There has been a long-standing issue with video downloads in Telegram.
When a video starts downloading and the user cancels or stops the download, the download appears to stop in the UI. However, in some cases, the download continues silently in the background.
After several hours, the user may discover that the video has been completely downloaded despite having cancelled the download earlier. This can consume a significant amount of mobile data, battery, and storage without the user's knowledge.
There is also a related issue with videos that are available in multiple quality options. For example, if a video is available in three or four different qualities and the user selects a lower-quality version to watch or download, Telegram may eventually download multiple or even all available quality versions in the background.
As a result, significantly more data and storage space can be consumed than the user intended.
The download should stop completely when the user cancels it, and only the quality explicitly selected by the user should be downloaded.
Steps to reproduce
Open Telegram on an Android device.
Open a chat, group, or channel containing a video.
Start downloading a video.
While the video is downloading, cancel or stop the download.
Verify that the download indicator appears to have stopped.
Leave Telegram running or in the background for an extended period of time.
After some time, check the downloaded files or Telegram's storage usage.
In some cases, the video will have continued downloading and will eventually be fully downloaded despite the cancellation.
Additional scenario — Multiple video qualities
Open a video that is available in multiple quality options, such as 360p, 480p, 720p, and 1080p.
Select or start playing the video in a lower quality.
Stop or cancel the download if necessary.
Leave Telegram running for some time.
Check the device's storage usage or Telegram's downloaded media.
Multiple quality versions of the same video may have been downloaded, even though the user only intended to watch or download one specific quality.