What is Save for Web in Photoshop
Save for Web is a new feature of photoshop. The save for web option allows you to optimize the files by reducing the file size and without much loss of quality.
How to use Save for web
A new window will open with many options to optimize your image. Simply click optimized tab from top left. You can also select image format in which you want to save like: JPG, GIF, PNG etc.
Here you can also reset the image size.