Merge Audio
Add the files in the order you want them, choose what happens at each join, and get one file back. Files of different formats and sample rates can be mixed freely.
Runs entirely in your browser. Your files are never uploaded.
How to use Merge Audio
- 1Choose two or more audio files, or drag them onto the box.
- 2Put them in order with the arrows beside each one.
- 3Choose a straight join, a gap of silence, or a crossfade.
- 4Save the result as MP3 or WAV.
Different files, one timeline
A 48 kHz recording from a phone and a 44.1 kHz download cannot be laid end to end as they are: the samples mean different amounts of time. Every file is therefore decoded to one rate before anything is joined, which is also why mixing formats works at all.
Channel counts are reconciled the same way. If any file in the list is stereo, the mono ones are copied to both sides, because writing a mono recording into one channel of a stereo file would put a voice in the left speaker and silence in the right.
Silence or a crossfade
A gap is what chapters and separate takes usually want, and a second or two reads as a deliberate pause rather than a mistake.
A crossfade overlaps the end of one file with the start of the next. The curves used are sine and cosine rather than straight lines, which matters more than it sounds: two unrelated pieces of audio faded linearly lose about 3 dB halfway through the fade, and that dip is audible as a sag at every join.
Order, and getting it right first time
Files are joined in the order shown, which is the order they were added rather than any alphabetical sorting of their names. Use the arrows to move one up or down. The total length under the button updates as you go, so a mistake in the order shows up before the encoding starts rather than after.
Limits
- Everything is decoded into memory at once, so the limit is the total length rather than any one file. Around thirty minutes in total is comfortable on a desktop and less on a phone.
- No per-track volume. A file that is much quieter than the others stays that way, so normalise it first.
- A crossfade cannot be longer than the shorter of the two files it joins, and is shortened to fit.
- The output carries no tags. Joined files lose the titles and artwork of their sources.
Frequently asked questions
- Can I join files of different formats?
- Yes. An MP3, a WAV and an M4A can go into the same job, because each one is decoded before anything is joined. The output is a single MP3 or WAV.
- Does joining MP3s re-encode them?
- Yes, if the output is MP3. Joining at the frame level without re-encoding is possible for files that share a bitrate and sample rate, and it is a narrower tool than this one. Saving as WAV avoids a second lossy pass entirely.
- Why is one of my files quieter than the rest?
- Because it was recorded that way. Nothing here adjusts levels, by design: guessing at a per-file gain would change the balance of a mix you may have set deliberately. Run the quiet file through the loudness tool first, then join.
- How many files can I join?
- There is no fixed count. The practical limit is total length, since all of it has to be decoded in memory at once, and thirty minutes or so is where a desktop browser starts to struggle.