Fade In/Out softens the beginning and the end of a video or audio file: the opening brightens up from black, the closing frame goes dark as the sound fades away, or a stretch of background music gets a few seconds of fade so it hands over to the next track. It is the “Fade in/out” tab of the audio/video workbench.

A video file has its picture and sound handled together: the picture fades in from black and out to black with the fade filter, while the audio rises and falls in sync with afade, both on exactly the same timings, and the output is re-encoded as MP4 (H.264 CRF 20 + AAC 128 kbps). An audio-only file gets afade alone and keeps its original format (WMA, AMR and the like become MP3). The start of the fade-out is calculated as total duration − fade-out length, so the file's duration has to be detected first.

1. 01Add a file and select it— video or audio — and switch to the “Fade in/out” tab.
2. 02Set the lengths— drag the “Fade-in length” and “Fade-out length” sliders (0–10 seconds, 0.5 steps, both 1.5 seconds by default); for a fade-out only, drag the fade-in to 0.
3. 03Read the warnings— if the two add up to more than the file's total length a warning appears and the button is disabled; when the duration has not been detected the fade-out will not apply and the panel says so.
4. 04Apply and download— click “Apply fade in/out” and download <original-name>_fade.mp4, or the matching audio file, when it finishes.

Start and end only

— the fade-in always begins at 0 seconds and the fade-out always runs to the end; a gradient cannot be inserted somewhere in the middle and there is no cross-fade between two sections

One colour

— picture fades only go to black, not to white or any other colour

Video is re-encoded

— the whole clip is re-encoded as H.264 CRF 20 and always output as MP4, taking time in proportion to its length; AV1 sources cannot be decoded; a video without an audio track only has its picture processed

It needs duration information

— the fade-out needs to know the total length, and a file whose duration cannot be detected can only be faded in

What it does not do

— it does not cut extra material at the head or tail (use Trim and Cut Video Clips), adjust the overall volume (use Volume Adjust) or join several sections (use Video Merge)

Processing happens locally in the browser through ffmpeg.wasm and the file is not uploaded; the first use downloads about 31 MB of engine from a CDN (the site's asset domain or jsDelivr) and that request contains none of your file.