Phrase Meaning – What Does ‘Just So You Know’ Mean?

It's a phrase from journalism, meaning withdraw the story from publication, as when a story in an early edition of a newspaper proves to be inaccurate or unfounded (or annoys a big advertiser) and is removed from subsequent editions.

Over the years the phrase has been extended to broadcast and internet journalism.

It was (is?) a television slogan from American broadcaster NBC. They show an educational announcement, and end it with the NBC logo and the words "the more you know".

It became a meme for when someone says something educational, typically used as a sarcastic response when someone mentions a fact that the other person considers trivial or unimportant.