Image Zoom is an extension for all Gecko based web browsers. Image Zoom allows the user to change image sizes within a web page. There are several ways the user can zoom images through the interface as well as the ability to zoom single images or an entire page of images.

Image zoom is also a term used for displaying a higher resolution 'zoomed' image upon mouseover or mouseclick of an image on a webpage. This effect has been achieved using Java, ActiveX and more recently JavaScript. The first example of image zoom for web pages to be commercially distributed was created by Tonny Espeset of Norway in 1999, using a Java applet which was supported in all web browsers and on all computer platforms.

ActiveX has also been used for image zoom but compared to Java and JavaScript, it has been limited to Windows web browsers only, and not been popular. The advantage that JavaScript holds over all other zoom applications is that it does not require a plugin (Java can be considered a plugin) and is supported across all browsers and platforms (theoretically). However the same Java applet that was written in 1999 is still supported in all browsers despite the many changes to web browsers and Java support since, which is something that cannot be said about JavaScript.