"should" as in it's your opinion? From the docs it looks like the alpha channel can be encoded lossy as well. https://developers.google.com/speed/webp/docs/cwe

"should" as in it's your opinion? From the docs it looks like the alpha channel can be encoded lossy as well. https://developers.google.com/speed/webp/docs/cwebp#options https://developers.google.com/speed/webp/docs/cwebp#options -alpha_q int Specify the compression factor for alpha compression between 0 and 100. Lossless compression of alpha is achieved using a value of 100, while the lower values result in a lossy compression. The default is 100.