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Merge audio files

Drop your audio files, drag to reorder them, and download the merged result. Everything runs in your browser, nothing is uploaded.

How Merge audio files works

Audio merge concatenates multiple audio files into a single track in your browser. Add your files, drag them into the order you want, and download the combined result. The work is done by ffmpeg compiled to WebAssembly, which handles format normalization, sample-rate matching and the optional crossfade between segments, all on your device with no server involved.

This is the right tool for stitching together podcast segments recorded in separate takes, joining voice memos from a long interview, assembling a playlist into one continuous recording, or combining music parts tracked individually. An optional crossfade smooths the transitions; without it, the files are joined back-to-back precisely.

Written by Bastien Sulyan

How to use Merge audio files, step by step

  1. Drop two or more audio files (MP3, WAV, M4A, OGG are all accepted) onto the upload area.
  2. Drag the file cards into the order in which you want them to appear in the final track.
  3. Choose crossfade duration if you want smooth transitions between segments (0 for a clean cut).
  4. Click 'Merge' and download the combined audio file to your device when processing is complete.

Common use cases

  • Podcast assembly: join a pre-recorded intro, main interview and outro into one ready-to-publish MP3.
  • Interview archival: stitch multiple voice-memo files from a long interview into a single chronological recording.
  • Music production: combine separate instrument recordings tracked as individual WAV files into one mixed-down reference.
  • Audiobook chapter merge: join multiple narration segments into a single chapter file before mastering.

Frequently asked questions

Can I merge files in different formats, such as an MP3 with a WAV?

Yes. ffmpeg normalizes format and sample rate during concatenation. MP3 and WAV files can be joined into a single output. For the cleanest result and fastest processing, all input files should share the same sample rate and number of channels, but the tool handles mixed-format inputs automatically.

What does the crossfade option do exactly?

Crossfade applies the ffmpeg acrossfade filter, which fades out the end of one segment and simultaneously fades in the start of the next, overlapping them for the duration you set. This avoids abrupt cuts between segments. Set it to 0 if you want precise back-to-back concatenation with no overlap.

Is there a limit to how many files I can merge?

There is no hard coded limit in the tool. Practical limits come from available browser memory. Very large collections of high-bitrate WAV files may exhaust memory on devices with less than 4 GB of RAM. For large projects, merging in batches and then merging the results works reliably.

Are my audio files sent to a server during the merge?

No. ffmpeg compiled to WebAssembly runs entirely inside your browser tab. Each file is read into local memory, joined there using the concat demuxer (and the acrossfade and afade filters where requested), and the merged result is offered as a download from your device. Nothing is transmitted to Sunasty's servers.

What output format does the merged file use?

The output format follows the format of the first file in the list by default. If you merge MP3 files, you get an MP3. If you mix formats, ffmpeg selects a compatible output. The output filename is shown before download so you can confirm the format.

Can I reorder files after adding them?

Yes. Each file in the list can be dragged to a new position. The merged output will follow the order exactly as displayed when you click Merge. You can also remove individual files from the list without starting over.