If Elementor shows a "Server Error." message when you save a page, or the WordPress editor says "Updating failed. The response is not a valid JSON response.", the most likely cause is a known bug in Elementor 4.3. It affects sites where Elementor's CSS Print Method is set to Internal Embedding. Changing that one setting fixes it, and it isn't a problem with your content or your hosting.
In most cases the save goes through, and the error appears afterwards, when the editor tries to read the server's reply. Reload the editor to check your changes are there before you redo any work.
How to tell if this is your issue
Your site runs Elementor 4.3.0, 4.3.1 or 4.3.2. Version 4.3.0 came out on September 22, 2026, and many sites updated to it automatically.
The Elementor message is just "Server Error." with no number. A message with a number, such as "Server Error (503)", is a different problem.
Only some pages are affected. Pages that pull in other Elementor content, such as templates, global widgets, loop grids, or add-on widgets, fail. Simpler pages save normally.
Deactivating other plugins doesn't help, and neither does restoring a backup.
In Elementor → Settings → Performance, CSS Print Method is set to Internal Embedding.
If you have WordPress debug logging turned on (see Debugging your site), each failed save also logs this warning:
PHP Warning: Cannot modify header information - headers already sent by (output started at .../wp-content/plugins/elementor/core/files/css/base.php:244)
How to fix it
This takes about two minutes. You'll need an administrator account in WordPress.
In your WordPress dashboard, go to Elementor → Settings and open the Performance tab.
Change CSS Print Method to External File.
Click Save Changes.
Go to Elementor → Tools. On the General tab, click Clear Files & Data. Elementor rebuilds its CSS files the next time each page is visited.
In the Wordify Console, open your site and click Clear Cache at the top of the page (see Using SmartCache).
Open the page in Elementor and save it again. It should save without an error.
External File is Elementor's default setting, and the one Elementor recommends for performance, so it's fine to leave it on.
Don't restore a backup for this
The CSS Print Method is saved in your site's database, so a backup brings back the same setting. Restoring one rolls back your recent content, and the error comes straight back.
What causes it
With Internal Embedding, Elementor adds each page's CSS directly to the page's HTML. A change in Elementor 4.3.0 means that when a save also renders other Elementor content, that CSS gets printed at the start of the save response. The editor expects a clean JSON reply, can't read it, and shows the error.
The bug is in Elementor itself, so it happens on any host. Elementor is tracking it in GitHub issue #37468. As of September 29, 2026 they're investigating, and versions 4.3.1 and 4.3.2 don't fix it.
Switching back to Internal Embedding
Only switch back if you chose Internal Embedding for a specific reason. Wait for an Elementor release that fixes issue #37468, update to it, then switch back and test a save on one of the pages that was failing.
Still seeing the error?
If saves still fail after switching to External File, or the message includes a number, start a chat with us. Tell us which page you were editing and paste the exact message, and we'll check your site's logs. We're available 24/7 and respond within an hour.