Title: Warning: Cannot modify header information
Last modified: May 27, 2017

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# Warning: Cannot modify header information

 *  Resolved [c](https://wordpress.org/support/users/igneous/)
 * (@igneous)
 * [8 years, 11 months ago](https://wordpress.org/support/topic/warning-cannot-modify-header-information-179/)
 * I’m getting these errors on my Jetpack page on my sites. I have multiple sites
   on the same server and domain, and they’re all doing it. I tried to update the
   plugin, I tried to update wordpress, I deleted jetpack manually and uploaded 
   manually, nothing changed the error. Any thoughts on how to fix this? Thanks
   
   Warning: Cannot modify header information – headers already sent by (output started
   at /home/asdf/public_html/wp-admin/includes/template.php:1995) in /home/igneous/
   public_html/wp-includes/rest-api.php on line 492
 * Warning: Cannot modify header information – headers already sent by (output started
   at /home/asdf/public_html/asdf/wp-admin/includes/template.php:1995) in /home/
   asdf/public_html/asdf/wp-includes/rest-api.php on line 492

Viewing 1 replies (of 1 total)

 *  Plugin Author [Jeremy Herve](https://wordpress.org/support/users/jeherve/)
 * (@jeherve)
 * Jetpack Mechanic 🚀
 * [8 years, 11 months ago](https://wordpress.org/support/topic/warning-cannot-modify-header-information-179/#post-9177052)
 * That’s a common issue I’m afraid, and something that’s most likely caused by 
   another plugin on your site. You can follow the instructions below to find the
   source of the problem:
    1. Install and activate [the Query Monitor plugin](https://wordpress.org/plugins/query-monitor/).
    2. Load the dashboard page and check that the error is still displayed.
    3. In Query Monitor, locate the `wp-includes/rest-api.php` call where the error
       appears.
    4. In the “Call Stack” section, check the different calls that are run. Below each
       call you should see the file making that call in grey.
    5. If one of the calls is made by another plugin or your theme, try deactivating
       that plugin or switching themes.
    6. If that solves the problem, you can send that call stack to the plugin or theme
       author to let them know.
 * I hope this helps!

Viewing 1 replies (of 1 total)

The topic ‘Warning: Cannot modify header information’ is closed to new replies.

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 * 1 reply
 * 2 participants
 * Last reply from: [Jeremy Herve](https://wordpress.org/support/users/jeherve/)
 * Last activity: [8 years, 11 months ago](https://wordpress.org/support/topic/warning-cannot-modify-header-information-179/#post-9177052)
 * Status: resolved