Non-standard
This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
Summary
The ::-ms-browse CSS pseudo-element represents the button to open the file picker of an <input> of type="file".
Note: Not every property can be used within this pseudo-element. There is a list of allowed properties on the MSDN documentation.
Example
HTML content
<label>Select image: <input type="file"></label>
CSS content
input[type="file"]::-ms-browse
{
color: red;
background-color: yellow;
}
Live Output
Output example
Specifications
Not part of any specification, though Microsoft has a description of ::-ms-browse on MSDN.