Wordpress Image Upload time error : Post-processing of the image failed

WordPress 5.3 introduces this feature but it a bug. Until a WordPress update is released with a fix for the error, this is how you can disable this.

Simple add this line in your child theme functions.php file.

add_filter( 'big_image_size_threshold', '__return_false' );

This same issue I faced after updating my WordPress to latest version 5.3. For a quick solution as of now, you can get over this by uploading the images to the media library first. Currently, if we are uploading images from anywhere else it’s showing the same issue. I hope it helps.

I have tested it on my own website.

Hopefully, team WordPress will fix this soon.

Fixed by increasing client_max_body_size to something like 100/200M(if you use nginx).