Audio Joiner
Combine songs, voice notes or podcast segments into a single file. Put the tracks in order, choose a crossfade if you want smooth transitions, and save the result as MP3 or WAV without uploading anything.
Drag rows to change the order, or use ▲ ▼. Files are joined from top to bottom.
How to use the Audio Joiner
- Add your audio files by dropping them into the box or clicking to choose them.
- Put them in order by dragging the rows, or use the ▲ and ▼ buttons.
- Turn on crossfade if you want the tracks to blend, and set its length in seconds.
- Choose MP3 or WAV, plus bitrate and sample rate if you like.
- Press Join & download. The joined track is saved and appears in the player for a quick listen.
How crossfade changes the total length
Without crossfade the tracks are placed back to back, so the result is simply the sum of all durations. With crossfade, each pair of neighbouring tracks overlaps by the crossfade time, so every transition shortens the result:
total length = sum of all track lengths − (number of tracks − 1) × crossfade
Example: three tracks of 3:00, 4:00 and 2:30 (570 seconds) with a 5-second crossfade give 570 − 2 × 5 = 560 seconds, or 9:20. A crossfade is never longer than half of the shorter neighbouring track, so very short clips are not swallowed by the fade.
Equal-power vs. linear crossfade
A linear crossfade lowers one track from 100% to 0% while raising the other from 0% to 100%. At the midpoint both play at 50% amplitude, and because uncorrelated music adds up by power rather than amplitude, the transition sounds like a dip in volume. An equal-power crossfade uses a quarter sine and cosine curve instead: at the midpoint both tracks are at about 70.7% amplitude (−3 dB), so their combined power stays at 100% and the loudness feels constant. That is the curve this tool uses.
Which crossfade length to choose
| Content | Suggested crossfade | Why |
|---|---|---|
| Spoken word, podcast segments, lectures | 0 s (off) or 0.3–0.5 s | Overlapping speech is hard to understand |
| Songs for a playlist or party mix | 3–6 s | Smooth transition like a radio DJ |
| Ambient, background or sleep music | 6–10 s | Very gradual, unnoticeable changes |
| Sound effects or ringtone loops | 0–0.1 s | A tiny fade avoids clicks at the joins |
Output settings explained
- Sample rate: 44.1 kHz is the CD and music standard, 48 kHz is used for video. Files with other rates are converted automatically.
- Channels: Auto keeps stereo if at least one file is stereo; mono files are then played equally on both sides.
- Size: MP3 at 192 kbps uses about 1.4 MB per minute. 16-bit stereo WAV at 44.1 kHz uses about 10.6 MB per minute.
Frequently asked questions
How do I merge MP3 files into one?
Add the MP3 files above, arrange them in the order you want, choose MP3 as the output format and press Join & download. The tool decodes every file, places them one after another and encodes a single new MP3 file.
What does crossfade do?
A crossfade overlaps the end of one track with the start of the next: the first one fades out while the second fades in. The tool uses an equal-power curve, which keeps the loudness steady through the transition. Each crossfade makes the total length shorter by the crossfade time.
Can I join files with different formats or sample rates?
Yes. Every file is decoded by your browser and converted to the same sample rate and channel layout before joining, so you can mix an MP3 at 44.1 kHz with a WAV at 48 kHz or a mono voice memo.
Should I choose MP3 or WAV?
MP3 gives small files that play everywhere; 192 kbps is a good default and 320 kbps is near transparent. WAV is uncompressed and lossless but about ten times larger. Choose WAV if you plan to edit the result further.
Is there a file size limit?
There is no fixed limit, but all audio is held in your device's memory while joining. Around one hour of total audio works on most computers; phones may struggle with very long tracks.
Are my audio files uploaded?
No. Decoding, joining and encoding all run in your browser with the Web Audio API and a JavaScript MP3 encoder, so your files never leave your device.