What is GUID

GUIDs are large, enormous numbers that are nearly guaranteed to be unique. They are usually 128 bits long and look like this in hexadecimal:

30dd879c-ee2f-11db-8314-0800200c9a66

The format is a well-defined sequence of 32 hex digits grouped into chunks of 8-4-4-4-12. This gives us 2^128 or about 10^38 numbers.

Here’s the thinking behind GUIDs:

If you pick a huge random number (39 digits long), it’s really unlikely that someone will pick the same one.
GUIDs are not tied to a product. A GUID can be used for people, cars, files, webpages, colors, anything. With regular registration numbers, you start counting at 1 and numbers can overlap. Social Security Number 123-45-6789 is different from ISBN 123456789 which is different from barcode 123456789. This isn’t an issue with GUIDs.
It’s up to the person reading the GUID to figure out the context of the GUID. There are so many GUIDs that you can use them to number everything and not run out.
GUIDs give you a unique serial number that can be used on any item in the universe.