TinyPNG is a plugin that reduces the file size of your photos thereby using less bandwidth and allowing your site to load faster. Typically the compression is between 40-80% of their original size. It does this by combining similar colors and stripping unnecessary metadata. You can choose to preserve copyright metadata, creation date, and GPS location on the original images if you prefer. The image compression happens automatically when you upload the file or you can install and optimize images already in your library. It works for transparent PNGs, animated PNGs, JPGs, and WEBP files.
With the plugin, you can compress up to 500 images per month. After that, you can switch to a paid account. Keep in mind, that different sizes of the same image count toward that 500. BUT by managing your settings to only resize Original image (overwritten by compressed image) you probably won’t exceed that on a normal informational website.
Does TinyPNG change the quality of the image?
Not enough for most people to be able to tell. Go test it out on their website, tinypng.com where you can click and drag a file onto their homepage. Download the compressed image and do a side-by-side comparison with the original file. Let me know if you see a difference.