I Ran AI Models Directly in the Browser and Measured What It Did to Core Web Vitals

Everyone is shipping AI features. Sentiment analysis on user input, speech recognition without sending audio to a server, image classification that never leaves the device. The privacy pitch is real, the latency pitch is real. But nobody's asking the obvious question: What does running a neural network in the browser actually cost the user? I decided to find out. I built a benchmark harness, ran four quantized models in Chrome stable, and measured the impact on Core Web Vitals - specifically INP, the metric Google now uses to rank your site. Here's what I found.