prebundling

Prebundling is the process of assembling software dependencies into prebuilt bundles before the program runs, with the aim of reducing startup latency and improving runtime performance. It is used across web applications, mobile apps, and desktop software that rely on modular dependency graphs. Prebundling can include vendor libraries, framework code, and frequently used modules.

The approach typically involves analyzing the dependency graph, compiling or transforming modules, and packaging them into one or more bundles with a manifest that maps modules to their bundle identifiers and versions. At runtime, the application loads the prebundled artifact and only fetches incremental updates for modules that have changed since the bundle was created. This reduces on-the-fly processing and network requests.

Common techniques include separating vendor code from application code, producing a cached prebundle that can be distributed via a CDN or local cache, and using build tools that support prebundling. Examples include Vite's dependency prebundling using esbuild, Webpack with DLL plugins, and React Native prebundle steps that prepare dependencies ahead of app startup.

Benefits include faster cold starts and reduced CPU usage during initial load, while drawbacks include the need for cache invalidation, potential staleness of dependencies, and added build and maintenance complexity. Effective strategies include pinning dependency versions, using hashed bundle filenames, and automating invalidation in continuous integration pipelines.

In practice, prebundling trades build-time investment for runtime performance and is a key optimization in modern development workflows for large dependency graphs.