Free Online Audio Merger

Concatenate multiple audio files into one MP3 in the order you pick. No cap on the number of files (total ≤200MB), no restriction on input formats.

Merge Audio Files
Select at least 2 audio files. They will be joined in top-to-bottom order.

About this online audio merger

Merging audio is a basic task, but desktop apps (Audacity, Adobe Audition) carry a steep learning curve. OneAudio Merger boils it down to two steps: upload multiple files in order → click merge → download. No need to know about sample rates, bitrates, codecs — the server normalizes them for you.

The backend uses FFmpeg's concat filter together with the mergeToFile API — guaranteeing that files with different sample rates (44.1kHz + 48kHz) or different bitrates (128kbps + 320kbps) still join seamlessly without clicks at the transition. Output is standard 192kbps stereo MP3, compatible with every device.

  • Merge any number of files (total ≤200MB)
  • Mix formats freely: MP3 + WAV + M4A + FLAC in one pass
  • Auto-resamples to 44.1kHz to avoid clicks at joins
  • Preserves the upload order exactly
  • 192kbps stereo MP3 output — ready to use
  • Server-side processing, no browser RAM hit

Merge multiple audio files into one

  1. 1

    Upload every file you want to merge

    Click to pick many, or drag-and-drop — hold Ctrl/Cmd to multi-select. List order matches output order.

  2. 2

    Review the order (re-pick if needed)

    Files are joined top-to-bottom as shown. Remove wrong files with the X button. Add more if anything's missing.

  3. 3

    Click Merge and download the full MP3

    mergeToFile runs server-side in 15-40 seconds depending on count. Result is one continuous MP3.

Real uses of audio merging

Build a long road-trip playlist
Glue 20 tracks into one MP3 for offline playback on a car CD head unit with no playlist support.
Stitch interview segments together
Three separate interview files → one seamless podcast ready to publish.
Assemble an audiobook from chapters
15 chapters recorded separately → a single file for your audiobook player.
Combine background music + voice-over
Voice intro + main BGM + voice outro → one complete episode.

Frequently asked questions about audio merging

How is merging different from mixing (overlapping)?
Merging (concat) places files end-to-end in time — file 1 finishes, then file 2 starts. Mixing overlays files at the same time — music and voice play together. OneAudio Merger does concat, not mix yet.
Any fade in/out between files?
No. Files join hard, no crossfade. For crossfades, you'd need Audacity or Reaper.
Can I merge files with different sample rates?
Yes. FFmpeg auto-resamples to a common rate before joining so there are no errors.
Where do I reorder the file list?
In the file list after upload. Drag-to-reorder isn't in yet — delete wrong entries and re-upload in the right sequence. (On the roadmap.)
Any limit on file count?
No hard cap, but total size must stay ≤200MB.
Can I EQ or boost after merging?
Yes. Download the merged MP3 and upload it into Equalizer or Booster for further tweaks.