Find the markings
Look for the DVD region number on the cover or disc and the supported region in the exact player’s documentation. Sony’s support guide explains that a region-coded commercial DVD needs a compatible player region. “All” or region 0 indicates that the disc is not region-restricted; it is not a guarantee of every other aspect of playback.
Do not stop at the region number
Check the player manual for the disc type and video formats it supports. A DVD and a Blu-ray disc are different formats. A computer may need an optical drive and suitable software; a USB socket alone does not establish disc playback capability.
Ask for the label
For a used or imported disc, ask the seller for a legible back-cover photo and confirm the edition. If the region or format is not supplied, treat it as unknown. Use the manufacturer’s documentation for your player rather than assuming it behaves like another model.