How self-custody works
A self-custody wallet creates your keys on your own device and backs them up with a seed phrase. Transactions are signed on your device and sent to the network through an RPC endpoint.
The account itself lives on the chain, not in the app. In ethereum.org's words, you hold private keys while the funds stay on Ethereum's ledger. Any compatible wallet can open the same account from the same phrase.[2]
Opening a self-custody account costs nothing. An externally owned account exists as soon as a key pair is generated; no on-chain step is needed to create it.[2]
Each outgoing transaction increases the account nonce by one. Only one transaction with a given nonce can be executed, which stops a signed transaction from being replayed.[2]
Self-custody vs custodial accounts
On an exchange, the company holds the keys and you hold an account balance. It can reset your password, but it can also freeze withdrawals. In self-custody, no one can freeze your wallet, and no one can help if you lose the phrase.
The FTC notes that crypto held in accounts is not insured by the government the way bank deposits are, and that crypto payments typically do not come with the dispute protections of a credit card.[1]
ethereum.org describes two account types: externally owned accounts, controlled by whoever holds the private keys, and contract accounts, which have no private keys and are controlled by their code.[2]
Risks
The main risks move to you: losing the phrase, signing a malicious approval or airdrop claim, or sending to the wrong address. ethereum.org recommends setting spending limits on smart contracts instead of allowing unlimited spend.[4]
Example: setting up a self-custody wallet
Illustrative example of a hardware wallet setup: the device generates a 24-word recovery phrase, which you write on paper or store on a metal plate. Ledger says never to enter that phrase into a computer or smartphone.[3]
Send a small test amount first and compare the recipient address before sending more. ethereum.org lists sending to the wrong address as a common mistake and recommends hardware wallets because the private key stays on the device.[4]
If the device is later lost, you can enter the same words into another compatible wallet to restore access. The words are the wallet; the hardware is replaceable.[3]
An optional BIP-39 passphrase adds a second factor: the same 24 words with a different passphrase open a different wallet. Store the passphrase separately from the words, because the wallet cannot tell you it was typed wrong.[5]
When you restore in another app, it scans addresses until it finds 20 unused ones in a row, the BIP-44 gap limit. Accounts beyond that gap may need to be added by hand.[6]
How to check it yourself
One sign of self-custody is that the wallet showed you a recovery phrase during setup. Under BIP-39 a 12-word phrase encodes 128 bits of randomness and a 24-word phrase 256 bits. If you only log in to an exchange with an email and password, the company usually holds the keys.[5]
Before each transaction, compare the full recipient address with the intended one. Ethereum transactions cannot be reversed once confirmed.[4]
Common mistakes
Storing the phrase as a screenshot or cloud note. ethereum.org warns that screenshots can sync to cloud storage, where a breached account exposes them.[4]
Granting unlimited token approvals. ethereum.org recommends setting spending limits and revoking access you no longer use, because a drainer with an approval does not need your phrase.[4]
Answering "support" messages. ethereum.org warns against replying to messages from "official Ethereum support", and Ledger says it will never ask for your recovery phrase.[3]
Sending crypto to a "giveaway" that promises to double it. ethereum.org lists this as a common scam, and the FTC says only scammers guarantee profits. Report fraud at ReportFraud.ftc.gov or IC3.gov.[1]
The Bottom Line
Self-custody gives you full control of your crypto and full responsibility for its backup.
Educational content, not financial advice.