infoWordPress Core•codePHPhourglass_bottomloading-issueinfoajaxsettingsserver_configurationmemorymemory_limit•labelCommon•warningModerate

Preview could not be loaded error

The preview pane fails to render when WordPress fails to retrieve the requested page.

Typical triggers include corrupted theme files, broken .htaccess rules, server‑level blocks, insufficient PHP memory, or mismatched permalink settings. When any of these conditions occur the AJAX call which loads the preview aborts, leaving a blank pane.

Symptoms

[dashicons-warning]

Blank preview pane

The editor shows an empty gray area where the page should appear.

[dashicons-admin-tools]

Error toast appears

A notification displays “Preview could not be loaded” with an HTTP status code.

[dashicons-admin-generic]

Console network failure

Network tab shows a failed request to admin‑ajax.php with status 403 or 500.

Common Causes

Corrupted .htaccess

Rewrite rules are missing or malformed, preventing the preview URL from resolving.

Insufficient PHP memory

Memory limit is too low, causing PHP to abort the preview request.

Server‑level block

ModSecurity or firewall rule blocks the AJAX request, returning 403.

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