Something broke after optimizing your WordPress site?

How do I find what an optimization plugin broke?

One setting at a time. Turn off the setting you suspect, clear the cache and open the page in a private window. If the problem is gone, that's the setting: turn it back on and fix the part it breaks with the steps below.

Before you change a setting

• You're logged in. Logged-in users always get the unoptimized page.
• A cache still has the old page. Cloudflare, a host cache or your browser. Use Clear cache in the admin bar; the overview lists the cache layers the plugin found.
• Another speed plugin is still on. Two plugins that both defer scripts or combine CSS break pages that neither breaks alone. Turn the other one off, and your host's optimization features too.

A menu, slider or form stopped working

That's JavaScript. Turn off Defer scripts and Move scripts to the end of the page to confirm. Then find the script that belongs to the broken part (the slider's file name usually says it) and give it a script rule:

• Do not optimize leaves that script exactly as it was.
• Load render blocking makes the page wait for it. Use it for a script that changes the layout before the first paint.

If it still breaks, turn on Safe mode. A script that has to run while the page loads, such as an ad with document.write or a script with data-no-optimize, then keeps every script before it in place. It optimizes less, so try the rule first.

A script your theme calls right away can also break when it loads late. Turn off Optimize analytics, pixels and chat widgets to confirm, and check your own list under Also optimize these scripts.

More on how the plugin handles scripts: JavaScript.

The layout or styling looks wrong

• Styling off or missing: turn off Smart CSS bundles to confirm. Then put the stylesheet's name under Leave these stylesheets alone. If you turned on Minify CSS (it's off by default), turn it off again when a stylesheet has invalid CSS.
• Layout broken in odd places: turn off Minify HTML. Invalid HTML can fall apart when the minifier removes whitespace.
• Stretched images: turn off Add missing width and height to confirm. Then add img { height: auto; } to your CSS (Extra CSS works) and turn it on again.
• Icons appear late or not at all: turn off Show icon fonts a moment later, or take that icon's class out of Icon selectors if you added it there.
• The footer looks wrong when you scroll to it: turn off Render the footer later.

LCP got worse with the plugin on

Check whether the LCP image is lazy loaded: in a private window, right-click it, Inspect, look for loading="lazy". On a kind of page nobody has visited yet, only the first few images are kept from lazy loading, so a hero further down waits for that first visit. Stay a few seconds on that page in Chrome, logged out, and it's set up for your screen size. Or set Your own LCP element under Images. Your theme or another plugin can also add loading="lazy" after this plugin: turn off lazy loading there. More on the LCP image: images.

Debug a page

Under Advanced, Debug a page fetches a page of your site and shows every step the plugin took on it, such as which scripts it delayed or left in place, and why. Use it to find the script or stylesheet that belongs to the broken part.

Skip WP Core Web Vitals for one URL or one browser

• One URL: Advanced, Don't optimize these URLs (parts separated by |). To skip only the cache: Never cache under Page cache, Fine-tuning.
• Your own browser: a cookie named cwv_no_plugin_for_you switches the plugin off completely for that browser, so you can compare the page with and without it.

No change after the update from 7.x

On the first request after the update the plugin moves your 7.x settings over, and it stays off until that's done. If that fails, administrators see a notice with the error. The plugin tries again after five minutes, or right away when you deactivate and activate it. If the notice stays, mail me the error.

Send me the page

Write down the page, what you see and which setting makes it go away, and send it to me.