A string containing one or more unique file type specifiers, separated by commas. These could be file extensions (including the dot, like .jpg, .png, .pdf), or MIME type strings with no extensions, audio/* (any audio file), video/* (any video file), image/* (any image file). If left empty, all file types are accepted.

A valid JavaScript regular expression (as used by the RegExp type) that the input’s value must match in order for the value to pass constraint validation. If this field is empty, no regular expression is applied.