WebP format

WebP is a newer format that offers superior compression to Jpeg and Png. It can provide much smaller file sizes at comparable or better quality for both photographic images and screenshots. It is supported by all modern browsers. Recent versions of most graphics tools, like Photoshop support the format. (For older copies of Photoshop, a plug-in is available). Tools such as Imagick and Gimp also support the format.

Examples of quality settings on a photo

File sizes of images in this example. The compression ratio can vary based on image content.

Quality	File size
Original (jpeg)	2.9 MB
100% (lossless)	6.8 MB
95%	2.9 MB
90%	1.9 MB
50%	0.6 MB
0%	0.1 MB

As you can see, the results on photographs isn't always better than the original at 100% -- which is "lossless", but the compression increases rapidly.

_Original vs. 100%._
_100% vs. 90%._
90% vs. 50%._
_50% vs. 0%._

Examples of quality settings on a screenshot

File sizes of images in this example. The compression ratio can vary based on image content.

Quality	File size
Original (png )	157 KB
Lossless	95 KB
100% (lossy)	81 KB
75%	37 KB
50%	31 KB
0% (lowest quality)	9 KB

In general, using a compression of less than 100% (lossless) isn't recommended for screenshots and non-photographic images with large areas of flat colors. Although not the case here, the documentation for the format claims that using a lossy setting can increase the file size for these types of images. The following examples were created with the Photoshop webp exporter. Other tools might provide different results.