MP3 audio export — Input checklist

Worked example

Before exporting MP3, play your WAV, M4A, FLAC, OGG or Opus file from start to finish: the encoder can only keep what the browser decodes cleanly.

A podcaster with a 40-minute interview recorded as 48 kHz stereo WAV should note three things first: the duration (40:00), the channel count (a single speaker is fine as mono) and the loudest passage. That WAV is about 461 MB, while the same 40 minutes at 128 kbps MP3 is around 38 MB, so the source also tells you how long the browser will take to read it.

Look at how the source was made. A file that is already a 128 kbps MP3 or AAC has lost detail once, and a second lossy pass stacks new artifacts on the old ones. A WAV or FLAC master gives the MP3 encoder the cleanest starting point, which is why you keep it.

The common mistake is trusting the extension. A file renamed from .m4a to .wav, or a recording cut off by a crash, can look fine in the file list and still fail at 12 minutes. Fix it by dragging the playhead to the last minute in any player before you convert, instead of listening only to the first seconds.

Check before you start: write down the source duration and whether clipping (flat-topped peaks) is present. If the loudest part already distorts, no bitrate fixes it, so repair the level first.

Accessible WAV/M4A/OGG/FLAC audio

MP3 audio

The tool reads the whole file into browser memory, so a multi-hour WAV of several hundred megabytes may be slow on a phone; split it first.