If you use Next.js anywhere but Vercel, here's some bad news: Next.js 15.1+ is broken.
tl;dr: Starting with version 15.1.8, Next.js might break metadata handling for non-Vercel deployments, potentially devastating your search rankings. This is not a bug.
When Did This Happen?
In 2024, Vercel introduced metadata streaming as an experimental feature. This fundamentally changes how Next.js handles metadata.
Traditional approach: Metadata tags (title, description, Open Graph tags) are rendered directly in the HTML
during server-side rendering or static generation.Metadata streaming: These same tags are sent separately after the initial page load, requiring JavaScript execution.
Vercel's Technical Justification
Vercel's stated rationale centers on performance optimization for metadata generation that causes computational bottlenecks. However, this solution creates more problems than it solves:
Metadata is typically static and lightweight (< 1KB)
Server round-trips for metadata are more expensive than inline generation
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