Warrant Canary facts

While investigating facts about Warrant Canary, I found out little known, but curios details like:

A "Warrant Canary" is a way communication companies work around a law that forbids them from disclosing if they've been served a secret government subpoena.

Apple established a 'warrant canary' in 2013 but removed it in 2014, meaning they received a NSA letter

In my opinion, it is useful to put together a list of the most interesting details from trusted sources that I've come across. Here are 2 of the best facts about Warrant Canary I managed to collect.