Bitcoin Forum

I received an old wallet backup from a friend who asked me to help them recover the wallet.

I was expecting it to be a wallet.dat file but the name of the file is simply "Bitcoin Wallet backup" and there is not an assigned file type.

I am not sure where to start. Any suggestions would be greatly appreciated.

I run electrum on my PC and it creates / saves a wallet file with the type 'text/plain'. If it is by any chance an electrum wallet, you could try to place it in the wallet directory (http://docs.electrum.org/en/latest/faq.html#where-is-my-wallet-file-located) and then see if it opens up.

Usually in Bitcoin Core it creates a wallet.dat file and in the old multibit classic it created a .wallet file.

Multibit also used an encrypted format such as .wallet.aes or .aes: https://multibit.org/help/hd0.1/files.html (It was a deterministic wallet) and blockchain.info used to use a plaintext JSON format.

So if it's neither of these, you should either ask your friend if he / she can recall the wallet that they've used. Also confirm if that backup is a paper backup or paper wallet, to restore on armory or any other wallet. If you're still stuck, try to back the file first and then create a copy of it and open it with a text editor to observe the contents, maybe you will be able to find how that content is related to a wallet that your friend used by searching online about it.

This sounds like the backup format used by Bitcoin Wallet (https://play.google.com/store/apps/details?id=de.schildbach.wallet&hl=en) on Android.
If the wallet was originally created on a phone, install this wallet and import the backup.

I concur... definitely looks like the backup file naming convention used by "Bitcoin Wallet for Android". If you don't have access to an Android phone, another option may be gurnec's decrypt_bitcoinj_seed utility (https://github.com/gurnec/decrypt_bitcoinj_seed)

It requires you to install Python2.7 and a couple of libraries, but it works pretty well... you'll also need to know the encryption password that was used when the backup was created... and possibly a "spending PIN" if one was set up (the script will prompt for it if required).

If you have the correct password (and PIN if required), it'll find the 12 word seed for the wallet which you can then use to restore the wallet in the BIP39 compatible wallet of your choice.