You do not need a server to build a useful audio trimmer. Modern browsers can decode an audio file, let the user select a time range, and generate a downloadable clip without uploading the source file anywhere.

This tutorial walks through the core of a small ringtone editor using the Web Audio API and a zero-dependency JavaScript module called ringtone-slicer.

The finished flow is simple:

Read a local file with File.arrayBuffer().

Decode it into an AudioBuffer.