The company's iOS 7 adoption widget shows that as of 10:00 a.m. UTC 30.71% of Apple's mobile devices were already running the new OS.
Fortune notes that Apple has sold roughly 700 million devices with half those still in use. That means about 105 million people upgraded their device yesterday.
Notably, the Internet saw a significant spike in traffic yesterday afternoon. Global Nerdy posted the image below from Akamai showing traffic at 112% above normal.
You can find more information about iOS 7 and where to download it here.