Add a fade in and fade out to any audio file

How to use the fade tool

1. Add an audio file. Common formats such as MP3, M4A, WAV, OGG and FLAC, plus the sound from MP4 or MOV video, are accepted.
2. Enter Fade in and Fade out in seconds (defaults 2 and 3, steps of 0.1).
3. Pick a Curve: Linear, Exponential (smooth), Logarithmic (fast) or Equal power.
4. Choose Save as and, for M4A, WebM or OGG, a Bitrate. Press Apply fades and download the result.

What it does and when to use it

A hard start or a sudden stop sounds like a mistake. Fades fix that for music cut from a longer track, background beds under a video, podcast intros and outros, and phone recordings that begin with a bump. A short fade of 0.1–0.5 s is enough to remove a click at a cut; 2–8 s gives the familiar end-of-song fade.

If you still need to choose the section, cut it with the audio trimmer first, which adds tiny anti-click fades at its cuts but not musical ones. For a ringtone, the ringtone maker trims and fades in one step. To join two pieces with an overlap, use the crossfade in the audio merger.

How it works

The audio is decoded in a Web Worker on your device. Each sample in the fade-in region is multiplied by a gain that rises from 0 to 1; the fade-out is the mirror image, falling to 0 at the last sample. With t running from 0 to 1 across the fade:

• Linear: gain = t
• Exponential: gain = t³ (slow start)
• Logarithmic: gain = 1 − (1 − t)³ (fast start)
• Equal power: gain = sin(t × 90°)

If fade in + fade out is longer than the file, both are multiplied by duration ÷ (fade in + fade out). The middle of the file is not changed.

Worked examples

From the tool’s own output:

• A 60-second song, Fade in 2, Fade out 3, Exponential: Fade in 2 s, Fade out 3 s, Length 1:00.00, saved as song-faded.wav (5 MB as 16-bit mono WAV).
• A 4-second jingle with the same settings: the 5 s of fades do not fit, so the result reports Fade in 1.6 s and Fade out 2.4 s.

Limits and tips

• Fades work on the whole file only. For a fade in the middle (a dip under speech), use an editor with volume automation.
• Exponential fade-outs reach near-silence earlier than linear ones, so a 3 s exponential fade can feel shorter. Lengthen it if the end feels abrupt.
• The output is a new encode. Saving a faded MP3 as M4A or OGG adds a second round of lossy compression; WAV avoids that.
• Non-WAV input relies on your browser’s WebCodecs decoder; AIFF, AMR, WMA and CAF need the optional ffmpeg fallback (about 30 MB, downloaded once from cdn.jsdelivr.net). Long files on a phone may run out of memory, since the whole track is decoded first.