Photo-sharing app Instagram has been downloaded more than 1m times by Android users in its first day on Google’s Play store. The store makes public every app’s number of installs, with Instagram already in its 1m-5m category (so, in fact, it’s probably well beyond the 1m mark now).

More than 430k people had registered to get alerted when the app was finally available for Android, so the early rush isn’t a huge surprise – the release also got heavy coverage on technology blogs. Android remains a small chunk of Instagram’s overall users, since 30m people have downloaded the iPhone version.

Expect it to catch up quickly though. There’s an important network effect here too: the Android release may spur more usage of the iPhone version, as people’s friends sign up – Zynga has identified this trend when it ports its iOS social games to Android.