Building a Browser-Based NCM File Converter (NetEase Cloud Music to FLAC/MP3)

What is NCM? NCM ( .ncm ) is a proprietary encrypted audio format used by NetEase Cloud Music (网易云音乐), one of the largest music streaming platforms in China. Files downloaded for offline use are stored in this format and can't be played by standard music players like VLC or foobar2000. I wanted to convert my NCM files to standard FLAC/MP3 without installing any desktop software, so I built a tool that does it entirely in the browser. The Tool NCM Converter — a free, open-source web app that converts .ncm files to FLAC or MP3 with album art. Key features: Runs 100% in the browser — no files are uploaded to any server Preserves original audio quality (lossless FLAC or MP3) Automatically embeds high-resolution album cover art Supports batch conversion with drag & drop Works on desktop and mobile Try it here: https://ncm.nr2bj.com/ How It Works The conversion process has 4 steps: 1. Read the NCM Container NCM files are essentially encrypted containers. The file starts with a magic header (