The JSON backup file stores your account's information encrypted with the account's password. It's a second recovery method in addition to the mnemonic phrase.

1. In the Polkadot{.js} extension

   1. To export your JSON backup file, click on the three dots to the right of your account and select "Export Account":

   2. Next, you will be asked for your account's password. Enter it, and click on the button to export the account.

   3. Finally, the JSON file will be downloaded to your default Downloads folder. Its filename will be like this:

   [your account address].json

2. Export all accounts in the Polkadot{.js} extension

The Polkadot{.js} extension allows you to export all your accounts added to it in a single "batch" file.

1. Click on the plus icon and select "Export all accounts":

2. Enter a password for the batch JSON file.

3. The JSON file will be downloaded to your default Downloads folder. Its filename will be like this:

batch_exported_account_1641303451011.json

where the number at the end is a Unix timestamp of the time it was exported.