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HTMLFormElement: acceptCharset property
Baseline
Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
The HTMLFormElement.acceptCharset property represents the character encoding for the given <form> element.
The specification allows a single case-insensitive value of "UTF-8", reflecting the ubiquity of this encoding (historically multiple character encodings could be specified as a comma-separated or space-separated list).
This reflects the value of the form's accept-charset HTML attribute.
A string which may be a case-insensitive match for UTF-8.
js
let charSet = document.forms["my-form"].acceptCharset;