WebCrypt offline usage?

How do I make use of the WebCrypt if my computer doesn’t have Internet connection? My use case is I have my public key in hands and I just would like to encrypt/decrypt file for my own use offline. I don’t want it to touch the Internet and that’s why i use an air gapped computer. I tried to browse https://apps.crp.to/ but it doesn’t work without Internet connection.

How do I make use of my public/private keys for encrypt/decrypt offline with OnlyKey? Is there any way I can access to the WebCrypt offline?

Thank you

You can use onlykey agent - OnlyKey SSH/GPG agent | Docs

Webcrypt is a web app so it requires a web browser or something like this - nativefier - npm