How to Join MP3 Files into One

To join MP3 files into one, open the Join Audio tool, choose your files, put them in the right order and tap Join the files. You download one sound file that plays the pieces one after another.

The files stay on your device while they are joined, and your originals are never changed. This guide explains the order, the gap and crossfade choices, and how to even out the volume.

What you need

• Two or more sound files on your phone or computer, such as MP3, M4A, WAV or voice notes saved as OPUS.
• A recent browser. The page tells you if it cannot read a file.
• Headphones or a quiet place, if you want to check the joins by ear.

Steps to join MP3 files

1. Open the Join Audio tool and tap the box. Choose all the files you want, or add them in several rounds with Add more files.
2. Press play on each file under Listen to each file to be sure you picked the right ones.
3. Put the files in order. Use the up and down arrows beside a file, or drag it to a new place. The numbers in the player list follow the same order.
4. Under Between the files, choose Nothing, a gap of silence, or a crossfade. Tick Match the volume of the files if some are much quieter than others.
5. Choose the File type and Quality. MP3 at 192 kbps is a good start. The page shows the length and the expected size.
6. Tap Join the files. A bar shows the progress, and a Cancel button stops the job. Then play the result once, especially where two files meet, and download or share it.

A gap or a crossfade

A gap adds silence between two files, from half a second to five seconds. It suits separate pieces, such as chapters, voice messages or recordings of different people, because the listener can tell where one ends and the next begins.

A crossfade overlaps the end of one file and the start of the next. The first fades out while the second fades in. It suits music, where you want a smooth change. The overlap shortens the joined file by the length of the crossfade at each join.

With Nothing, the second file starts the moment the first ends.

Matching the volume

Recordings made at different times are often loud or quiet by different amounts, and it is tiring to keep changing the volume. Match the volume measures every file and moves each one towards the same level. It does not push loud parts past the limit, so the sound does not distort. Leave it off if every file already sounds right, or if the changes in loudness are deliberate.

Files that do not match

Files can differ in sample rate, for example 44,100 Hz and 48,000 Hz, or in channels, for example mono and stereo. The tool matches them for you. The joined file uses the highest sample rate among your files, up to 48,000 Hz, and stereo if any file is stereo. Nothing needs to be set by hand.

Choosing the file type

• MP3 plays almost everywhere.
• M4A is a little smaller at the same quality.
• WAV is not compressed, so it is large, but nothing is lost. It suits a file you will edit again.

Joining decodes every file and saves the result once, so MP3 and M4A are compressed one more time. A higher quality keeps more detail.

Common problems

It says my browser cannot read this sound. Update your browser, or save the file as MP3 or WAV first. One unreadable file is named so you can remove it.

The join has a click. Choose a short crossfade of half a second to remove it, or a small gap.

The joined file is very large. Lower the quality, or choose MP3 or M4A instead of WAV.

It is slow. Many long files take a while on a phone. Keep the screen on and the tab open.

Frequently asked questions

Is my audio uploaded?

No. The joining happens inside your browser, on your device. The files never go to our servers or anyone else.

Is there a limit on how many files I can join?

There is no fixed limit. The files are read in small pieces, so the memory of the phone is not filled, but very long results take time.

Can I join a voice note with a song?

Yes. Different types can be mixed, and the tool matches their sample rates and channels. Choose Match the volume if the voice is much quieter than the song.

Will the quality be the same as the originals?

A small extra loss is possible with MP3 and M4A, because the sound is saved again. Choose WAV, or a higher quality such as 256 kbps, to keep as much detail as you can.