WASHINGTON — In the few minutes it will take you to read this story, 3 million new tweets will have flitted across the publishing platform Twitter and ricocheted across the Internet.

The Library of Congress is busy archiving the sprawling and frenetic Twitter canon — with some key exceptions — dating back to the site’s 2006 launch. That means saving for posterity more than 170 billion tweets and counting, with an average of more than 400 million new tweets sent each day, according to Twitter.