For the last 3 years, I have been working on a tool that helps me debug ASN.1-encoded data (keys, certificates, Kerberos/CredSSP/SPNEGO/etc tokens, and more), cryptographic operations, and JWTs. This app is available online; you can try it [0] (no sign-in/up needed).
First, this app supported only various cryptography operations.
Then, I started working with JWTs a lot, and I did not like jwt.io design at all. So, I made my own JWT debugger without ads, banners, and other crap.
And last but not least, I also implemented the ASN1 debugger over the years. The best feature is that you can edit the ASN1 tree directly on the page [1].
I'm happy that I wrote this tool. I use it often to help me debug my protocol implementations. I know that some of my friends use the JWT debugger and ASN1 parser from this tool. Maybe some of you will find it helpful too.
The app is open-source [2]. All computations are performed on the client side. Related submissions: [3], [4].
[0]: https://crypto.qkation.com/
[1]: https://news.ycombinator.com/item?id=46255464
[2]: https://github.com/TheBestTvarynka/crypto-helper