Sitecore Layout Service

For sites built with Sitecore JSS, the front-end application retrieves presentation details from the Sitecore Layout Service. Layout Service describes all of the placeholders, renderings, data sources and other details needed for the front-end application to generate presentation logic.

Uniform hooks into Layout Service in order to include settings that enables decoupled tracking, personalization and testing.

Build-time vs. runtime

With standard Sitecore, the front-end application calls Layout Service at runtime. The Sitecore CD instance is responsible for running the logic that determines the output that is returned for each visitor request.

With Uniform, Layout Service is called either at build-time (if using Deploy) or at runtime, but on a very limited basis (if using Optimize without Deploy). The logic responsible for generating Layout Service output that is appropriate for the visitor runs on the CDN.