This plugin increases your website's performance by reducing image size without an apparent change for the human eye.
The free version supports JPG, GIF and PNG.
Yes, by enabling the option in the settings page. The compression level used will be the default one.
By default, all the thumbnails will be compressed. You can disable this feature from the settings page.
Of course. You can choose a compression level different from the default one for each image in the Media page.
The preview is a very important feature that allows you to see the changes before to make it permanent. By this way, you can test several compression levels and choose that one you prefer. To work, this feature uses a cache into the plugin's directory that must be writable.
Yes but in the premium version. With the free version you can make it manually.
Of course. You can clear it from the settings page.
Yes you can. By enabling the option, you can see more information about the image on the Media page, such as the old size, the new size, the gain obtained by the compression and the compression level used in the compression process.
Yes, of course. You can looking for supported languages in languages directory or create a new one.