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Stoyan Stefanov is a Facebook engineer, ex-Yahoo, architect of the YSlow 2.0 performance tool and creator of the image optimization tool!

He's the author of JavaScript for PHP developers (O'Reilly), JavaScript Patterns (O'Reilly), Object-Oriented JavaScript (Packt Publishing), The Book of Speed (online), and a contributor to High-Performance JavaScript (O'Reilly) and Even Faster Web Sites (O'Reilly).

Stoyan is a Zend-certified engineer, blogs at and and speaks at conferences and meetups around the world (Velocity, JSConf, OSCON, Web Directions, Fronteers...)

A Bulgarian-Canadian, Stoyan lives in Los Angeles with his wife and daughters and spends his time biking between home, office, the beach, band practice, flying lessons and kids birthday parties.