Solution 1:
The error is triggered in WordPress core, but the actual cause is likely in your theme. One of your PHP files probably has extra spaces or line breaks before .
Check your theme files and remove any whitespace outside the PHP tags to resolve the issue.
Solution 2: Fixing “Cannot modify header information” Warning in WordPress
This warning usually occurs due to:
Extra spaces before, between, or after PHP opening/closing tags.
Unnecessary blank lines in a file.
Incorrect PHP file encoding.
Steps to fix:
Open your wp-config.php file in a code editor.
Remove all spaces or blank lines before .
This usually resolves the header-related warnings.