Client-side HTML encryption tool - https://www.maxlaumeister.com/pagecrypt/
Password-protect HTML documents without server access
PageCrypt is a solution for password-protecting HTML documents using client-side web technology. Just choose an HTML file to password protect, enter a password, and download the password-protected HTML file. HTML Password Protect uses strong encryption to make sure the file cannot be read without the password, employing the PBKDF2 key generation algorithm along with a random salt for key stretching, and the AES256 algorithm for data encryption. Read more about how the tool works by viewing its demo page.
PageCrypt is available on GitHub under the MIT license.