How to join audio files
- Press Add audio files or drop files on the page. You can mix formats, such as MP3, M4A and WAV.
- Put them in order with the ↑ and ↓ buttons, or drag the ⠿ grip. With a keyboard, focus the grip and press the up or down arrow.
- Choose what goes between files: nothing, a silent gap or a crossfade of up to 5 seconds.
- Pick the sample rate, stereo or mono, and the format. The total length updates as you change things.
- Press Preview to check the joins, then Join and download.
Gap or crossfade?
A silent gap inserts silence between files. It suits speech, separate songs and anything where each part should start cleanly. Half a second to two seconds is a common choice between spoken segments.
A crossfade overlaps the end of one file with the start of the next, fading one out while the other fades in. It suits music mixes and background ambience. This tool uses an equal-power crossfade, with sine and cosine curves, which keeps the combined level close to steady when the two pieces are unrelated. Each crossfade shortens the total by its own length, and it can't be longer than half of either file.
Back to back starts each file the moment the previous one ends. MP3 files carry a short stretch of encoder padding at the start and end, and not every browser removes it, so joins between MP3s may have a tiny pause. WAV and FLAC files join without one.
Mixed formats, sample rates and channels
Each file is decoded by your browser and then converted to the output settings before joining. 44.1 kHz is the CD standard and the usual rate for music; 48 kHz is standard for video. When the output is stereo, mono files play in both channels. Choose Mono to fold everything into one channel, which suits voice recordings and halves the size of a WAV file.
The total length shown above the buttons is calculated from the decoded files and your gap or crossfade setting, so it matches the file you download.
Volume differences between files
Joining doesn't change the level of each file, so a quiet voice memo next to a loud song will still jump in volume. If that matters, run the quieter files through the Volume Booster first and normalize each one, then join them here. To trim a file before joining, use the Audio Cutter.
Frequently asked questions
- How many files can I join?
- There's no fixed limit. Everything is held in memory as uncompressed audio, about 20 to 25 MB per minute of stereo sound plus a copy for the joined result, so the practical limit depends on your device. Most computers handle tens of minutes without trouble; phones run out of memory sooner. The tool warns you once the total passes 20 minutes.
- Can I join different formats, like MP3 and M4A?
- Yes. Any file your browser can decode works, and the files can have different sample rates or channel counts. They're all converted to the output settings you choose before they're joined.
- Does joining reduce quality?
- Saving as WAV keeps the decoded audio at 16-bit without further compression. Saving as MP3 re-encodes it, which is lossy, and if your sources are MP3s that's a second round of compression. At 192 or 320 kbps the extra loss is hard to hear for most material.
- Can I trim the files before joining?
- Not in this tool. Use the Audio Cutter to trim or split a file first, or the Audio Editor if you need to arrange clips on a timeline.
- Are my files uploaded?
- No. Decoding, joining and encoding all happen in your browser tab. Your files never leave your device.
Sources
Your files never leave your device. Everything on this page runs locally in your browser: there's no upload, no account and nothing stored on a server.