Advanced Compression Tools
There are a lot of tools out there for compressing images. I've covered many of the WordPress plugins in a separate article, but there are a few others that you might be wondering about. If you don't see it in this list, shoot me a note and I'll see if it warrants a section here.
The folks behind TinyPNG and TinyJPG have come up with something pretty amazing. They use a very different approach compared to images produced by Google's PSI testing tool, or any of the more common JPG libraries. Most common techniques simply see how far you can go without completely destroying the image quality. However, TinyPNG and TinyJPG use much better algorithms that excel at preserving image quality while also achieving a high rate of compression. This is why we use their software to power the Premium Plus level of our own API.
Anytime Google does something new, folks pay attention. Guetzli is no exception to that, but the hype is a bit ridiculous on this one. First of all, Guetzli is NOT a JPG optimizer. Once you've saved a JPG, it is not useful to re-compress the image with Guetzli. It is a JPG compressor, one time only. It is meant to be used when saving a JPG from a PNG image or other lossless/high-quality input. Then, and only then, does it beat "normal" JPG encoders.
The HUGE disadvantage to Guetzli is the resource consumption. Guetzli uses ridiculous amounts of CPU and memory (the default memory limit is set at 6GB, ouch). Even with all that it is extremely slow. For example, compressing a 1.2MB JPG takes about 7 seconds with TinyPNG, and results in 60% savings. That's already considered "slow" by many, but Guetzli sets a new bar for "slow" at nearly 6 minutes, and the compression is much worse than TinyJPG with only 26% savings.
Additionally, images produced by Guetzli are not optimized. They can be further compressed by any standard JPG optimizer using progressive encoding. Our favorite JPG encoder is mozjpeg, and to date, I have not seen a better lossless JPG optimizer.
This is a compression technology from Dropbox, and is useful only for compressing JPG images "at rest". While it is lossless, you must also have lepton to decompress and view your JPG. Without the decoder, your JPG images are inaccessible. Dropbox compresses images using lepton when they store them to their servers, and then when you want to download or view a JPG, they decompress it on the fly so you can view it again. There are no browsers, and no system viewers that can display lepton-encoded images natively. So if you want to save backup space and lepton-encode all your images, go right ahead. But don't put lepton-encoded images on your website, no one (including you) will be able to view them in the browser.