What is the difference between “image/png” and “image/x-png”?

Question

What is the difference between \"image/png\" and \"image/x-png\"?

Answer 1

According to http://www.w3.org/TR/PNG/#A-Media-type

The internet media type "image/png" is the Internet Media Type for PNG [RFC-2045], [RFC-2048]. It is recommended that implementations also recognize the media type "image/x-png".

So, if you're delivering or uploading a PNG image, 'image/png' is the correct one to use. However, if you're accepting uploads or otherwise interpreting the media type, you are recommended to accept either.

By the way, I found a reference from 2008 that Internet Explorer (version unspecified) was uploading PNG images with a type of image/x-png, so this was a real issue for someone as recently as that.