Implementations disclose zero-copy adaptive bitrate video streaming. A method includes capturing, by a user device, a first video frame of a plurality of video frames of a video item to be transmitted as a livestream; delivering the first video frame to an encoder of the user device; capturing a second video frame of the plurality of video frames, the second video frame being captured after the first video frame; delivering the second video frame to the encoder of the user device; in response to determining that the first video frame did not enter the encoder prior to the second video frame arriving at the encoder, discarding the first video frame; determining, by the user device, a frequency of discarded video frames comprising the first video frame; and adjusting, by a processing device of the user device, quality of the video item transmitted as the livestream based on the frequency.