Safeguarding your crypto wallet means having a reliable backup. Your wallet backup, also called a recovery phrase or seed phrase, ensures that if your device is lost, damaged, or stolen, you can always restore access to your wallet.
Two common backup standards, BIP39 and SLIP39, use a list of simple words to help you safely recover your wallet. In this article, we’ll clearly explain the differences, show which wallets support each standard, and help you choose the one that’s right for you.
Important Security Reminder: Your wallet backup is your key to your funds. Never share your backup with anyone, and never store it digitally — no photos, no cloud storage, no online notes. Write it down securely, and keep it safe and private at all times.
When you set up a new wallet, you’re asked to write down a list of words. This is your wallet backup — a simple, human-readable way to recover your funds if your device is lost, stolen, or damaged.
From this backup, your wallet derives all the private keys that control your funds, predictably and securely. This means your entire wallet — including all your coins, accounts, and addresses — can always be recreated from the same backup.
Your wallet backup can contain:
These formats reduce the chance of mistakes and make wallet restoration straightforward, without backing up each key individually.
Bitcoin Improvement Proposal 39 (BIP39) was introduced in 2013 alongside the launch of the Trezor Model One — the world’s first hardware wallet. It introduced the use of 12-, 18-, and 24-word backup phrases, making it much easier to securely store and recover a wallet.
Today, nearly all wallets support BIP39, making it the industry standard for backup methods.
The wallet starts by generating a very large random number — called entropy. This number is then converted into a list of 12 or 24 words, forming your wallet backup.
The final word includes a checksum, which helps detect mistakes if something is written down incorrectly.
This single backup can recreate your entire wallet: all accounts, addresses, and private keys.
BIP39 relies on a single list of words. If your backup is lost, stolen, or destroyed, you won’t be able to recover your wallet. This is called a single point of failure.
If you want to reduce that risk, SLIP39 offers a solution. It lets you split your backup into multiple parts, so even if one is lost, your wallet stays recoverable.
SatoshiLabs introduced SLIP39 in 2017 to improve on BIP39. Originally called Shamir Backup, it is based on a cryptographic method developed by Adi Shamir that allows a secret to be split into multiple parts, where no single part reveals the secret on its own.
SLIP39 lets you split your wallet backup into multiple shares, which must be combined to restore your wallet. Even if someone finds one share, it’s useless without enough of the remaining shares.
Since 2024, SLIP39 supports upgradeable backups using a 20-word format, starting with Single-Share and allowing upgrades to Multi-Share later.
When setting up a SLIP39 wallet, you can choose:
With this setup, even if one share is lost, your wallet remains recoverable. And an attacker would need at least two shares to gain access.
Want to learn more about upgrading your backup? Check out our guide: Upgrading to Multi-Share Backup.
SLIP39 backups are supported by Trezor Model T, Trezor Safe 3, and Trezor Safe 5.
No. SLIP39 is a different backup standard. To switch, you’ll need to create a new SLIP39 wallet and transfer your funds to it.
Yes. If you start with a 20-word Single-Share backup, you can upgrade to a Multi-Share setup anytime using Trezor Suite. Your original backup will still work unless you choose to retire it.
Yes, but it introduces a new single point of failure. If you lose or forget the passphrase, your wallet can’t be recovered, even with the correct backup. Make sure you write it down and don’t lose it.
BIP39 and SLIP39 are open standards supported by multiple wallets. Even if Trezor were unavailable, you could recover your wallet using other compatible devices or software.
Yes. SLIP39 can be used to securely back up one of the keys in a multisig wallet. If the original device is lost or unavailable, the key can be restored using the SLIP39 shares and imported to a new device.
Up to 16 shares. More shares can offer more flexibility, but they’re also harder to keep track of.
As long as you still have the required number of shares (the threshold), you can recover your wallet. With fewer than the threshold, recovery is not possible — and no usable information about the wallet or keys can be extracted. If you believe one or more shares may have been compromised, it’s safest to create a new wallet and move your funds.
SLIP39 uses cryptography to split your backup securely. Any number of shares fewer than the threshold reveal nothing on their own. Manually splitting a BIP39 phrase (e.g. writing half in one place, half in another) doesn’t offer the same protection and increases the risk of accidental loss or compromise.
A 24‑word backup is longer, but a 12‑word backup is already incredibly secure. Think of it this way: guessing a 12‑word backup is like trying to pick a specific grain of sand from all the beaches on Earth, billions of times over. Even with powerful supercomputers, it would take longer than the age of the universe to find it.
The real key to security isn’t the number of words, it’s how safely you store them. Keep your backup offline, private, and protected from loss or theft.
SLIP39 uses 20 words because each share includes extra information — like group and threshold data — and a stronger checksum to detect errors. The longer format helps ensure each share is unique, verifiable, and secure.
If your BIP39 backup is secure and works well for you, there’s no urgent need to switch. However, if you’re looking for enhanced security, flexibility, or worry about a single point of failure, SLIP39 might be a better option.
Both BIP39 and SLIP39 provide robust security when used correctly. For larger or long-term crypto holdings, SLIP39’s Multi-Share approach is often the safest choice.
Not sure how to secure your wallet — or want to double-check it’s done right?
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Trezor Wallet Backups Explained: BIP39 (12 or 24 words) vs. SLIP39 (20 words) was originally published in Trezor Blog on Medium, where people are continuing the conversation by highlighting and responding to this story.
