By default the following image is displayed for a project:
You can change this default image by adding, next to your
QGS file, a image with the exact project name and
Extensions can be
.avif. We recommend the first format.
Example, if the project is called
montpellier.qgs you must add, next to it, an image named
montpellier.qgs.png. Note that the image has the project extension
.qgs too in its filename.
To save bandwidth and speed up the projects page load you must:
Create images with a width of 250 pixels maximum.
.webpas it produces images that are much smaller than other formats and is very well supported by modern browsers. For even smaller images you can use
.avifbut you should take care of browser compatibility.
Use Squoosh or any other tool to convert from one image format to another and reduce quality as much as it is possible without being visually perceptible.
To see the thumbnail immediately, it might be needed to clear the cache in your web browser and force reload the page from the web browser.
Otherwise, the thumbnail will be displayed automatically in a few hours, when the web browser will understand that the image has changed. Web browsers tries to save some network requests.