I really like the Sitejet functionality of down-sizing images automatically.
But the Google PagSpeed Insights are telling me that I should still reduce the image size for some images. For future projects: Do you recommend to reduce image to a specific size before uploading to Sitejet?
Sitejet is automatically optimizing the pictures for you. However, my experience is that it all comes down to the detail of the picture itself and the file format.
I use PNG for logos, illustrations, icons and solid shapes. Also use this for small photography if the picture is only displayed small.
JPG I use for photography.
I also now use *.webp occasionally, as it seems that since Safari 14 this is supported by the browser.
I made the experience, that the optimization within Sitejet works fine, BUT as mentioned above it comes down to the detail of the picture. I just uploaded the pictures in original size (5-7 MB) as a test. Some have been reduced immensely to 300-500kb and some have been reduced to 1 MB or more. If you have this case, I would recommend trying and compress it with an external program and see for yourself.
It is not only about how big a picture is but also how detailed. Always ask yourself, if a less detailed picture might also do the trick 
In the end, I made the experience to always check the picture when uploaded. I did upload some heavy compressed pictures, and they looked fine in the program but looked crap on the website on mobile.
Really curious about how other web designers work with their pictures.
Thank you!!
Some of the portraits might have been way to big (I must confess).
So in the future, I will optimize pictures at least a little before uploading.
Google Page Speed Insights “warned” me to use webp format in ordner to speed the page up (marked with ab red warning sign). But honestly, do I really need to convert all images delivered by clients to webp? Tools like this cause clients to have things checked and take the result as give critical issue.
Well, I usually try to use *.webp at more often the moment. BUT I do have a news page with mostly PNG and the score is 70+
Clients tend to use this tools and I think it is really important to tell them how to use the results there and what to expect. You could also ask the client to test the sites of the big companies and let them see for themselves 
Same here.
I think one of the cool things of Sitejet is automatic image resizing because I don’t want to format every single image myself (even before having decided, which images will be used and which won’t). But I can not see a specific “rule” - such as just upload images up to XY kB or MB.
Any other web designers here who want to share your workflow?
Hi Barbara, I tried some different working methods over the past months, but now I normally adapt the size of the image to the use I expect to make of it and then convert it to WEBP format, which already save a lot of space. I use this website for conversions: https://ezgif.com/
I then let Sitejet do its job and only intervene afterwards if Lighthouse or other tools reveal bad scoring of the website because of image formats, sizes or …
kind regards
Mark