If you lost your JSON file when you first created your account and you want to make another copy, there are two ways to download it now, depending on how you manage your account.  


In the Polkadot extension


1. To export your JSON backup file, simply 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 Downloads folder and its filename will be your account's address as shown in the extension, with an extension of "json".


On the Polkadot-JS UI


1. First, navigate to the Accounts page on Polkadot-JS UI.



2. Next, click the three dots to the right of the "send" button, and select "Create a backup file for this account" as in the screenshot below.


This will only work for accounts that were created directly in Polkadot-JS UI (with type sr25519 or ed25519), not for injected or external accounts.  If you added your account through the browser extension, please scroll down to section 2.



3. You will be asked to enter the account's password, which will also be the JSON file's password.

4. Finally, the JSON file will be downloaded to your Downloads folder and its filename will be your account's address, with an extension of "json".



Export all accounts in the Polkadot extension


The Polkadot extension gives you the option to export all your accounts added to it in a single "batch" file.


1. Click on the (+) icon and select "Export all accounts"


2. Enter a password for the JSON file


IMPORTANT! The password you enter in this step is for the JSON file only! You will need this password in order to restore your accounts from the JSON file. 

This password is unrelated to the individual passwords of your accounts and after restoring from it each account will still need its own password in order to make transactions.


3. The JSON file will be downloaded to your Downloads folder and 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.


That's it, your JSON file has been exported!


If you ever need to restore your account(s), you can do so with this file and your password.  For more details on how to restore check this article.