Use the Save For Web dialog box to preview the effects of different optimization options on a photo you want to share on the web. The process is simple. Open a photo and choose File > Save For Web. Then choose a format from the file format menu (GIF, JPEG, PNG‑8, or PNG‑24) and set options as desired. (The file format menu is directly beneath the Preset menu.) This saves a copy of your file, without overwriting the original image.
Optimization options appear on the right side of the Save For Web dialog box. In addition to selecting a web file format, you can choose compression and color options, preserve background transparency or set background matting, and change the size of the image. You can use predefined settings (by choosing a format from the Preset menu), or select format-specific options to fine-tune the optimization.
The image windows show your original image (on the left) and a preview of the optimized image (on the right). Under each window is optimization information—the current settings, the size of the optimized file, and the estimated download time. As you make adjustments, the information under the optimized image changes to reflect your new settings.
A small toolbox is located in the upper-left corner of the dialog
box. To view different areas of an image, select the Hand tool and
drag to bring those areas into view. To zoom in on an image, select
the Zoom tool
and
click in a view; then hold down Option, and click again to zoom
out. (Alternatively, you can use the Zoom box at the bottom of the dialog
box.) To create matte colors, use the Eyedropper Color tool.