data-url *

URLs with the data scheme are special URLs that embed the resource in-place inside the URL, eliminating the need for additional network calls.

They take the form:
data:[<mediatype>][;<encoding>],<data>

The mediatype is optional and defaults to text/plain with charset US-ASCII.

The encoding can be omitted or specified as base64 (with padding but no newline). base64 introduces a 33% size overhead, but if the encoding is omitted, the data still needs to be percent-encoded, which can negate some of the overhead.

Limitations:

• Size:

  Browsers enforce different maximum size restrictions.

• Security:

  Browser security isolation is based on the origin of a site. Because data URLs do not have an origin, they can be blocked in some contexts depending on the media type, to prevent cross-site scripting or other potential attacks.

• Caching:

  Although embedding the content directly in the URL can save a network trip on the first load, it also bypasses the browser cache which could have effectively saved even more.