Fade audio in and out

How to fade audio in and out

1. 1

   Add your audio file

   MP3, WAV, FLAC, M4A, AAC, OGG or Opus, up to 200 MB per file; up to twenty files get the same fades in one go.

2. 2

   Set the fade-in and fade-out durations

   Either can be zero if you only want one of them. Each side gets its own curve shape.

3. 3

   Click Apply and download

   The result is a WAV with smooth edges and everything between them untouched.

How the three curve shapes actually sound

A linear fade moves the level in a straight line, which sounds slightly abrupt at the quiet end, because human hearing is logarithmic, so equal steps in amplitude are not equal steps in perceived loudness. Logarithmic rises quickly at first and then flattens out, which is the shape most people describe as a natural fade and the one to reach for when you just want the music to arrive. Exponential does the opposite: it holds near silence for longer and then climbs, which is useful for a slow reveal or when the opening of the track is already loud and a linear fade would make it jump in. The differences are small on a one-second fade and obvious on a ten-second one.

One side or both

Setting either duration to zero switches that side off, so a fade-in with no fade-out or a fade-out with no fade-in are both a single setting away. Setting both to zero leaves nothing to do, and the tool says so instead of handing back a copy of the original and letting you wonder whether it worked. That refusal also applies when the tool is reached through the pipeline from another page, where there is no form to stop you first.

When the fades are longer than the file

Asking for a ten-second fade-in and a ten-second fade-out on a fifteen-second clip is a contradiction, and there are two sensible ways to resolve it. This tool shrinks both durations proportionally until they fit inside ninety per cent of the file, keeps the ratio you asked for, and tells you the numbers it used. Proportional matters: if you asked for a short opening and a long tail, you still get a short opening and a long tail, just scaled down. The alternative, clipping both to the same value, would quietly change what you asked for.

Where the fade windows overlap

When the two fades nearly meet, their gain curves are multiplied together rather than one replacing the other. The difference shows up exactly at the meeting point: replacement produces a step in the level, and a step in level is a click. Multiplying keeps the curve continuous, so a file where the fade-in runs straight into the fade-out swells and falls away without a seam.

Frequently asked questions