Facebook is at war with the makers of Adblock Plus and other programs that prevent ads from appearing on websites. As ad-blockers become more popular—they prevent tracking and make pages load faster—ad-supported websites are under threat. The social-media giant’s profits ($2 billion in the latest quarter) depend on users consuming advertisers’ messages alongside posts from friends. So Facebook’s engineers recently tweaked its website to make it harder for ad-blocking software to identify ads. A cat-and-mouse game ensued, ending in temporary victory for Facebook—until the ad-blockers develop yet another workaround. Regulators are introducing rules to ensure ads are clearly labelled; any label that can be read by humans can also be read by ad-blockers. But Facebook has an advantage: its users are spending less time on the web and more inside its app, where ad-blockers don’t work. Even if it loses its fight against ad-blockers, it is better insulated from the adblockalypse than most.