To limit the attachment upload to a specific file format, go to:
Form Fields
Click an attachment field.
Upload settings section.
Set Restrict Attachment Types To
This option is used to restrict the type of files allowed to be uploaded in an attachment field (e.g. limit it to images, videos, audio, documents).
💡Note for Audio file
Audio uploads are checked using the MIME type reported by the browser, not a fixed list of filename extensions. The browser must identify the file with an audio MIME type (audio/*).
💡Note for Compressed file
As of the moment, the only supported file extension is zip.
Related
File-type restrictions apply to new uploads. Existing files served directly from Airtable are not checked again when you save the record. New uploads still have to meet the restriction.