Count of API Daily limits on different family sites

Question

API daily limits:

• Key: 10,000
• No Key: 300

How these caps are calculated daily, hitting different family sites?

300/10,000 requests on Stack Overflow
+
300/10,000 requests on Super User
+
300/10,000 requests on Server Fault

OR

300/10,000 requests on Stack Overflow - Super User - Server Fault

Answer 1

The limit is per site. See this question.

These limit are per-site, per-day. So, with a legitimate key, you can make 10,000 requests a day to each site which exposes the API.