Computer based wallet, what if i loose HDD but have very old backup?

[postcd]

Hello,

when i download Bitcoin application, create wallet from within it, then i backup whole application folder to external drive.

Then i deposit some coins into wallet and after some time, primary hard drive is lost and so i restore old app backup from time i had no coins in the wallet.

Will that mean i lost money on the wallet? In which file is stored most important data that i want to backup and protect?

[1714967431]

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[1714967431]

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[Lauda]

What Bitcoin wallet are we talking about here? With Bitcoin Core an old wallet backup should work with the -rescan option if:
1) You do not generate more than 100 addresses (as these are pre-generated but hidden).
2) You do not import any other addresses afterwards.

In which file is stored most important data that i want to backup and protect?

For Bitcoin Core you just need to backup the "wallet.dat" file found in your DATADIR. This file is usually under 1 MB.

[cr1776]

Hello,

when i download Bitcoin application, create wallet from within it, then i backup whole application folder to external drive.

Then i deposit some coins into wallet and after some time, primary hard drive is lost and so i restore old app backup from time i had no coins in the wallet.

Will that mean i lost money on the wallet? In which file is stored most important data that i want to backup and protect?

To add to what Lauda stated, it depends on what program and version.  If you are running Bitcoin Core 0.13.0 or greater AND you haven't created a wallet using it before (e.g. this is the first time you are using it to receive bitcoins and didn't run earlier versions/keep the older wallet.dat file), it will create a HD wallet so, although you should back it up, you shouldn't have to worry about the 100 address issue as it is a HD wallet.

[postcd]

the Bitcoin application folder will be newly downloaded, no other wallet. What about mone received tot he wallet after last backup date? These will be lost or no?

[achow101]

the Bitcoin application folder will be newly downloaded, no other wallet. What about mone received tot he wallet after last backup date? These will be lost or no?

If you are requesting a new address (as you should) for every receive, then it is possible that you will lose money. If you use Bitcoin Core 0.13.0+, then you will be fine regardless as long as you don't change (or add) a password. If you use older versions of Bitcoin Core, then after you have used 100 addresses (can be either from requesting new ones or change addresses), your old backup will be useless.

[cr1776]

the Bitcoin application folder will be newly downloaded, no other wallet. What about mone received tot he wallet after last backup date? These will be lost or no?

So for a new install of Bitcoin Core 0.13.0+ you should be fine as long as you handle the passwords as achow101 states since you can recover the initial seed and rebuilt the wallet.

This was not the case previously which is why version numbers are important to check.  (It also never hurts to back up the wallet.dat file anyway, multiple times, plus the password/seed).