How to get information about a product (its composition) from a barcode? Which way to look?

Question

Data request

I want to understand how to get information about a product, specifically interested in its composition, from a barcode? I want to make a scanner.
Various pages are googled that say general information, such as that it is a "walnut", but no more. In which direction do you look?

Answer 1

The barcode gives out just an identifier. With this identifier, you need to make a request over the network to the api with the goods, which will give out everything you need.

Answer 2

Barcode database (gtin) with free access