Title: Output Buffering Issues
Last modified: February 19, 2020

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# Output Buffering Issues

 *  [Henry](https://wordpress.org/support/users/henrybaum/)
 * (@henrybaum)
 * [6 years, 3 months ago](https://wordpress.org/support/topic/output-buffering-issues/)
 * Hi,
 * I keep getting this error for every link on the sidebar of the linked page – “
   Fatal error: Unknown: Cannot use output buffering in output buffering display
   handlers in Unknown on line 0.” I’ve seen it crop up on other pages on the site
   as well. Refreshing the page makes the error go away.
 * For some reason this problem doesn’t happen for logged-in users. Optimize for
   logged-in users is turned off.
 * I’ve tried to exclude cv.js with Minify excluded deselected, but it didn’t help.
   Currently using WP Rocket with their Minify HTML option turned on, and not Optimize
   HTML in AO.
 * TBH, I’m not even sure it’s an AO issue, but this error comes up a lot in relation
   to AO.
 * The page I need help with: _[[log in](https://login.wordpress.org/?redirect_to=https%3A%2F%2Fwordpress.org%2Fsupport%2Ftopic%2Foutput-buffering-issues%2F%3Foutput_format%3Dmd&locale=en_US)
   to see the link]_

Viewing 7 replies - 1 through 7 (of 7 total)

 *  Plugin Author [Optimizing Matters](https://wordpress.org/support/users/optimizingmatters/)
 * (@optimizingmatters)
 * [6 years, 3 months ago](https://wordpress.org/support/topic/output-buffering-issues/#post-12456244)
 * could be a conflict between Autoptimize and another plugin using the output buffer
   Henry, you could try recursively searching the entire `wp-content/plugins` folder
   for the `ob_` string and take it from there OR systematically disable plugins
   one at a time to try to find the culprit?
 *  Thread Starter [Henry](https://wordpress.org/support/users/henrybaum/)
 * (@henrybaum)
 * [6 years, 3 months ago](https://wordpress.org/support/topic/output-buffering-issues/#post-12456858)
 * Thanks – I think it’s All in One SEO. Turning off SEO for those pages has fixed
   the issue. Do you know about any conflicts?
 *  Plugin Author [Optimizing Matters](https://wordpress.org/support/users/optimizingmatters/)
 * (@optimizingmatters)
 * [6 years, 3 months ago](https://wordpress.org/support/topic/output-buffering-issues/#post-12457011)
 * hmmm … so do they have logic to replace the title somehow, could be that?
 *  Thread Starter [Henry](https://wordpress.org/support/users/henrybaum/)
 * (@henrybaum)
 * [6 years, 3 months ago](https://wordpress.org/support/topic/output-buffering-issues/#post-12457038)
 * Sorry, I spoke too soon. Still broken, but better somehow. Where is ob_start 
   normally found in plugins?
 *  Plugin Author [Optimizing Matters](https://wordpress.org/support/users/optimizingmatters/)
 * (@optimizingmatters)
 * [6 years, 3 months ago](https://wordpress.org/support/topic/output-buffering-issues/#post-12457074)
 * could be in any PHP-file really :-/
 *  [arnaudbroes](https://wordpress.org/support/users/arnaudbroes/)
 * (@arnaudbroes)
 * [6 years, 3 months ago](https://wordpress.org/support/topic/output-buffering-issues/#post-12457385)
 * AIOSEOP dev here. We use output buffering to rewrite the title tag. We plan on
   moving away from output buffering entirely in the future.
 *  Plugin Author [Optimizing Matters](https://wordpress.org/support/users/optimizingmatters/)
 * (@optimizingmatters)
 * [6 years, 2 months ago](https://wordpress.org/support/topic/output-buffering-issues/#post-12552342)
 * have you been able to get this working/ pinpoint it [@henrybaum](https://wordpress.org/support/users/henrybaum/)?

Viewing 7 replies - 1 through 7 (of 7 total)

The topic ‘Output Buffering Issues’ is closed to new replies.

 * ![](https://ps.w.org/autoptimize/assets/icon-256X256.png?rev=2211608)
 * [Autoptimize](https://wordpress.org/plugins/autoptimize/)
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 * 7 replies
 * 3 participants
 * Last reply from: [Optimizing Matters](https://wordpress.org/support/users/optimizingmatters/)
 * Last activity: [6 years, 2 months ago](https://wordpress.org/support/topic/output-buffering-issues/#post-12552342)
 * Status: not resolved