Audio Joiner
An audio joiner for stitching clips into one track: queue them in order, set a crossfade if you want them to blend, then export M4A, WAV, Opus, or FLAC.
The joined track
Clips
Drop the clips to join
MP3, WAV, M4A, OGG or FLAC · two or more, in the order you want them
Tracks, in join order
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Joined length
Add two or more and the joined length lands here: the sum of their durations, less one blend per seam.
How to use
- Drop your clips on the Clips box, or press Choose files and pick a batch.
- Check the list that appears: one row per clip, each showing its place, its length and its rate, merged top to bottom.
- Wrong order? Drag a row by its grip, or focus the grip and press the arrow keys; the joined length and the seams follow.
- Leave Crossfade (s) at 0 for straight cuts, or type something like 1.5 to blend each clip into the next.
- Pick an output format. M4A is selected the first time; WAV, Opus and FLAC are the other three, and your pick is remembered.
- Press Join. It stays held until at least two clips are in the list. Play the joined track through its seams, then press Download.
About this tool
An audio joiner has one job: hand it several clips and get back one file that plays them end to end. Files merge top to bottom in the order the list shows them. Crossfade (s) sits at 0 by default, which gives you hard cuts between clips. Put a number in and each clip fades into the one after it over that many seconds.
Every clip decodes the moment it lands, so each row shows the filename next to its real running time, which is usually enough to spot the stray. Rows move by their grip: drag the dotted handle to where the clip belongs, or focus it and use the arrow keys. Remove drops one clip out of the queue without disturbing the rest, and a file the browser cannot decode never enters the list at all; a warning names it instead.
Output starts on M4A, with WAV, Opus, and FLAC beside it, and the joined length, every seam and the landing rate are stated before you press Join. A clip recorded at a different rate is resampled to the first clip's rate, and the page says which. Nothing downloads until you ask: the joined track plays on the page first, and Download saves it as joined with the extension of the format you picked.
Three songs, two seams, one mixtape
Take three MP3s at 3:41, 4:05 and 2:54, added in that order, with Crossfade (s) set to 2 and the format left on M4A. Straight addition promises 10:40 of audio. The two seams each swallow their overlap, so the joined file plays 10:36.
The strip says 10:36 before you press anything, and the two seams are marked on the track. Press Join and a bar follows the blend and the AAC encode; then the joined track plays in the same well, and the seam marks jump straight to 3:39 and 7:42 so you can decide whether two seconds was the right blend before you press Download for joined.m4a.
Good to know
- Every clip is decoded to raw samples and held in memory while the joined track is assembled, so a queue of hour-long files can run a phone out of room. The output takes its sample rate from the first clip in the list, and every other clip is resampled to it, so put the clip whose rate you want to keep first.
- A crossfade can only blend audio that exists. Ask for ten seconds of overlap going into a three-second sting and the blend runs three seconds, which is all the sting can give.
Frequently asked questions
Why isn't MP3 in the format list?
MP3 encoding needs a licensed encoder and I don't ship one. M4A is the closest swap: it carries AAC, plays on the same phones and car stereos MP3 does, and at matching quality the file usually comes out smaller.
How long should the crossfade be?
For music, somewhere between half a second and two seconds reads as a deliberate blend. For speech, stay under about 0.3 seconds or the words overlap and turn to mush. The field steps in tenths of a second.
Can I mix formats, an MP3 next to a WAV next to an m4a?
Whatever your browser can decode goes in the same list: MP3, WAV, M4A, OGG, FLAC. Anything that fails to decode gets skipped, and a warning names the file it dropped.
Does joining knock the quality down?
Each clip is decoded to raw samples first, then the whole thing is encoded once at the end. A lossy source picks up one more generation of encoding that way. Pick WAV or FLAC and the final step is lossless, which matters when the joined file is heading into an editor.
Why is the joined track shorter than my clips added together?
Crossfaded stretches play once, not twice. Every seam subtracts its overlap from the running total, so three two-minute clips with two-second fades land at 5:56 rather than 6:00. Set the crossfade back to 0 and the lengths add up exactly.
One clip is mono and the rest are stereo. What comes out?
The join is always stereo. A mono voice memo gets its single channel copied into both ears, so it sits dead centre between the stereo songs instead of leaning out of one side.
How many clips can the queue take?
No number is enforced; memory is the real wall. Decoded stereo at 44.1 kHz costs about 21 MB a minute while the join is being built, so an hour of material wants well over a gigabyte of headroom, and a phone taps out long before a desktop does.
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