Bitcoin Core · wallet.dat
Bitcoin Core wallet.dat with a forgotten password, in plain language
If you have a wallet.dat from 2012, 2013 or 2014 and can’t remember the password, you are in the case that most often has a way out. Not because it is easy, but because there is almost always memory to recover: those were human passwords, typed by people, not random strings from a manager.
What that file actually is
The wallet.dat is the entire wallet: your keys, your addresses and the history of what you did with them. It is not a backup of something else, it is the thing itself. If it is lost and nothing was written down, the money stays where it is and nobody ever moves it.
When you set a password, Bitcoin Core did not lock the whole file: it locked the part holding the keys. That is why, oddly enough, a protected wallet.dat can be opened and its addresses and balance read without knowing the password. What you cannot do is sign a payment.
Why one wallet.dat is easier than another
Here is the detail almost nobody explains. When you set the password, your computer measured how long a certain calculation took and tuned the difficulty so it would take roughly a tenth of a second. That number was written into the file.
The consequence: a wallet.dat created on a slow 2012 laptop carries a low difficulty and enormous numbers of passwords can be tried per second. One created on a recent, powerful machine carries a much higher difficulty and every attempt costs. Two files that look identical can differ by a factor of a hundred.
That is why, when someone asks me whether their case is workable, the first thing I look at is not the password: it is the file. That number, and only that number, decides how much can be tried. It is explained in the parameters of your file that decide viability.
The old-backup pitfall
This one causes the most heartbreak. In older versions of Bitcoin Core, the wallet held a pool of a hundred ready-made addresses. As you used them, the program created more. If you backed up your wallet.dat in 2012 and kept using the wallet for months afterwards, that backup does not contain the newer addresses.
The result: you restore the backup, everything looks right, and the balance shows zero. The money is not lost: it sits in addresses that copy doesn’t know about. The fix is not to find the password, it is to find the right backup. Newer wallets no longer have this problem.
What decides whether it can be done
| What you remember | Outlook |
|---|---|
| Two or three concrete candidates | Almost always solved |
| The style: a word of yours plus some numbers | A very good starting point |
| Only the approximate length | Depends heavily on the file |
| Nothing at all | Almost never works out |
| It was random, from a manager | It will not work |
What to do today
- Make three copies of the wallet.dat and never touch the original again.
- Search old drives, USB sticks and old emails: there may be another copy, and it may carry a different, older password.
- Gather what you remember from that period: what passwords you used elsewhere back then, whether they were in your own language, whether you tacked the year on the end.
- Check the balance of one of your addresses so you know there is really something to recover before investing time or money.