Audio Fade In and Fade Out

About this tool

Choose an audio file (or a video, from which the sound is taken), set how many seconds the fade-in at the start and the fade-out at the end should last, and choose the format to save in: MP3, M4A (AAC) or WAV. The fades use ffmpeg's afade filter, a smooth change of the volume from silence to full at the start and back at the end. The two fades together cannot be longer than the audio, and you are told if they are. We measured the result of a test tone: the level in the first 50 milliseconds and the last 50 milliseconds was below 15 percent of the level in the middle, for all three formats, and the length was unchanged. We checked the ffmpeg commands this tool builds by running them with a real ffmpeg on test clips and measuring the results (sizes with ffprobe, picture content with ImageMagick, sound with a spectrum and loudness meter), and the page itself in a browser with the real ffmpeg.wasm engine. The first use downloads the ffmpeg engine (about 25 MB), which then stays in your browser cache. It needs a current desktop Chrome, Edge or Firefox; large videos use a lot of memory, and very long clips can fail on small devices. Your file is processed in your browser with ffmpeg and never uploaded.

How to use it

1. Choose an audio file.
2. Set the fade-in and fade-out times.
3. Choose the format and press Process.
4. Download the file.

Common problems

It says the fades are longer than the audio

Make the two times add up to less than the length of the file.

The result is a different format

Choose the format in Save as. MP3 and M4A are compressed, so they are smaller than WAV.

The start is still loud

Set a fade-in of at least a second. A fade of 0 seconds does nothing.