data: URLs, which are a way to embed chunks of data into a URL instead of retrieving the data from the server in a separate call. You've probably never heard of
data: URLs because Internet Explorer doesn't support them, so no one uses them. But they can come in handy in user scripts.
Example: Add a graphical logo at the top of the page
var logo = document.createElement('img'); logo.src = 'data:image/gif;base64,R0lGODlhDQAOAJEAANno6wBmZgAAAAAAACH5BAAAAAAA'+ 'LAAAAAANAA4AQAIjjI8Iyw3GhACSQecutsFV3nzgNi7SVEbo06lZa66LRib2UQAAOw%3D%3D'; document.body.insertBefore(logo, document.body.firstChild);
In this example, the
src of the
<img> element is a
data: URL which contains the entire image data in encoded form. Once the new element is inserted into the page, it will display just
like any other image, but without requiring that the image be stored on a central server. In essence, you can embed images
in your user scripts and distribute them as part of the same file as the rest of your code.