How to merge audio files

Two meanings of "merge"

People use the word for two different jobs. Joining plays one file after another, which is what you want for podcast segments, voice notes or a playlist as one file. Mixing plays files at the same time, for example a voice over a music bed. This page is about joining; the browser tool below joins files end to end and does not overlay them.

With Audacity (free, Windows, Mac and Linux)

Audacity is a free, open-source audio editor. Choose File, Import, Audio and select your files, which open as separate tracks. Select all the tracks and use Tracks, Align Tracks, Align End to End, which Audacity's manual describes as moving each track so it starts where the previous one ends. Then File, Export and pick MP3 or WAV. To mix instead, use Tracks, Mix.

It is powerful, but it is a full editor to install for a simple join, and there is no phone version.

In the browser, without uploading

The merge audio tool takes MP3, WAV, M4A, AAC, OGG, Opus and FLAC files, or the sound of a video, and needs at least two.

• Order: files are joined top to bottom; use the arrows to reorder.
• Between files: nothing (straight on), 1 or 2 seconds of silence, a 2 second crossfade, or a 5 second crossfade for a DJ-style blend. A crossfade is shortened if a clip is too short to hold it.
• Save as: MP3 at 128, 192 or 320 kbps, or a 16-bit WAV with no quality loss but a larger file.
• Mixed formats: an MP3, a WAV and an M4A can be joined together; everything is converted to 44.1 kHz. If any file is stereo, mono files play in both ears.

In our test, a 3 second MP3 and a 2 second WAV joined with a 2 second crossfade made one 4 second, 192 kbps MP3 (the crossfade was shortened to 1 second because the second clip was short). The result is saved as merged.mp3 or merged.wav.

Everything happens inside your browser tab, so the audio never leaves your device. To cut the start or end of a file before joining, use trim audio first, or read how to trim an MP3 file.

Keeping quality

Every join re-encodes the sound once. Saving as WAV keeps every sample; MP3 is encoded once at the bitrate you choose, and at 192 kbps or more the difference from the originals is very hard to hear. If one source is much quieter than another, fix the volume first with the volume booster, because joining does not even them out.

Questions