★★★★☆ (Essential, but high responsibility) Verdict: Users should treat wallet.dat as a fragile glass container of value. Do not manually edit it, always maintain backups of the seed phrase (which is superior to backing up the file itself), and be extremely cautious when overwriting the file during migrations.
This file is not a blockchain. It’s a small file (usually a few MB) that lives in your Bitcoin Core data folder. If you have backups of wallet.dat , you can recover your funds even if your hard drive dies. bitcoin core walletdat upd
When you update the wallet format, the client will usually trigger a . This reads the blockchain from the earliest block your wallet had activity to the tip. This can take 4–12 hours on a regular HDD (Solid State Drives are highly recommended). It’s a small file (usually a few MB)