Headless commerce does not make your store faster
This is the claim that sells the most projects, and the field data does not support it.
Shopify's performance engineering team compared real-user Core Web Vitals across storefront architectures using public Chrome and HTTP Archive data. As of September 2023, traditional Liquid storefronts passed all three Core Web Vitals 59.5% of the time. Shopify's own headless framework, Hydrogen, passed 35%. Next.js and Remix sat around 28-29%, and Nuxt at 22% — every headless framework measured came in below the all-websites baseline of 43%.
Read that again. The company that sells a headless framework published data showing its non-headless option performs better in the wild.
That snapshot predates Core Web Vitals swapping FID for INP in March 2024, so the absolute pass rates have shifted since. The ordering is the point rather than the decimals, and Shopify's INP figures in the same study put Liquid and Hydrogen well ahead of every other headless framework measured.
The reason is not mysterious. A traditional platform arrives with caching, image handling, and asset delivery already tuned by people who do nothing else. Go headless and you inherit all of that yourself. Done by a strong team with a real performance budget, headless can be very fast. Done normally, it usually isn't.
Speed does matter, and it matters commercially. Google and Deloitte's study of 37 retail and travel brands across 30 million sessions found that a 0.1-second improvement in mobile load time lifted retail conversion by 8.4% and average order value by 9.2%. Which is precisely the argument for treating conversion as an engineering problem rather than an architecture one. Fixing speed and buying an architecture are not the same purchase.