Facebook can ‘magically’ make Android apps run much faster

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Facebook is famously obsessed with efficiency, always searching for better, faster, and cheaper ways to serve its 1.5 billion users worldwide.

After all, explained Facebook software engineer Bert Maher on stage at today’s F8 developer conference, the social network’s mission is to bring people together.

“It’s really hard to do that if your users are staring at a spinner,” says Maher.

And so, as part of its never-ending battle to maximise performance of its smartphone apps, Facebook today introduced ReDex: A free, Facebook-made tool that can hugely speed up Android apps, with minimum effort from the developer.

Internally, Facebook is using ReDex for its own Android app. On Android phones from 2015, ReDex speeds up the time to open the Facebook app by 15%. On Android phones from 2011, ReDex makes it 25% faster to open the app up. And the app itself is another 25% responsive.

Under the hood, ReDex optimises an Android app’s bytecode — the thin, rarely-considered layer of code that sits between an app and the operating system.

Facebook redex

By reconfiguring that bytecode on the fly, ReDex can make it something that’s a little more palatable to Android. Crucially, it does it without requiring any changes to the app itself or to the Android operating system. Just drop ReDex into your app, Maher says, and it gets faster.

“It transforms bytecode magically into better bytecode,” Maher says.

And beyond just the performance, Maher says, ReDex also cuts down on an app’s size, which is a boon to Android users with data plan limits.

ReDex is released today as open source, meaning it’s free for every developer everywhere to download, try out, and customise to their heart’s content. It joins other popular Facebook-grown tools like React Native as an olive branch to developers, and possibly a way to recruit talent.

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