Free audio joiner, no upload.
A free audio joiner that merges audio files without uploading them. Add as many as you like, drag them into the right order, and get one continuous track back — with a gap between them or a crossfade across the joins. Files that disagree about sample rate or mono versus stereo are reconciled for you, which is the part that usually goes wrong.
Add the files you want to join
Drop them all in at once, or add them a few at a time. Different formats in the same batch are fine — an MP3, an iPhone M4A and a WAV will merge together. Nothing is uploaded.
MP3 · M4A · WAV · FLAC · Ogg · Opus · MP4 · MOV — even old AMR and WMA files. You can also paste one from the clipboard.
Your privacy — live proof, not a promise
- Files uploaded
- 0 bytes
- Processing
- Not started yet
- Your files
- Stay in this browser tab — gone when it closes
- Converter engine
- Not downloaded — only fetched if a format needs it
One download, and it isn’t your audio
Converting to MP3 or WAV needs no download at all. Less common formats use a built-in converter engine (32.5 MB) that comes from this site — not from some other company — downloads once, and is then saved in your browser. Your audio is never part of that download: the engine comes to your files, your files don’t go to it.
Don’t take our word for it: open your browser’s DevTools, watch the Network tab, then convert a file. You’ll see nothing carrying your audio — because this page has no upload feature at all. There is nowhere for your file to go.
Scope note, so this stays exact: the claim is about your files — they never leave this device. The site around it is not claim-free. It loads Vercel Analytics for aggregate page traffic, plus Google Analytics and Ads tags if you accept the consent prompt. Those measure page visits and store-link clicks. They never receive your audio, because nothing does. Full privacy policy.
Converted files are never stored by this page — they exist only in this tab until you download them.
Joining files back together is a recorder problem.
Recorders split long sessions into pieces and leave you to reassemble them. BlackBox keeps a whole day as a browsable hourly timeline and packages each finished day for you. Free on iPhone and Android.
Honest limits of this page
- ·Everything is held in memory, so a dozen hour-long files will strain a phone.
- ·The output is re-encoded, so joining lossy files loses a little detail.
- ·Chapter markers, tags and album art are not carried across.
- ·No fade-in on the first file or fade-out on the last unless you crossfade.
Trim the pieces first
The audio trimmer cuts the fumbling off each take before you merge them, which is much easier than finding it in the joined file afterwards.
Then turn it into text
One merged file is one transcription job rather than a dozen. The free audio to text tool runs on your device too.
How the free audio joiner works without uploading anything
Other sites make you send them your file, do the work on their computers, and send it back. Your browser can do the same work itself — and your file is already here. That is the whole trick.
Add every file
Drop them all in at once, or add them a few at a time. Different formats are fine in the same batch: an MP3, an iPhone M4A and a WAV can go together. Nothing is uploaded at any point.
Put them in order
Use the up and down arrows on each row. The order in the list is the order in the finished file, and the running total tells you how long that will be.
Choose how they meet
Straight cut, a silent gap of a second or two between tracks, or a crossfade where one fades out as the next fades in. The crossfade is equal-power, so the joins do not dip in volume the way a plain fade does.
Merge and download
One MP3 or WAV comes back, built in this tab. If your files disagreed about sample rate or mono versus stereo, the page says so and matches them — that mismatch is the usual reason a merged file plays at the wrong speed.
The thing that usually goes wrong
Two audio files rarely agree. One is 44.1 kHz stereo, the other a 16 kHz mono voice memo. Glue the samples together without reconciling that and the second half plays at the wrong speed, or only in one ear. This page matches every file to the highest sample rate in the set and to a shared channel count first, and tells you when it has done so.
Gap or crossfade
A gap is silence between tracks — natural for separate takes or chapters. A crossfade overlaps them, one fading down as the other comes up, which suits music and continuous speech. The fades used here are equal-power curves, not straight lines: two straight fades crossing at half volume make an audible dip in the middle of every join.
When one file is much louder
Recordings made on different days at different distances almost never match. Turn on loudness matching and each file is measured in LUFS — the same scale streaming platforms use — and brought to the average of the set before joining, so nobody has to reach for the volume halfway through.
What people use it for
Stitch a call recorded in parts
Recorders split long sessions into hourly files. Add them in order and get the whole call back as one track.
Combine voice memos into one note
Ideas captured across a week, joined with a one-second gap so you can hear where each one starts.
Assemble an interview from takes
Reorder freely, crossfade the joins, and match loudness so the quiet answers are not lost against the loud ones.
Make one file for a transcriber
Most transcription tools charge or queue per file. Merging first turns a dozen jobs into one.
Once it is one file, the transcriber will turn it into searchable text — also without uploading it.
Free audio joiner — your questions, answered
How do I merge audio files into one without uploading them?+
Add them all to the list on this page, put them in the order you want, and press Join. Your browser decodes each file, matches them to a shared format and writes one continuous track — all in this tab. Nothing is sent anywhere.
Can I combine MP3 files with M4A or WAV files?+
Yes, in the same batch. Anything your browser can play can go in the list. They are decoded to raw audio first, so the original formats stop mattering the moment they are read, and one file comes out.
Why do merged audio files sometimes play at the wrong speed?+
Because the files had different sample rates and whatever merged them just concatenated the bytes. A 16 kHz recording replayed as if it were 44.1 kHz runs fast and high. This page resamples everything to a shared rate first and tells you when it has had to.
How many files can I join at once?+
No fixed limit. The whole set is held in memory while it is assembled, so the practical ceiling is your device: a laptop handles dozens of ordinary clips, a phone prefers fewer and shorter ones.
What is a crossfade, and should I use one?+
It overlaps two files so one fades out as the other fades in, instead of cutting hard between them. Use it for music or continuous speech. For separate takes, chapters or voice memos, a straight cut or a one-second gap sounds more natural.
One of my recordings is much quieter than the others. Can this fix it?+
Turn on loudness matching. Each file is measured in LUFS — perceived loudness, not just the loudest sample — and brought to the average of the set before joining, so the listener does not have to reach for the volume halfway through.
Is my audio uploaded to a server?+
No. There is no upload endpoint in this feature at all. If you want to check rather than take our word for it, open your browser's developer tools, watch the Network tab while you join files, and you will see nothing carrying your audio.
The rest of the audio toolkit
Also here: the audio converter, the compressor, the transcriber and the browser voice recorder. All free, all on your device.
Record your whole day, privately.
BlackBox is a 24/7 background voice recorder with scheduling, on-device transcription and local storage — about 14 MB an hour. Free on iPhone and Android.