An extended public key is a core feature of cryptocurrencies like Bitcoin that helps manage your addresses and protect your privacy.
Think of it like a "view-only" key for a single crypto account. It allows you, or any software you share it with, to see all transactions and the total balance of that account. However, it cannot be used to spend your funds. Your private keys, which are needed to sign transactions, always remain safely offline on your BitBox02.
From your single recovery phrase, your BitBox02 can create many different accounts. Each of these accounts has its own unique extended public key. This key is then used to generate a nearly limitless number of individual receiving addresses for that account. Using a new address for every transaction is a critical privacy practice, which the BitBoxApp helps you do automatically.
Why are there different formats?
Bitcoin has evolved, leading to different address types (Legacy, SegWit, Native SegWit, Taproot). Because of this, extended public keys come in different formats to tell wallets which address type to generate. You can learn more about these in our guide: Understanding Bitcoin extended public key formats (/extended-public-key-formats).
Note that cryptocurrencies like Ethereum work differently. They typically use a single address per account and do not use extended public keys to generate new addresses in the same way.
Important privacy considerations
Sharing your extended public key allows a third-party service to see all your past, present, and future transactions for that specific account. This can link your entire transaction history together. Only share your extended public key with trusted applications, like tax software or portfolio trackers you rely on.
When would I use this?
For daily use, you won't need to interact with your extended public key. However, it's useful for specific cases like setting up a watch-only wallet or importing your transaction history into tax software. If you need to do this, you can follow our simple guide: How to find your extended public key in the BitBoxApp (/how-to-find-extended-public-key).
- Setting up a watch-only wallet on your phone to track your balance without your BitBox02.
- Importing your transaction history into accounting or tax software.
- Integrating with specific third-party services that need to generate receiving addresses for you.
FAQ Section:
Can someone steal my crypto if they have my extended public key?
No. An extended public key only grants "read-only" access to your account's transaction history and balance. It cannot be used to spend or move your funds.
Does my recovery phrase have just one extended public key?
No. Your recovery phrase is the master seed for your entire wallet. Each separate account you create (e.g., "Bitcoin 1", "Bitcoin 2") will have its own unique extended public key.
Is my extended public key a backup?
No. Your extended public key is derived from your recovery phrase. Your single most important backup is your recovery phrase.
Why should I not re-use Bitcoin addresses?
Re-using addresses allows an outside observer to easily link all your transactions together, which is harmful to your financial privacy.