Fancybox is an easy to use plug-in that gracefully enlarges images in your posts and pages when a reader clicks on them.

When you upload an image to your blog using the “Media>>Add New” tab in the dashboard, WordPress automatically saves that image in up to four different sizes: thumbnail, medium, large, and full-size, depending upon the image’s original size. (When you “Insert into Post,” you can see which sizes are available.)

If you activate Fancybox, and a reader clicks on the image, a popup will display the image in its largest available size.

The plug-in will automatically convert all images in your blog that don’t have pre-existing links. If you don’t want the Fancybox effect on some images (perhaps you are displaying them in their largest size already), you can delete the link, and the popup will not appear. (This can be done best in the HTML view).

The plugin has a page with many customizable settings to change the borders, zoom rates, overlay color and opacity, but the default settings work fine for starters.

One warning: Fancybox does not work well with posts that use WIKI Inc plugin to “include” wiki page content. If the wiki page that you include has images in it, the Fancybox effect will not work.

Here is a post with a thumbnail image:

And when you click on the thumbnail, Fancybox does its magic:

Have fun with this useful and easy to use plugin!