The most common formats for images for the web are JPG, PNG and GIF. Also people use TIFF. TIFF and PSD (the Photoshop format) are called lossless formats, as they do not lose quality with editing. JPG can be detrimental to use if we’re expecting to do continued editing on images, as each time it is saved, it loses some of the data, reducing in quality. It is better to work in other formats and then save into JPG only on the final.
A summary of what formats to use, when:
|A logo with only a few colors:||GIF or indexed PNG|
|Anything with transparency:||GIF|
|Local storage of original images:||full color PNG|
|Edited images with layers:||the native format for your image editor, XCF or PSD or whatever.|