The currently accepted answer is JPG. However JPG files are always compressed. One may want to further compress them to save space if the original compression is too high (e.g. 95%).
A clearer and more correct question might be:
Which file format can be arbitrarily compressed degrading image quality?
Another possible improvement in the page is explaining that JPG is most suited for real-life photos with lots of detail and shades, while PNG is most suited for simpler images like logos and rasterized vector graphics.
Your browser information:
User Agent is: Mozilla/5.0 (X11; Linux x86_64; rv:147.0)
Challenge Information:
Working with Images and SVGs - What Are Common Ways to Optimize Media Assets?
Or maybe ‘which image format should you avoid compressing?’
You can make a report on this on Github.
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