Resize Image After Upload的作者是ShortPixel,目前有80,000+个有效安装。已经Tested with 5.3.3版本的wordpress。
Description

A free, fast, easy to use, stable and frequently updated plugin to resize your images after upload. Supported by the friendly team that created ShortPixel

This plugin automatically resizes images (JPEG, GIF, and PNG) when they are uploaded to within a given maximum width and/or height to reduce server space usage, speed up your website, save you time and boost your site’s SEO.
Imagine that nowadays images can be over 4-5MB and using this plugin you can reduce them to 100-200KB with no extra effort on your side!

In addition, the plugin can force re-compression of uploaded JPEG images and convert PNGs to JPEG (if they don’t have a transparency layer), regardless of whether they are resized or not.

Is that simple, just give it a try, it is safe and free!