An image compressor reduces the file size of a picture. A 5 MB JPG can come back near 800 KB when the quality is lowered. A PNG that is really a photo often stays large until you save it as JPG or WEBP. The pixels are not resized here. If you need 1920 × 1080 to become 1280 × 720, use resize image.
The result is one file. GIF and animated WEBP keep the first frame only. If the new file is not smaller and the format did not change, the original file is returned. All tools