Batch-convert WMA (Windows Media Audio) files to MP3 — entirely in your browser, no upload.
This decodes each WMA file and re-encodes it to MP3 using ffmpeg.wasm — a full build of the real ffmpeg audio engine compiled to WebAssembly and loaded straight into your browser. Trim, volume, and fade settings are applied as an ffmpeg filter chain during encoding, and everything runs locally — files never leave your device.
WMA (Windows Media Audio) is an older Microsoft audio format that was the default for Windows Media Player and early iterations of iTunes-era CD ripping on Windows. It's poorly supported outside the Windows ecosystem — many phones, browsers, and non-Windows apps can't play it at all — so converting to MP3 is usually done purely for universal compatibility.
Two things account for most failures. The most common is DRM protection — WMA files purchased or downloaded through old Windows Media Player storefronts were frequently copy-protected, and no browser-based (or any) tool can legally or technically bypass that. The other, rarer, cause is that the file uses WMA Pro or WMA Lossless, variant codecs that aren't always compiled into the ffmpeg-core build this tool loads from its CDN. Either way, if a file fails, the error shown comes directly from ffmpeg itself rather than being hidden, so you can tell which case you're in.
No. ffmpeg.wasm runs the entire decode-and-encode pipeline inside your browser via WebAssembly — your audio never leaves your device. The engine itself (about 25MB) does need to download the first time you use the tool, then it's cached by your browser.