user119: Is it possible to use Bitcoin client without wallet.dat file, by entering your addresses and being able to see the balance, but without the ability to spend bitcoins? I know that it's possible to backup wallet.dat and use another wallet.dat, but in that way you don't see your transactions and balance and can't label your addresses etc.
If it's not possible in official client (I believe it isn't), are there alternate clients that allow this? The point is to be able to backup wallet.dat and plug it in only when spending bitcoins, but not lose the ability to see your transactions in the meantime.

user7: As mentioned above, btcbalance.net does what you're looking for. 
Also, I have not tested it, but according to this forum post, a Chrome extension called Collate allows you to view your balance without making your bitcoins available for spending:
https://bitcointalk.org/index.php?topic=17158.msg334959#msg334959

In 0.2 you can use the Block Explorer to examine your wallet without
  actually having to run the BitCoin client.  This means you can keep
  wallet.dat on an encrypted partition via TrueCrypt or w/e and you can
  still monitor your account balance (although to send coins you will
  still need to start the BitCoin client for obvious reasons).  In 0.2
  the Block Explorer method of viewing a wallet supersedes the old way
  of connecting to the BitCoin client since the latter requires that
  your private key be stored in memory all the time (which is a bad
  idea).

Collate can be downloaded here:
https://chrome.google.com/webstore/detail/anlcpclkmbeeoglfgbfboogijdkbohkn

user153: The BitcoinJS project implements a client that has no wallet.dat.
It does, however, keep the keys necessary for spending on the mobile client in the html5 local datastorage.
 - http://bitcoinjs.org
WebCoin's implementation: http://www.webcoin.ch

user105: I don't think that it's possible to do anything like that using the official client.
btcbalance.net is a service that lets you store a number of public addresses and view their balance and latest received payments online. I can't vouch for it though since I haven't used it myself.
If you don't want to give your addresses to anyone else you could always just store some links to blockexplorer. http://blockexplorer.com/address/<your_address> will show you the balance and transactions of that address. That's not as convenient as a client/service doing it for you of course.

user23: This is not exactly what you're asking for, but might be helpful. Bitcoin v0.4 supports encrypting wallet.dat, so you cannot spend without entering the password. Basically you would do something like:

make a copy of wallet.dat
encrypt your copy with Bitcoin client v0.4 and set a long random password (one you will easily forget)

Voila, you have just created your read-only wallet. Because of 100 keypool you will even see some new transactions made with original unencrypted wallet.dat
You can download Bitcoin v0.4rc2 here.

119: <p>Is it possible to use Bitcoin client without <code>wallet.dat</code> file, by entering your addresses and being able to see the balance, but without the ability to spend bitcoins? I know that it's possible to backup <code>wallet.dat</code> and use another <code>wallet.dat</code>, but in that way you don't see your transactions and balance and can't label your addresses etc.</p>

<p>If it's not possible in official client (I believe it isn't), are there alternate clients that allow this? The point is to be able to backup <code>wallet.dat</code> and plug it in only when spending bitcoins, but not lose the ability to see your transactions in the meantime.</p>
 7: <p>As mentioned above, btcbalance.net does what you're looking for. </p>

<p>Also, I have not tested it, but according to this forum post, a Chrome extension called Collate allows you to view your balance without making your bitcoins available for spending:</p>

<p><a href="https://bitcointalk.org/index.php?topic=17158.msg334959#msg334959" rel="nofollow">https://bitcointalk.org/index.php?topic=17158.msg334959#msg334959</a></p>

<blockquote>
  <p>In 0.2 you can use the Block Explorer to examine your wallet without
  actually having to run the BitCoin client.  This means you can keep
  wallet.dat on an encrypted partition via TrueCrypt or w/e and you can
  still monitor your account balance (although to send coins you will
  still need to start the BitCoin client for obvious reasons).  In 0.2
  the Block Explorer method of viewing a wallet supersedes the old way
  of connecting to the BitCoin client since the latter requires that
  your private key be stored in memory all the time (which is a bad
  idea).</p>
</blockquote>

<p>Collate can be downloaded here:</p>

<p><a href="https://chrome.google.com/webstore/detail/anlcpclkmbeeoglfgbfboogijdkbohkn" rel="nofollow">https://chrome.google.com/webstore/detail/anlcpclkmbeeoglfgbfboogijdkbohkn</a></p>
 153: <p>The BitcoinJS project implements a client that has no wallet.dat.</p>

<p>It does, however, keep the keys necessary for spending on the mobile client in the html5 local datastorage.
 - <a href="http://bitcoinjs.org" rel="nofollow">http://bitcoinjs.org</a></p>

<p>WebCoin's implementation: <a href="http://www.webcoin.ch" rel="nofollow">http://www.webcoin.ch</a></p>
 105: <p>I don't think that it's possible to do anything like that using the official client.</p>

<p><a href="http://www.btcbalance.net" rel="nofollow">btcbalance.net</a> is a service that lets you store a number of public addresses and view their balance and latest received payments online. I can't vouch for it though since I haven't used it myself.</p>

<p>If you don't want to give your addresses to anyone else you could always just store some links to blockexplorer. <code>http://blockexplorer.com/address/&lt;your_address&gt;</code> will show you the balance and transactions of that address. That's not as convenient as a client/service doing it for you of course.</p>
 23: <p>This is not exactly what you're asking for, but might be helpful. Bitcoin v0.4 supports encrypting wallet.dat, so you cannot spend without entering the password. Basically you would do something like:</p>

<ul>
<li>make a copy of wallet.dat</li>
<li>encrypt your copy with Bitcoin client v0.4 and set a long random password (one you will easily forget)</li>
</ul>

<p>Voila, you have just created your read-only wallet. Because of 100 keypool you will even see some new transactions made with original unencrypted wallet.dat</p>

<p>You can download Bitcoin v0.4rc2 <a href="https://sourceforge.net/mailarchive/message.php?msg_id=28067765" rel="nofollow">here</a>.</p>
