The more detailed claim is 5-6Mbps streams can be reduced to 3-4, so it's more like a 25% improvement methinks. Their first claimed success was with JPEGmini —

The more detailed claim is 5-6Mbps streams can be reduced to 3-4, so it's more like a 25% improvement methinks. Their first claimed success was with JPEGmini — this is a lot more credible since JPEG is a pretty obsolete format that simply continues because it's so well supported. JPEG2000 delivers the purported benefits of JPEGmini for real -- it's just poorly supported. I suspect all they're really doing is fine-tuning compression settings based on differencing input and output using a decent perceptual algorithm. I uploaded a photo straight out of a Nikon V1 onto JPEGmini and got a 2.2x reduction. I could do better than that by dialing down quality until I saw a difference. JPEG fine is way overkill for most purposes, and that's their market.