Which SEO Library Should JavaScript Devs Use in 2026? I Tested Both in Production

I wasted half a sprint shipping a blog platform before someone pointed out our focus keywords weren't appearing in a single H2. Google knew. Our traffic knew. We didn't — because we had no SEO check in our pipeline at all. That started a two-week investigation into JavaScript SEO libraries. I ended up running two of them in a real 200-page Gatsby content site at the same time. Here's what I actually learned — including where each one loses. The Core Problem: Most JS Projects Have Zero SEO Valida