p>

This WordPress guide will walk you through the troubleshooting steps to fix the “Cannot modify header information” error. First, let’s explore the potential causes.<\/p>

Download all in one WordPress cheat sheet<\/a><\/p>

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\n What Is the “Cannot Modify Header Information – Headers Already Sent By” Error?\n <\/p>\n <\/div>\n

The “Cannot modify header information” error happens when HTTP headers are changed after being sent, usually due to whitespace or output before or after PHP tags in files. If left unresolved, this common issue can disrupt the functionality of plugins, themes, and the WordPress core.<\/p><\/div>\n\n\n\n<\/p>

What Causes the “Cannot Modify Header Information – Headers Already Sent By” Error<\/h3>

In most cases, the “Cannot modify header information” error is caused by any output like misplaced text or extra whitespaces before the <?php<\/strong> opening tag or after the ?><\/strong> closing tag in PHP files.<\/p>

Conflicting code within plugins or themes and unexpected print <\/strong>or echo <\/strong>statements that generate output before headers are modified can also trigger this error message.<\/p>

How to Fix the “Cannot Modify Header Information – Headers Already Sent By” Error<\/h2>

You can fix this common WordPress error by modifying your website files with a File Manager <\/strong>or an FTP client like FileZilla<\/a>.<\/p>

We’ll show you how to resolve the “Cannot modify header information” error using Hostinger’s File Manager, which is available on all WordPress hosting<\/a> plans.<\/p>

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\n Important!<\/strong> Back up your WordPress website<\/a> to avoid data loss during troubleshooting.\n <\/p><\/div>\n\n\n\n<\/p>

1. Identify the Error Location<\/h3>

The “Cannot modify header information” error message usually contains information about the file and line number where the error occurs. Here’s an example of what it might look like:<\/p>

Warning: Cannot modify header information – headers already sent by (output started at \/public_html\/wp-content\/plugins\/plugin-name\/function.php:4) in \/public_html\/wp-includes\/pluggable.php on line 1300<\/pre>
From that, we know that the first output from the function.php<\/strong> file in line 4 causes the attempt to modify headers in the pluggable.php<\/strong> file in line 1300 to fail.<\/p>
To fix this issue, we need to troubleshoot the faulty function.php<\/strong> file.<\/p>
2. Edit the Faulty File<\/h3>
After identifying the error’s location, use Hostinger’s File Manager to check for and remove extra blank spaces from the faulty PHP file. Here’s how:<\/p>
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  1. Go to Files <\/strong>→ File Manager<\/strong> from hPanel, then access the files of your WordPress website.<\/li>\n<\/ol>
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