Who Is Hosting This has created an infographic that would help us know exactly which filetype is the best to use for saving images.
For instance, it is best to use PNG when saving a your logo image, so that the detail of your logo would not end up being blur.
Scroll down to find out more from the infographic.
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Click on image to enlarge
Click on image to enlarge
Click on image to enlarge
Click on image to enlarge
Click on image to enlarge
Click on image to enlarge
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[via Who Is Hosting This]