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The Image Size Manager plugin allows site administrators to configure the automatic scaling of large raster images in WordPress.
Since version 5.3, WordPress automatically scales down images whose size exceed 2560 pixels in either width or height. The resized images are renamed with the “-scaled” suffix in the media library. However, automatic rescaling can conflict with the intent of the website’s author(s). Your favorite CMS does not provide administrators with a way to disable this “feature”,nor does it allow users to modify the size at which the scaling kicks in. See <a href="https://make.wordpress.org/core/2019/10/09/introducing-handling-of-big-images-in-wordpress-5-3/" rel="nofollow ugc">this thread</a> for details and an extensive discussion.
Image Size Manager provides both options with a simple, straightforward interface. 
* Access the configuration option from the sidebar menu named after the plugin. 
* By default, simply activating the plugin disables the automatic scaling of “big” images. 
* Note that since WordPress 5.3.1, the automatic scaling feature of WordPress ignores PNG files. Hence, this plugin has no effect on PNG and only affects other raster image formats such as JPEG, TIFF and similar. 
* Image Size Manager has been tested extensively, has no side effect, and should work with any existing theme or plugin.
This plugin will be updated to account for changes in future versions of WordPress, if necessary. Other features, such as configuring additional image sizes generated by WordPress, will be available later.
If you encounter any problems with the plugin, or need extra related functionality, feel free to contact the authors through the comments or the official plugin page.
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Image Size Manager

The Image Size Manager plugin allows site administrators to configure the automatic scaling of large raster images in WordPress.

Shaharia Azam

There are lots of use cases when you upload raw images or large images in your WordPress site. Most of the time it happens if you upload images from your smartphone or DSLR camera that has large resoluation. 
So if you just upload raw image in your WordPress site, you may need to scale it down automatically for you.
In that case, with this Scale Large Image Threshold plugin you can set your threshold. When any image will reach this threshold, it will be automatically scaled down to your preferred size. So you don’t need 
to re-size your large images before uploading to WordPress. Keep capturing your moments and upload. This plugin will help you to resize your image as you want.

Scale Large Image Threshold

Control scaling of big images in Wordpress using big_image_size_threshold filter. Image will be scaled forcefully when it will reach this threshold.

Image Size Manager vs Scale Large Image Threshold