Apple has seen its most successful iOS to date, if we’re talking adoption. iOS 9 has now been installed on more than 50% of devices. It took just five days to reach this figure.

Apple’s senior vice president of Worldwide Marketing Phil Schiller was quoted in a statement as saying that iOS 9 is on course to be “downloaded by more users than any other software release in Apple’s history.”

The rate will be good news to Apple – iOS 7 was its last big design update, while iOS 8 brought us a number of new features. However, adoption rates weren’t as strong as they could be. iOS 9 is a comparatively lighter update and sees Apple addressing performance issues rather than attempting to push out too much in the way of new features, which is a well overdue focus.

The news has certainly surprised a number of analysts and users alike, but considering a huge restriction on users last year was the update’s heavy space requirement – 4.6GB. For 5c users on 8GB, or others on the base 16GB models across the rest of the line that put many out of reach if they didn’t wish to delete a whole bunch of apps or photos. On the other hand, iOS 9’s relatively svelte 1.3GB will be much more enticing, and potentially dragged a good portion of the remaining iOS 7 users over to the latest iteration. Furthermore, rather than removing compatibility for older devices, iOS 9 remains available on the iPhone 4s meaning the update will be available to even more users.

Of course, iOS adoption always outshines that of Android – its latest OS, Lollipop, took more than six months to reach 10% adoption, and at close to a year still only sits at 21%.