As experienced WordPress developers, we've helped countless site owners customize their media handling. Recently, a reader asked how to turn off PDF thumbnail previews, a feature added in WordPress 4.7 that automatically generates thumbnails for uploaded PDFs. In this practical guide, we'll show you how to easily disable it.
Since WordPress 4.7, the media uploader creates thumbnail previews for PDF files.
This works great for many sites, enhancing PDF previews in your media library.
However, if you're using dedicated PDF plugins for thumbnails and embeds, the built-in feature can cause conflicts, duplicate images, or performance issues.
Disabling it ensures smooth integration with your preferred tools. Let's get started with WordPress 4.7 and newer versions.
This requires adding a simple PHP code snippet. If you're new to this, see our guide on adding code snippets to WordPress (note: original lacked link, preserved as text).
Add this to your theme's functions.php file or a site-specific plugin:
function wpb_disable_pdf_previews() {
$fallbacksizes = array();
return $fallbacksizes;
}
add_filter( 'fallback_intermediate_image_sizes', 'wpb_disable_pdf_previews' );Save the changes. This code returns an empty array for fallback image sizes, stopping WordPress from generating PDF thumbnails.
Test by uploading a PDF via the media library—no thumbnails will appear.
This tweak has resolved PDF issues for many of our clients. For more, check our list of 24 must-have WordPress plugins for business sites.
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