Where do websites get the exchange rates of various banks from?

Question

API

Greetings, tell me where the sites take the exchange rate from local banks?
Is there any service that contains several exchange rates of banks?
Here's an example:

Answer 1

Some banks provide this data in the form of an API,
some simply post it on the site in clear text.
Then someone parses this data himself, someone parses and distributes this data in the form of an API, and so on.
Not sure if there is a recipe

Answer 2

For example: https://www.moex.com/a2193