Burp Decoder is a tool that allows the tester to convert raw data into encoded data or to take encoded data and convert it back to plain text. Decoder supports several formats including URL encoding, HTML encoding, Base64 encoding, binary code, hashed data, and others. Decoder also includes a built-in hex editor.
As a web penetration test progresses, a tester might happen upon an encoded value. Burp eases the decoding process by allowing the tester to send the encoded value to Decoder and try the various decoding functions available.