Mono to Stereo Converter (Free, Online, No Upload)

Convert any mono audio file to stereo right in your browser. Nothing gets uploaded to a server. Some platforms and players expect stereo audio. This duplicates your mono channel to both left and right so your audio plays correctly everywhere. The conversion runs locally on your device.

Try it in your browser

Loading FFmpeg engine... (~31 MB)

Use the API

curl -X POST https://renderio.dev/api/v1/run-ffmpeg-command \
  -H "X-API-KEY: ffsk_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{
  "ffmpeg_command": "-i {in_audio} -ac 2 {out_audio}",
  "input_files": {
    "in_audio": "https://example.com/input.mp3"
  },
  "output_files": {
    "out_audio": "output.mp3"
  }
}'

Need an API key? Get your free API key to start processing files programmatically.

Common Variations

WAV output for editing

-i input.wav -ac 2 output.wav

With slight stereo widening

-i input.mp3 -af "aecho=0.8:0.88:6:0.4" -ac 2 output.mp3

AAC stereo output

-i input.mp3 -ac 2 -c:a aac -b:a 192k output.m4a

Related Operations

Free Stereo to Mono Audio Converter Online | RenderIO Normalize Video Audio Online Free, No Upload | RenderIO WAV to MP3 Converter Online Free - No Upload | RenderIO MP3 to WAV Converter Online Free, No Upload | RenderIO

Need to process at scale?

Automate this with the RenderIO FFmpeg API. Process thousands of files programmatically or through no-code video automation.

Get your API key