Integrating OpenTelemetry into Next.js applications enhances observability by providing insights into application behavior, and this can be achieved through Vercel's @vercel/otel package or a manual setup. The integration process involves configuring Next.js to push data to a collector, with the instrumentation needing to be explicitly enabled for versions before Next.js 15. Users can utilize default spans available for app and page routers or create custom spans for additional insights. The @vercel/otel package offers easy setup and compatibility across various environments, while manual integration requires specific configurations for Node.js environments and is not compatible with Edge runtime. Highlight further facilitates observability by offering its own scalable collector and additional features such as logging, error tracing, and session replay, which ties client-side events to server-side traces while ensuring data privacy. OpenTelemetry serves as a crucial vendor-agnostic framework, reducing the need for rewriting when switching providers and maintaining a flexible telemetry integration.