In our article about how to optimise images for a website, we listed three steps to do so: choosing the right file format, compressing the image, and resizing them to an optimal resolution. Tio (The Image Optimizer) handles the first two tasks for you automatically, which is what makes it best for optimising website images. Here's a little more detail on how the magic happens.
Tio automatically detects certain features of your image. The most common feature here is detecting whether your image uses transparency or not. For PNG images, the file often includes data of the transparency layer even if your image doesn't need it. That's unnecessary bloat which can be easily removed. We analyse files to detect these properties and adjust the output format accordingly.
If a file needs the transparency to be included, we either compress the PNG or convert it to another format that supports transparency — but only if that format results in a lower file size and no visible change in quality. In all other cases, we convert the image to the lightest file format regardless of transparency support.
This is the standard part, although there are slight differences in how The Image Optimizer compresses your files.
With other tools, the compression is meant to work for a variety of use cases. They often give you options to further tweak the compression settings, allowing you to choose the balance of quality and size that works for your use cases. This can include compressing an image to fit some upload criteria, e.g. when sending files to customer support or over email.
With The Image Optimizer, the focus is on website images alone. By knowing this, we can be more liberal with selecting the compression level. And on top of that, we get the liberty to analyse your image and choose the right file format, as described above. With some other use cases, attaching images in formats like WebP or AVIF would not be supported. In most website Content Management Systems, this is not an issue.
This approach allows us to trim up to 35% more of your file size compared to other image compressors:
*In this case, ShortPixel achieved higher compression at the cost of visible quality loss — fine for some use cases, but not ideal for website images where brand presentation matters.