Users looking for a crypt to html conversion are mainly searching for a way to recover chat history from WhatsApp backup files.
Tools such as Whatsapp Xtract or WhatCrypt tools allow users to export the chat backups from WhatsApp Messanger (.crypt files) and save them as in a HTML form which when viewed using a web browser will look exactly like your WhatsApp.
For the later versions of CRYPT format, like CRYPT7 or CRYPT12, you will have to first use a tool to convert crypt7 to crypt or convert crypt12 to crypt, before you can work with the backup and extract the data.