Custom laser cutting and engraving sells well online, but every order that depends on a customer's own file is only as good as that file. A little structure on the product page saves you from chasing customers for re-exports after they have paid. Here is a practical setup for Shopify shops.
Keep the list short. Vector formats such as SVG, DXF and PDF cover most design tools. Say clearly whether you also accept images (PNG, JPG) for engraving only, because a photo cannot be cut along an outline. A short list is easier to explain and easier to check.
Shopify product pages do not include a file upload field by default. Shops usually add one with a theme customisation or an app, so the file is attached to the order line item. Collecting the file before checkout is far better than asking for it by email afterwards: the order and the file stay together, and nothing gets lost in an inbox.
Put a short checklist right where the customer uploads, not on a separate FAQ page:
A downloadable template with the artboard size, the cut colour and a margin already set prevents many problems. Link one template per product size if your sizes differ.
Very large files are often a sign of embedded images or thousands of tiny nodes. A sensible upload limit keeps uploads fast and catches those files early.
State in the product description whether you send a proof before cutting, whether small fixes are included, and what happens if the file cannot be used (refund, file fix fee, or a request for a new file). Clear rules up front avoid disputes later.
Customised items are often excluded from standard returns. Say so in your refund policy, and explain that you cut exactly what the customer supplies once the file has been accepted.
Even with good instructions, some files arrive in the wrong format or far too large. Checking at upload time, while the customer is still on the page, is the cheapest moment to catch them.
If you sell laser or CNC work on Shopify and customers upload their own files, CutReady checks the file on the product page before add-to-cart. It accepts only .dxf, .svg and .pdf, with size limits of 256 KB for SVG, 512 KB for ASCII DXF and 2 MiB for PDF, and add to cart stays locked until the file passes ("File OK"). It comes with a 14-day free trial, then 39 USD every 30 days.