David Baumwald

*** 2022-09-12 UPDATE *** 
@matt published a post and codified a final decision that <a href="https://make.wordpress.org/core/2022/09/11/webp-in-core-for-6-1/" rel="nofollow ugc">WebP by default would not be coming to WordPress Core in version 6.1</a>. That being the case, this plugin will not be necessary for users to prevent WebP generation by default as part of the Core upload process.
Proposed to be included in WordPress 6.0 is a new feature to generate and use webp images by default. Specifically, when an image is uploaded, a WebP version of every image subsize is created. According to <a href="https://make.wordpress.org/core/2022/03/28/enabling-webp-by-default/" rel="nofollow ugc">the proposal</a>, one downside is that generating WebP versions along with the original JPEGs will “use an additional ~70% of the storage space to store both file types.” Although this is hugely beneficial to most websites and, more importantly, their visitors, some site owners may not be immediately able to increase the size of their storage to accommodate the additional files. For more information, see the proposal or <a href="https://core.trac.wordpress.org/ticket/55443" rel="nofollow ugc">the Trac ticket</a>.
To help site owners manage the transition, this plugin adds a setting under Settings -> Media to either enable or disable WebP creation on the initial upload of JPEGs. For Multisite installations, the plugin can be activated network-wide or on individual sites.
*** 2022-07-22 UPDATE *** 
Although the original implementation was not merged in 6.0 due to community feedback, changeset 53751(https://core.trac.wordpress.org/changeset/53751) merged an updated implementation that addresses some(but not all) concerns from the community. This merge will be part of the 6.1 release, unless further changes are needed. Some site owners may not be able to immediately cope with doubling their required storage allotment with their host, so the original goal of this plugin remains. The code has been updated to disable WebP creation on upload globally. There is a new ticket discussing the possibility of making this feature into a setting(see https://core.trac.wordpress.org/ticket/56263). However, given WordPress’s core philosphy of “Decisions, Not Options”, it’s unlikely to proceed.

Disable WebP By Default

Thank you for creating this plugin!  It's a shame it's necessary, but I appreciate that you created it to make it easier for site owners to be able to take back control over their sites without needing to know how to add a filter.

Thank you!

Thank you for your work with this plugin (and just keeping track and reporting all the latest WEBP changes, etc.). Great to find so much useful information in the plugin documentation. Very much appreciated!

Thank you

A small plugin to control WebP image creation when JPEG images are uploaded.

brokenlibrarian

SimpleJPEGQuality is a plugin that adds a JPEG quality setting to the WordPress media settings page, which is used to determine the image quality of thumbnails, post images, headers, and other images which have been uploaded and then resized by WordPress. It will have no effect on the quality of the original uploaded images, or that of any images that were resized before this plugin was installed.
This plugin will also affect the quality level of JPEGs resized by plugins that use the image functions of WordPress (such as Auto Post Thumbnail). Image plugins that use their own code (such as Lazyest Gallery, Ungallery, and Post Thumbnail Editor) will not be affected.
The plugin has no extra requirements and has been tested with the twentyten through twentyfourteen themes.
Development on this plugin has halted. Other developers should feel free to use the Apache-licensed code for their own projects.
http://brokenlibrarian.org/tinyplugins/ 
brokenlibrarian@gmail.com 
09/28/14
<h3>License</h3>
Copyright 2014 Christian Wagner
Licensed under the Apache License, Version 2.0 (the “License”); 
 you may not use this file except in compliance with the License. 
 You may obtain a copy of the License at
<pre><code> http://www.apache.org/licenses/LICENSE-2.0
</code></pre>
Unless required by applicable law or agreed to in writing, software 
 distributed under the License is distributed on an “AS IS” BASIS, 
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
 See the License for the specific language governing permissions and 
 limitations under the License.

SimpleJPEGQuality

SimpleJPEGQuality is a plugin that adds a JPEG quality setting to the WordPress media settings page, which is used to determine the image quality of t …

Disable WebP By Default vs SimpleJPEGQuality