Found old 'key' to bitcoin wallet but don't know which wallet? I was searching through my email today and I think I found a bitcoin private key from 2013. I think it's a BTC private key because I bought 1 BTC that day. It's 33 letters long but I don't know the wallet it's too! Can someone help? Thanks
I think I found a bitcoin private key

So far as I know, a private key is 64 characters long in Hexadecimal (a mix of digits 0-9 and letters A-F only) or 51 characters long in WIF/Base58 (which includes a mix of any uppercase and lowercase letters as well as digits). There's also a mini format that is 22 characters long.


It's 33 letters long

That's likely to be an address. If it starts with a 1 or a 3 then it is almost certainly an address.
You can't recover control over money if you only know an address.
If you are sure you have an address and not a private key, you can safely enter the address into any blockchain explorer to see if there is unspent money at that address.
Obviously you should never enter a possible private key into any website.


from 2013

In late 2013 BIP39 was published - which defined seed-phrases (also called recovery phrases or backup phrases). These consist of a list of 12, 18 or 24 words from a standard list. If you have a set of such words you may be able to use it to recover control.
If I remember correctly, at least one wallet, Electrum, had a different seed-phrase system earlier (maybe a year earlier). So if you find 12 random seeming words, you could try them in Electrum.
Many people startr in Bitcoin without finding out about custodial and non-custodial wallets. If you had an account with a custodial service, you might have old email that might help you recover access to money in and account with some business. However quite a few such businesses are no longer around.