What an HTML5 banner is

An HTML5 banner is a small web page, built with HTML, CSS, and JavaScript, that is displayed inside an advertising space on another page. It is not an image or a video: it is code that the browser runs, the same way it runs any website.

Compared with an image or a GIF

A static image doesn’t move. An animated GIF moves, but it is a sequence of photos: it weighs a lot, has few colors, and looks blurry when enlarged. An HTML5 banner draws the text and shapes with code, so it stays sharp at any screen density, animates precisely, and usually weighs considerably less.

What it is made of

• An index.html file with the structure and the text.
• Styles (CSS) that define how each element looks.
• Code (JavaScript) that moves the elements and handles the click.
• Images and fonts, if there are any, next to the index.html.

All of that travels together in a .zip file. The platform that publishes the banner, the ad server, unzips it and displays it.