How to Add Fade In and Fade Out to Any Audio File

To add fade in and fade out to an audio file, open Zro7 Audio Fade, drop your file, and set the fade-in and fade-out durations in seconds. Zro7 writes an afade filter chain into ffmpeg.wasm and re-encodes locally — no upload, no signup, no watermark. Cleaner than Audacity for a one-off, more private than any online audio editor.

What a fade actually is

A fade multiplies each audio sample by a gain curve that ramps from 0 → 1 (fade in) or 1 → 0 (fade out). The default curve in FFmpeg is a cubic ease, which sounds smoother than a straight line and avoids the audible click you get when audio starts or ends at full volume.

Steps

1. Open Audio Fade.
2. Drop an MP3, WAV, M4A, OGG, or FLAC file.
3. Enter fade-in seconds (e.g. 2) and fade-out seconds (e.g. 3).
4. Preview, then export.

How Zro7 does it

• afade=t=in:st=0:d=2 — 2-second fade starting at t=0.
• afade=t=out:st=DURATION-3:d=3 — 3-second fade ending at the last sample.
• Curve is cubic by default — smoother than linear, no clicks.
• Re-encoded once through libmp3lame / libopus / aac depending on target format.

Common fade lengths

• Podcast intro/outro: 1–2 seconds.
• Music track outro: 4–8 seconds.
• Notification sound: 0.05–0.15 seconds — just enough to kill the click.