You can rename attachments in bulk without downloading them by using the Rename Attachments with Airtable Field automation.
By default, this automation adds a file extension based on the attachment’s reported file type, when that type is available. This may differ from the original filename’s extension. You will only need to specify the actual name of the file, not the extension. For example: To rename a file from Test.pdf to New.pdf, the Airtable field you use to define the new filename would just contain New.
You can also change the file extension by toggling on Rename File Extension.
To set this up, simply follow the steps below:
Select the field that contains the attachments that you want to rename.
Choose the field containing the desired name for the attachment (You can opt for any formula, long text, rich text, or single text field type).
Optional: When selecting the Prefix field to attachment name option, the content of the Airtable field will be inserted as a prefix to the existing name of the attachment.
Test and run
Create the Rename Attachments automation and choose the base and table containing your attachments. Under Setup, select your attachment field as Attachments Field, and the field containing the desired filename as Airtable Field.
Start with a filtered view containing a few test records. In Run, select that view and run the automation. Check the filenames in the selected attachment field before processing the remaining records. Renaming updates the filenames in that field; it does not create a separate output field.