If you’ve played with Yahoo! YSlow’s Smush.it tool, you’ll probably notice that it will often convert .GIF files into .PNG files. Ever wonder why they do that? It’s because PNG files are patent-free (though the underlying GIF patent, the LZW algorithm, expired in 2003), contain alpha channels, gamma correction, and two dimensional interlacing. All that gibberish means translates into a better version of a GIF file that also compresses better, about 5% to 25% according to the W3.org.

For you trivia enthusiasts out there, GIF stands for graphics interchange format and was introduced in 1987. It uses the Lempel-Ziv-Welch (LZW) lossless data compression technique that was patented in 1985. CompuServe got into a tiff (haha, get it? TIFF?) Unisys, which held the patent, and the PNG standard was developed.

PNG stands for portable network graphics and nowadays it’s widely accepted as an image format by all major browsers. As a result, it’s becoming more popular as it is generally smaller than GIFs by 5-25%.

You may be wondering where the JPEG, joint photographic experts group, fits in all this. It differs from GIF and PNG in that it’s a lossy compression algorithm (whereas GIF/PNG are lossless) designed for photos.

There you have it, the differences between GIF and PNG (and JPEG!).

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