A Bitcoin web wallet, also referred to as an online Bitcoin wallet, is a wallet that stores your private keys with an online website. The wallet can only be accessed with your own user-generated password, but considering it is online it is the least secure way to store your Bitcoin. In fact, if you’re using Coinbase to buy Bitcoin you might as well leave your Bitcoins in their web-based wallet as most of these online wallets are connected to cryptocurrency exchanges just like Coinbase. There is still the risk that Coinbase will go bankrupt, but they have the resources to keep your Bitcoin safer than with other web wallets.
If you’re still interested in using an online wallet to store your Bitcoin here are a few options:
GreenAddress is a multisig web wallet that also offers two-factor authentication, and they never store your private keys online. There is a watch only mode to the web wallet, allowing you to check your balance without putting your Bitcoins at risk, even over a public wi-fi connection. There are also apps available for Chrome, iOS, and Android. Sign up here
SpectroCoin is more than just a web wallet for Bitcoin. They also offer an exchange supporting more than 30 currencies, a prepaid debit card for spending your Bitcoins, and a merchant program to accept Bitcoin as payment. There are also versions available for iOS, Android and Windows mobile devices. Sign up here
Coinapult is similar to SpectroCoin because it’s really an exchange and merchant account, but also happens to offer a web wallet for Bitcoins. You can link a traditional bank account for easy transfers in and out of fiat currencies, and also have a feature that allows you to email Bitcoin to someone, or to send and receive Bitcoin via SMS. Sign up here
Xapo says “Xapo combines the convenience of an everyday bitcoin wallet with the security of a deep cold storage vault.” In addition to the vault feature you can buy Bitcoin through Xapo, or use their debit card to spend your Bitcoin or make withdrawals from ATMs. Sign up here