The W3C I18N WG in cooperation with WhatWG has created tests for the Encoding specification. In testing the encoding: EUC-JP Our tests found 12646 total errors. In addition 9 of the 11 decoder tests for this encoding failed. Please see: https://github.com/whatwg/encoding/issues/59 Please comment on the above github issue in addition to addressing this bug here. If there are errors in our tests or in the specification, we would very much like to know! [filed for W3C I18N WG]