If you using images during development, without tools like Gulp and image minimisation – this great online tool allows you to upload your images (20 at a time for free) and download minified versions: tinypng.com/
They also offer a Photoshop plugin and a Pro version (for multiple images).
If using WordPress, we recommend using the Smush plugin (wordpress.org/plugins/wp-smushit/) which will minify automatically on upload.
