Firekey won't work if Firefox is downgraded

[DanielFragaBR]

I noticed that if I access:

https://firekey.org/

with Firefox 50 and after that I try to access with a previous version of Firefox (for example, 47), it won't show anything (it will only work with Firefox 50 and above)...

[fwenzel]

Sorry I missed this issue. This is actually expected behavior: Firekey does not store anything on the server, everything runs only "offline" in the browser you use it with.

[DanielFragaBR]

Ok, I understand, but why downgrading Firefox versions causes this problem? I mean, even removing cache, database etc doesn't allow it to work again on Firefox 47 (after using it on Firefox 50).