Wallet Import Format (WIF)

WIF (Wallet Import Format) is a Base58Check encoding of a single Bitcoin private key. It wraps the raw 32-byte private key with a network prefix byte, an optional compression flag, and a 4-byte checksum so a typo at the wallet import screen fails fast instead of silently loading a different key.

What WIF strings look like on mainnet:

• 5... (51 characters) - uncompressed-public-key form. Legacy. Bitcoin Core switched new wallets to compressed keys in version 0.6.0 (2012), so 5... keys mostly turn up in older wallets and paper wallets.
• K... or L... (52 characters) - compressed-public-key form. The standard format for modern WIF.
• 6P... - a BIP 38 encrypted private key, a related format rather than WIF itself. The key is locked with a passphrase, and the wallet must decrypt it before use.

Where you still encounter WIF in 2026:

• Sweeping a paper wallet. Older paper wallets stored a single WIF; sweeping it with a modern wallet sends the coins to your HD-managed addresses in a new transaction.
• One-off private key recovery. A long-dormant address resurfaces, you have the raw private key somewhere, and you need to spend it once.
• Educational tools. Some teaching wallets and Bitcoin developer playgrounds use WIF because it's compact and human-readable.

WIF is a single-key format. There's no derivation, no tree, no children. If you import a WIF and then spend from the resulting address, modern wallets typically don't track future addresses derived from any related key - because there isn't a related key tree. For ongoing custody, modern practice is BIP 39 mnemonic seed phrases driving BIP 32 HD wallets. WIF lives on as the legacy single-key compatibility format.

A WIF also doesn't record which address type the key was used with. The same compressed key can control a 1... address, a wrapped-SegWit 3... address and a native SegWit bc1q... address, so you may need to tell the importing wallet which to look for. Bitcoin Core removed its old importprivkey command in version 30.0 (October 2025). From that version on, a WIF goes inside an output descriptor such as wpkh(<WIF>) or combo(<WIF>), which is loaded with importdescriptors.

Security note: a WIF is exactly as sensitive as a raw private key. Anyone with the string can spend the coins. Treat it like cash, not like a public address.