A browser-based wallet or wallet service is an online account with an external provider where bitcoins can be stored. Examples include accounts on currency exchange Markets, online Services and with ecommerce transaction processors.
Warning: When storing your bitcoins with a browser-based wallet on a third-party website, you are trusting that the operator will not abscond with your bitcoins, and that the bitcoins will not be stolen by a hacker or the operator's employee or agent, beyond the website operator's control. Ensure you have sufficient recourse and that you can obtain the real-world identity of the website operator. Consider whether the operator is in a financial position to cover any losses that might occur, and what percentage of holdings are kept offline in cold storage as a safety measure from hackers. Storing significant quantities of bitcoins on third party websites is not recommended.
- Use of a browser-based wallet provider may help improve anonymity against third-parties who watch your IP address use.
- An account with a wallet service can generally be established in just minutes.
- Some bitcoin users store some or all of their bitcoins in a browser-based wallet to avoid having to worry about keeping a local wallet secure.
- Since withdrawals can be made to any Bitcoin address, simply using the withdrawal feature to withdraw to an address that is not yours is functionally equivalent to sending a Bitcoin payment when running the Bitcoin client locally.
- Some services offer instant, internal transfers. This allows transactions to complete without having to wait for block confirmations.
Things to be aware of
When bitcoins are stored online, the provider retains full control of those amounts. You are trusting a third party to maintain your Bitcoin balance on your behalf. In comparison, if you run the Bitcoin software yourself, you are in full control of your coins so long as the wallet file stored on your computer is kept secret and secure.
Other relevant things:
- You typically have less anonymity with respect to those who run the online wallet site.
- If a payment is made from an online wallet, the transaction's "from" address is an address for the wallet provider and not an address reserved specifically for the sender. This is because the wallet service provider may service the payment from any coins in its possession - your balance is not associated with any particular coins, any more than your balance at your local bank is associated with any specific bills. Thus if the recipient were to "return" any bitcoins to the same address they were sent from, the sender would not receive those bitcoins.
- Not all wallet providers reserve a bitcoin address for the account holder indefinitely. Bitcoin addresses generally work best when one is assigned for each use. There is the risk of showing an address from a wallet provider in a directory or on a web page (for donations, as an example) as there is the possibility that at the future date when those bitcoins are sent that the intended recipient still has the wallet account. The same concern applies should the wallet provider cease operations.
- There is no trivial way to guarantee that the amount of bitcoins showing for the account holder's balance are truly being held in reserve by the wallet provider.
- Transactions to a Bitcoin address from the same wallet provider are usually completed internally and, if so, will not be processed on the Bitcoin P2P network. Auditing tools such as the Block Explorer will not show any activity for this transaction.
- Some wallet providers allow amounts below 0.01 BTC to be sent if the transaction is to another account holder on the same service. This allows an inexpensive and immediate method to detect if the recipient is using the same wallet provider. For example, MyBitcoin will report an error when attempting to send an amount smaller than 0.01 BTC to a Bitcoin address that is not for another MyBitcoin account.
- The wallet service provider's wallet may be vulnerable to security breaches, loss, or theft. Because Bitcoin transactions are irreversible, there may be limited or no recovery if a provider's master wallet is compromised. Wallet providers who implement preventative controls - such as keeping their reserves in an offline wallet - are likely to be safer.