Join audio files into one, in the order you want
The Audio Joiner puts 2 to 50 audio files one after another and saves them as a single file. Drop in MP3, WAV, M4A, AAC, FLAC, Ogg or Opus files — they can be mixed — drag them into order, choose whether they meet with a straight cut, a short silent gap or a smooth crossfade, and download the result as MP3, M4A, WAV, FLAC or Ogg.
Use it to turn a folder of voice notes into one recording, stitch audiobook chapters or lecture parts together, build a party mix with crossfades, or add an intro and outro jingle to a podcast. Files with different sample rates or channel counts are matched automatically, and the optional Match loudness setting stops one quiet recording from disappearing between two loud ones.
Everything happens in your browser. Your files are decoded, joined and encoded on your own device, so private recordings never leave it. Only the open-source Mediabunny library (MPL-2.0) and, for MP3 or FLAC output, the LAME (LGPL) or libFLAC (BSD) encoder are downloaded, once.
How to use the Audio Joiner
- Drop your audio files onto the box, or click it to choose them. Add more later with Add files.
- Put them in order: drag a row’s handle (mouse or finger), use the arrows, or press Sort by name. Press ▶ to listen to a file.
- Under Between files, choose a straight join, a silent gap or a crossfade, and set its length in seconds.
- Tick Match loudness if the files were recorded at different levels.
- Choose the output format, bitrate, sample rate and channels — or keep the automatic choices — then press Join audio.
- Listen to the result in the player and press Download joined audio.
Audio Joiner features
Up to 50 files, any mix of formats
Join MP3 with WAV, M4A, FLAC, Ogg Vorbis, Opus or WebM audio in a single pass; each file shows its format, length, sample rate and channels.
Reorder by drag, tap or name
Rows can be dragged with a mouse or a finger, nudged with arrow buttons, or sorted by file name with natural number order (2 before 10).
Gaps or crossfades
Leave 0.1–30 seconds of silence between files, or blend each file into the next with an equal-power crossfade that keeps the volume steady through the overlap.
Sample rates and channels matched
A 48 kHz file joined to 44.1 kHz files is resampled with a windowed-sinc filter, so pitch and speed stay correct; mono files play on both sides of a stereo result.
Match loudness
Each file’s average level is measured, ignoring silence, and the files are brought to the middle level — but never pushed so far that a peak would clip.
Timeline with zoom
A waveform of the joined result shows where every file starts and where crossfades overlap; zoom in to inspect a join before you export.
Straight join, gap or crossfade?
A crossfade overlaps the two files, so it makes the joined audio shorter: three files with 2-second crossfades lose 4 seconds in total. The crossfade uses equal-power curves (a quarter sine in, a quarter cosine out), which keep the combined loudness constant for unrelated music, whereas plain linear fades would cause an audible dip in the middle. For very short clips the crossfade is shortened automatically to fit.
| Join | What you hear | Good for |
|---|---|---|
| Straight join | The next file starts on the very next sample | Parts of one recording, audiobook chapters, gapless albums |
| Silent gap | A pause of the length you choose between files | Separate songs, voice notes, language lessons, playlists for a speaker |
| Crossfade | The end of one file fades out while the next fades in | DJ-style mixes, workout and party playlists, background music beds |
Which output format should I pick?
Same as input uses the format of the first file. MP3 plays everywhere — 128 kbps is fine for speech and 192 kbps for most music. M4A (AAC) sounds a little better than MP3 at the same bitrate and suits iPhones and Apple Music. WAV and FLAC are lossless: choose them if you will edit the result further, because every lossy re-encode loses a little quality. Ogg (Opus) gives the smallest files for speech.
As a rule of thumb, an MP3 needs bitrate × seconds ÷ 8 bytes: a one-hour join at 128 kbps is about 57.6 MB, while the same hour as 16-bit stereo WAV at 44.1 kHz is about 635 MB.
Joining vs mixing vs cutting
This joiner plays files one after another. To play files at the same time — a voice over background music, or two instruments layered — use the Audio Merger, which mixes tracks with their own volume and start time. To cut a long recording into pieces, use Split Audio, and to trim the start or end of one file before joining it, use the Audio Cutter. Long silences inside recordings can be shortened first with the Audio Silence Remover.
Audio Joiner FAQ
How do I join MP3 files into one?
Drop the MP3 files on this page, drag them into the order you want and press Join audio. Keep the output format on MP3 (or Same as input) and download the joined file.
Is this audio joiner free and private?
Yes. It is free with no sign-up, watermark or upload: your files are decoded, joined and encoded inside your browser and never leave your device.
Can I join files with different formats or sample rates?
Yes. You can mix MP3, WAV, M4A, FLAC and Ogg files. Files are resampled to one sample rate — by default the rate most of them use — and mono and stereo files are matched, so nothing plays too fast, too slow or on one side only.
Why is there a tiny pause between joined MP3 files?
MP3 encoders add a few milliseconds of silence at the start and end of every file (encoder delay and padding). When MP3s are decoded and joined, those milliseconds remain. For truly gapless results, join the original WAV or FLAC files if you have them.
How long can the joined file be?
There is no fixed limit. Files are decoded one at a time while joining, so hours of audio usually work on a computer; phones may struggle with very long WAV or FLAC output.
Does it re-encode my audio?
Yes — the audio is decoded and encoded again. Choose WAV or FLAC for a lossless result, or a high MP3 or AAC bitrate to keep any quality loss inaudible.