The format or extension of the downloaded attachment will precisely match the original format within the Salesforce org. Let us help you with the steps to download the attachments - 


Scenario 1:

If the "Rename Downloaded Files for Deduplication" toggle on the "About Mass File Download" tab is turned ON.

Follow the below Steps:

1. Open the "Mass File Download" app.

2. Select the subtab "Related Files & Attachments"

3. In the "Select Object" section, choose "Attachment", then hit the "Search" button. 

4. All of your org attachments will display in the table below, Then select Attachments and click on the "Download" Button.

5. Now Open the Downloaded Zip File.

6. It will look like the below image - Actual Attachment Name-Attachment ID.extension

7. You will receive all attachment details on File Mapping.csv, enabling you to view all downloaded attachment details on Sheet as shown in the image below.


Scenario 2:

If the "Rename Downloaded Files for Deduplication" toggle on the "About Mass File Download" tab is turned OFF.

Follow the below Steps:

1. Open the "Mass File Download" application.

2. Select the subtab "Related Files & Attachments"

3. In the "Select Object" section, choose "Attachment", then hit the "Search" button. 

4. All of your org attachments will display in the table below, Then select Attachments and click on the "Download" Button.

5. Now Open the Downloaded Zip File.

6. It will look like the below image - Actual Attachment Name.extension

7. You will receive all attachment details on File Mapping.csv, enabling you to view all downloaded attachment details on Sheet as shown in the image below.