# YouTube and WebM/AV1

YouTube’s content above 1080p is only available in WebM or AV1 video formats. These downloads are then placed in files with `.webm` and `.mkv` extensions, do not play in QuickTime Player and require a 3rd party player (VLC, Elmedia Player, …). The `.webm` file may have an icon of your browser (Chrome, Firefox, …) as these browsers can handle these formats.

If you want the downloaded file to be an MP4 file, there are several solutions:

- if you want the full resolution, set postprocessing to MP4, though please note that re-encoding video at 4K resolution can take considerable amount of time. See postprocessing help for more information.
- go to Preferences > General and limit the quality to 1080p. Most videos on YouTube offer a 1080p rendition in MP4 and Downie will select it. In combination with the postprocessing set to MP4 (see above), you will always end up with an MP4 file and as the resolution is lower, the conversion will take less time than in case of 4K video.
- go to Preferences > General and enable the “Force MP4 Format” option which will force Downie to select an MP4 rendition even though it’s not the highest resolution available. Example: a video is offered at 4K in WebM, 1080p in WebM and 720p in MP4 - Downie will select the 720p download in MP4.