Hi Vinay,
As Mark mentioned above, we need to know your definition of empty to suggest approaches that fits your nee.
Metadata of attachments are stored in sys_attachment table, if you query that table you can identify the size of the attachment.
But if your problem is related to end users adding empty screenshots, we cannot control that behavior.
A blank or white page screenshot still occupies space since the pixels in image stores the white color code and it occupies space on disc.
An alternative approach I would like to suggest is add an attachment type variable, make it mandatory as per your needs and only allow file extensions of type, .eml, .msg, .email, .emlx (Which should cover most common email extensions in windows and apple systems).
In the variable, you may choose to provide instructions on how to download or copy emails from outlook, exchange or webapp or workspace mail or mac, and also inform them that an incorrect attachment could cause cancellation of the request.
Instead of pdfs or image files we can ask users to provide actual email messages, so that there is less chance of providing incorrect approval files as attachments.
This approach may work fine, if the target audience are IT users, but if the catalog item is exposed to non IT end users then it may not be suitable for you and may need to allow users to add even PDFs or image files.
If you want to check this approach on using attachment type variable and you haven't used it before, here are the example screenshots on how to use it.
You can find additional information on this here at below link regarding attachment type catalog variable:
https://docs.servicenow.com/bundle/quebec-servicenow-platform/page/product/service-catalog-management/reference/r_VariableTypes.html#d265662e84
Or alternatively provide help text or instructions and let end user know that, an incorrect or blank attachment may lead to the cancellation of request by fulfillment teams.
Hope this helps!
Thanks and regards,
Subrahmanyam Satti
