CODEWITHSUNDEEP
imagebrowserbase64data-uri
danicotra
danicotra

Reputation: 1433

Why it is possible to show a base64 encoded PNG with an "image/jpeg" data URL?

Here's as an example of a base64 encoded PNG data URL (using "image/png" data type, of course):

data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABIAAAASCAYAAABWzo5XAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsMAAA7DAcdvqGQAAAAZdEVYdFNvZnR3YXJlAHBhaW50Lm5ldCA0LjAuMTczbp9jAAAA1UlEQVQ4T62SsQ0CMQxFUzAEA1BQMgIlI1zJCIxAT0HJCBSUlFdQMAQlJWOE78hnObYDIuJLTzr/+/5FkpRz/guh2UM9pLQBWzDXvgVacG4lngncAH08QFgGLcEL0LAX34ROHCBcGaRLiEH+meAMXDhESBlkS3bVrh6KEZetQbOk7FmjmL5M40rKTmQSEJVdeXlCDtcSmgRkz4Ro32Zo+pK7+g7LqqEYjduBjsrzT6Mavl3xhzIJcXDkEBHfTl3WfNln8ARhyQR0sDkX6iU0ewjN38npDdYczGIKuRnZAAAAAElFTkSuQmCC

I noticed that (in Firefox and Chrome) things work even if data type is set to "image/jpeg" (and leaving all the rest untouched) like this:

data:image/jpeg;base64,iVBORw0KGgoAAAANSUhEUgAAABIAAAASCAYAAABWzo5XAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsMAAA7DAcdvqGQAAAAZdEVYdFNvZnR3YXJlAHBhaW50Lm5ldCA0LjAuMTczbp9jAAAA1UlEQVQ4T62SsQ0CMQxFUzAEA1BQMgIlI1zJCIxAT0HJCBSUlFdQMAQlJWOE78hnObYDIuJLTzr/+/5FkpRz/guh2UM9pLQBWzDXvgVacG4lngncAH08QFgGLcEL0LAX34ROHCBcGaRLiEH+meAMXDhESBlkS3bVrh6KEZetQbOk7FmjmL5M40rKTmQSEJVdeXlCDtcSmgRkz4Ro32Zo+pK7+g7LqqEYjduBjsrzT6Mavl3xhzIJcXDkEBHfTl3WfNln8ARhyQR0sDkX6iU0ewjN38npDdYczGIKuRnZAAAAAElFTkSuQmCC

But... Why?

Upvotes: 6

Views: 1596

Answers (1)

wizzwizz4
wizzwizz4

Reputation: 6426

They're both using the image handling subsystem, which ignores the mime type and just goes with the actual format of the image.

Specifically, most browsers will translate the viewing of an image into the viewing of an HTML webpage with an <img> tag in them. Since servers lie and browsers are supposed to be able to show even badly-configured websites, the part of the browser that deals with images will in most cases completely ignore any extensions or MIME types. There was no point programming in an exception for data: URIs.

Upvotes: 6

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