If you didn't back up your 12 English words seed phrase in paper, along with any manually imported private key or JSON file, you may still be able to regain access to your wallet funds by extracting the Vault Data that is stored by the browser in your computer.
You can read below how to copy your Vault data from Chrome and Brave browsers. If you are using Firefox or any other browser, steps might be different depending on how these browsers store the extension's data locally. Read the specific instructions for Firefox below.
How to extract the wallet Vault on Chrome using a command
In Chrome based browsers (Chrome, Chrome Canary, Brave) you can right-click on the extension window (or on the extension opened in Expand view in a tab: chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/home.html) to use the Web Inspector, then go to the Console tab to type this command, which will show you the {"data":"gewun.......opQ==","iv":"JfVS.....==","salt":"jx4......FI="} part of the Vault directly.
chrome.storage.local.get('data', result => {
var vault = result.data.KeyringController.vault
console.log(vault)
})
Once you have the vault data (which is in JSON format) you can proceed to the Vault Decryptor that you can find in the link below and also see the open-source code at GitHub:
https://metamask.github.io/vault-decryptor/
This Vault Decryptor tool can also be used offline, you just need to use your browser's tool bar > File > Save page as... > MetaMask Decryptor.htm
Open the MetaMask Decryptor.htm file in your browser with your computer disconnected from the Internet.
In the Vault Decryptor page you'll paste the {"data":"gewun.......opQ==","iv":"JfVS.....==","salt":"jx4......FI="} part of the vault data and use the password you set for your wallet in the MetaMask extension. If successful, you'll see the result below the Decrypt button showing the "mnemonic" 12 English words seed phrase, along with any other imported "Simple Key Pair" (private key).
You can now use the seed phrase (and private keys) to restore your MetaMask wallet.
We urge you strongly to make sure that you always backup your seed phrase, and any manually imported private keys, so this never happens again.
How to open MetaMask extension in a tab in Expand view on Firefox to extract the wallet Vault using a command
In Firefox you may need to have the MetaMask extension opened in 'Expanded view' to be able to open the 'Inspect Element' or Web Inspector, checkout this video and follow the instructions below:
you need to enter this in a new tab in Firefox to find the extension's UUID:
about:debugging#addons
you should be able to see the UUID of the MetaMask extension, copy it to add it to the following URL (without the spaces):
moz-extension:// UUID /home.html
This will open the MetaMask wallet in a browser tab in Firefox.
1.- Right-click on the MetaMask wallet that's opened in the full-view tab to see the options
2.- Click the 'Inspect Element' option
3.- Then in the opened window go to the Console tab
4.- Enter this command in the Console and click ENTER:
chrome.storage.local.get('data', result => {
var vault = result.data.KeyringController.vault
console.log(vault)
})
This will show you your encrypted wallet Vault data in text, copy it to a text file to have a backup of it. Now you can follow the instructions in the other video above to decrypt the Vault data with your wallet password.
What if you no longer have access to the Chrome browser but still have access to the computer's files? (Chrome and Windows)
If your computer has crashed and you no longer are able to use Chrome browser or if you've been able to recover your computer files using some backup software, you may still be able to get the encrypted Vault from that backup.
If you were using the Google Chrome browser in Windows 10, you should be able to find the location of the Vault by going to this folder location (you need to be able to see the hidden files):
C:\Users\USER_NAME\AppData\Local\Google\Chrome\User Data\Default\Local Extension Settings\nkbihfbeogaeaoehlefnkodbefgpgknn
In that folder you'll see a file called 000003, open that file with a text editor or code editor software like Atom (https://atom.io/) or sublimetext. Note: the file will not be a .txt file but likely something like a *.ldb. The screenshot below says file type document because it was already opened with a text editor.
In the text editor search for the word "vault" and copy this part that looks like the one pasted below:
{"vault":"{\"data\":\"wwpXXtFCqZkYsWfeEwItZjJ0Cc7mRVjG47Dqh+ztL1PiCG6Izhg+zG0mM+H2ykyjz3X0RNhAE6IVsWFZamcZ47B4sVi4SvUxrMhARm5L3yHPxr3UsyGrOXmthyVMgEGmjwlmnFCNd2nMZ2o8/sRMra8FupurqevnBv57FiYpEEs7gPpFHv6587aL44MmKD8Snv4JLFqiqmlK82Waq5F+Iv9mw2sFVAL9mgZBSgFgbWdB3TsKVB2k\",\"iv\":\"rkUQlNcGTxBE0My7a/bCXw==\",\"salt\":\"HcKyNfGzaRALRQ0DlKgcIe5Uk30iI/M//oG6w8vX8Nk=\"}"}
Remove the two parts in bold. Now use the Search and Replace feature of the editor to change all the \" to "
You would now have something like this:
{"data":"wwpXXtFCqZkYsWfeEwItZjJ0Cc7mRVjG47Dqh+ztL1PiCG6Izhg+zG0mM+H2ykyjz3X0RNhAE6IVsWFZamcZ47B4sVi4SvUxrMhARm5L3yHPxr3UsyGrOXmthyVMgEGmjwlmnFCNd2nMZ2o8/sRMra8FupurqevnBv57FiYpEEs7gPpFHv6587aL44MmKD8Snv4JLFqiqmlK82Waq5F+Iv9mw2sFVAL9mgZBSgFgbWdB3TsKVB2k","iv":"rkUQlNcGTxBE0My7a/bCXw==","salt":"HcKyNfGzaRALRQ0DlKgcIe5Uk30iI/M//oG6w8vX8Nk="}
You can now go to the Vault Decryptor https://metamask.github.io/vault-decryptor/ and paste that in the textfield there, enter the password you set for the extension when you created your MetaMask wallet. You should be able to see your seed phrase and any manually imported private key below if you click the Decrypt button.
For other OS or browser these steps might differ a bit.