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Audio looper.
A loop is bar-exact or it is broken.
Pick a section, pick a length in bars, and get it repeated as many times as you like with an equal-power crossfade over every seam. The loop points snap to a grid read off the track, and where they cannot, the tool tells you how many milliseconds off a bar you are and what that costs over the repeats.
Drop a track to loop
WAV, AIFF, FLAC, MP3 or M4A. One file at a time here, because a loop start is a position inside one particular arrangement. Nothing is uploaded — the file is decoded, changed and written back out in this tab.
The arithmetic nobody shows you
Forty milliseconds becomes a whole beat.
A loop error does not stay the size it started at. It accumulates, once per repeat, until it is audible.
Say you loop what looks like eight bars of a 128 BPM track by dragging in a waveform editor and you get it to within 40 milliseconds. That sounds like precision — it is a twenty-fifth of a second, far below anything you can consciously hear as a single event. Play it once and nobody would ever know.
Play it twenty-five times and you are a full beat out. The error does not average away, it adds: every repeat pushes the following one further from where the grid says it should be, so by the end of a two-minute loop the downbeat is landing on the two. If you built that loop to extend an intro so you could mix out of a long blend, the mix will fall apart in the last thirty seconds and it will not be obvious why.
This is why a DJ looper is a different tool from a general-purpose one, and it is only a different tool because it knows the tempo. Once the grid is there the loop points can snap to it, the length can be stated in bars, and the cases where it still cannot be exact — a track that speeds up, a live recording, anything without a steady pulse — can be reported honestly instead of silently passed on to you.
Points that snap to the grid, not to seconds
Set a loop in seconds and you will be wrong, because a bar at 127 BPM is 1.8898 seconds and nothing you type is going to be that. So the tempo is detected on drop, the bar lines are drawn over the waveform, and clicking anywhere on the picture puts the loop start on the nearest bar. Length is chosen in bars — 1, 2, 4, 8, 16, 32 — which is how loops actually get thought about, and the exact seconds are shown next to it.
Drift, in milliseconds, before you commit
When a loop cannot be made bar-exact the report says how far off it is and multiplies that by the repeat count. A loop 40 milliseconds short of a bar has drifted a full beat out of phase after 25 repeats, and if you did not know that in advance you find out when you try to mix into it. No general-purpose looper on the web reports this and it is the single most useful thing a looper can tell you.
An equal-power seam, so the level holds
Two correlated signals crossfaded on a straight ramp lose about 3 dB in the middle, which puts an audible dip on every join of a long loop — worse than the click it was meant to remove. The crossfade here is equal power, the same quarter-sine shape a mixer uses, so the level stays constant through the seam. And it is optional: a hard cut is genuinely cleaner when your loop points happen to land on a zero crossing, so the default is a butt join and the crossfade is there when you hear a click.
Loop lengths
What each length is for
Loop length is an arrangement decision. These are the ones that come up.
| Length | What it gives you | Typical use |
|---|---|---|
| 1 bar | A single phrase of the groove. | Isolating a drum pattern or a bassline figure, or making a short element to layer under something else. |
| 2 bars | The natural length of most house and techno loops. | The building block of the genre. Most tracks are built from two-bar loops and a two-bar loop of one will sound intentional. |
| 4 bars | A short section with a bit of variation in it. | Extending a groove without it becoming obviously repetitive. Long enough that a fill or a change lands inside it. |
| 8 bars | Half a phrase. | Extending an intro or an outro to give yourself more room to blend. The most common length for making a track easier to mix. |
| 16 bars | A full phrase. | A genuine arrangement section. Loop this and it reads as part of the track rather than as a loop. |
| 32 bars | Two phrases. | Turning a short edit into something with the length of a real record, or building a long bed to talk or mix over. |
The output length is shown as you change the repeats, so you can see that eight bars at 126 BPM repeated twelve times is three minutes and thirty seconds before you build it. Crossfading overlaps each copy with the previous one, so a crossfaded loop is very slightly shorter than the arithmetic suggests.
Frequently asked
Common questions
Why can I only loop one file at a time?+
Because a loop start is a position inside one particular arrangement. Bar 56 of one track is a completely different moment in another, so a batch looper would be a control that appears to work and quietly produces nonsense on every file after the first. The other processing tools here — the normaliser, the fade, the trimmer, the channel converters — all take a whole folder, because every setting they expose means the same thing on every file.
Does my file get uploaded?+
No. The file is decoded, looped and written back out inside your browser tab. There is no upload endpoint behind the page and it makes no network request once loaded.
How do I choose the loop start?+
Click the waveform. The click snaps to the nearest bar line when a tempo has been detected, so you cannot land between bars by accident. You can also type a time directly, and that gets snapped too. The shaded region on the waveform shows exactly what is going to be repeated.
What does "the loop is 40 ms off a bar" mean?+
It means the section you chose is not a whole number of bars long at the detected tempo. Every repeat therefore starts 40 milliseconds earlier or later than the grid expects, and the error accumulates — after 25 repeats you are a full beat out. If the number is under about three milliseconds the loop is exact for practical purposes; if it is large, either the tempo detection was wrong or the track does not have a steady tempo.
Should I use the crossfade?+
Only if you hear a click at the seam. A hard cut is the cleanest join when the loop points happen to fall at a zero crossing, which they often do on a rhythmic loop that starts on a kick. If you do hear a click, five milliseconds is usually enough and is completely inaudible as a fade. Longer crossfades soften the transient at the start of the loop, which is a real cost on a percussive loop.
Why is the crossfade equal power?+
Because the two things being crossfaded are highly correlated — they are the same audio. Two correlated signals faded across a straight ramp sum to less than either of them in the middle, about 3 dB down, so every seam would have a small dip in it. An equal-power curve keeps the total constant through the overlap, which is the same reason a mixer crossfader uses that shape.
Can I use this to extend a track for mixing?+
That is the main reason to reach for it. A track with a four-bar intro is hard to mix into; loop those four bars three or four times and you have sixteen bars of room. The same applies to an outro that stops too abruptly. Because the loop is bar-exact the extended version beat-matches exactly like the original, and your DJ software will grid it the same way.
What if no tempo is detected?+
The bar snapping and the bar-length buttons disappear and you set the points in seconds instead. Everything still works, you just lose the guarantee — and the report says so rather than implying a precision it cannot deliver. This happens on ambient material, live recordings and anything without a steady pulse.
How many repeats can I make?+
Up to 200, which on an eight-bar loop at 128 BPM is about eighty minutes. The practical limit is memory rather than the number — a very long output at 24-bit stereo is a large file, and the size is shown on the download button before you save it.
Can I hear it before downloading?+
Yes. A player appears with the finished loop as soon as it is built, so you can check the seam and the drift with your ears rather than trusting the numbers. Nothing is saved until you press download.
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