Data URI

The data URI scheme is a uniform resource identifier (URI) scheme that provides a way to include data in-line in web pages as if they were external resources. It is a form of file literal or here document. This technique allows normally separate elements such as images and style sheets to be fetched in a single request, which may be more efficient than multiple HTTP requests. As of 2015^[update], data URIs are fully supported by most major browsers, and partially supported in Internet Explorer and Microsoft Edge.

The syntax of data URIs was defined in Request for Comments (RFC) 2397, published in August 1998, and follows the URI scheme syntax. A data URI consists of:

Examples of data URIs showing most of the features are:

The minimal data URI is data:,, consisting of the scheme, no media-type, and zero-length data.

Thus, within the overall URI syntax, a data URI consists of a scheme and a path, with no authority part, query string, or fragment. The optional media type, the optional base64 indicator, and the data are all parts of the URI path.

An HTML fragment embedding a picture of a small red dot:

In this example, the lines are broken for formatting purposes. In actual URIs, including data URIs, control characters (ASCII 0 to 31, and 127) and spaces (ASCII 32) are "excluded characters". This means that whitespace characters are not permitted in data URIs. However, in the context of HTML 4 and HTML 5, linefeeds within an element attribute value (such as the "src" above) are ignored. So the data URI above would be processed ignoring the linefeeds, giving the correct result. But note that this is an HTML feature, not a data URI feature, and in other contexts, it is not possible to rely on whitespace within the URI being ignored.

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