`gulp-custom-filter` is a Gulp plugin that lets you keep or discard files in a build stream using any user‑defined predicate—synchronous, asynchronous (callback) or promise‑based—as well as a set of ready‑made combinators (`not`, `and`, `or`, `all`, `none`) and convenience glob/ignore filters. It’s aimed at front‑end build engineers who need fine‑grained, programmatic file selection beyond simple glob patterns when working with Gulp pipelines.