AI Made Developers 19% Slower. They Thought It Made Them 24% Faster. (opens in new tab)

You probably have a feeling about whether AI makes you faster. Most developers do. And that feeling is almost certainly wrong. In July 2025, a nonprofit called METR published a study that should have broken the internet but mostly got buried under the next wave of AI announcements. They ran a proper randomized controlled trial — the kind of study that drug companies run before putting something on the market — to measure what AI coding tools actually do to developer productivity. Here is what...