Twitch

Authentication

Official authentication support for Twitch via the --twitch-oauth-token and --twitch-oauth-authenticate CLI arguments had to be disabled in Streamlink's 1.3.0 release in November 2019 and both arguments were finally removed in the 2.0.0 release in December 2020 due to restrictive changes on Twitch's private REST API which prevented proper authentication flows from third party applications like Streamlink.

The issue was that authentication data generated from third party applications could not be sent while acquiring streaming access tokens which are required for watching streams. Only authentication data generated by Twitch's website was accepted by the Twitch API. Later on in January 2021, Twitch moved the respective API endpoints to their GraphQL API which was already in use by their website for several years and shut down the old, private REST API.

This means that authentication data, aka. the "OAuth token", needs to be read from the web browser after logging in on Twitch's website and it then needs to be set as a certain request header on these API endpoints. This unfortunately can't be automated easily by applications like Streamlink, so a new authentication feature was never implemented.

In order to get the personal OAuth token from Twitch's website which identifies your account, open Twitch.tv in your web browser and after a successful login, open the developer tools by pressing F12 or CTRL+SHIFT+I. Then navigate to the "Console" tab or its equivalent of your web browser and execute the following JavaScript snippet, which reads the value of the auth-token cookie, if it exists:

document.cookie.split("; ").find(item=>item.startsWith("auth-token="))?.split("=")[1]

Copy the resulting string consisting of 30 alphanumerical characters without any quotations.

The final Authentication header which will identify your account while requesting a streaming access token can then be set via Streamlink's --http-header or --twitch-api-header CLI arguments. The former will set the header on any HTTP request made by Streamlink, even HLS Streams, while the latter will only do that on Twitch API requests, which is what should be done when authenticating and which is the reason why this CLI argument was added.

The value of the Authentication header must be in the format of OAuth YOUR_TOKEN. Notice the space character in the argument value, which requires quotation on command line shells:

$ streamlink "--twitch-api-header=Authentication=OAuth abcdefghijklmnopqrstuvwxyz0123" twitch.tv/CHANNEL best

The entire argument can optionally be added to Streamlink's (Twitch plugin specific) config file, which doesn't require quotes:

twitch-api-header=Authentication=OAuth abcdefghijklmnopqrstuvwxyz0123

Embedded ads

In 2019, Twitch has started sporadically embedding ads directly into streams in addition to their regular advertisement program on their website which can only overlay ads. The embedded ads situation has been an ongoing thing since then and has been turned off and on several times throughout the months and years, also with variations between regions, and it has recently been pushed more and more aggressively with long pre-roll ads.

While this may be an annoyance for end-users who are used to using ad-blocker extensions in their web-browsers for blocking regular overlaying ads, applications like Streamlink face another problem, namely stream discontinuities when there's a transition between an ad and the regular stream content or another follow-up ad.

Since Streamlink does only output a single progressive stream from reading Twitch's segmented HLS stream, ads can cause issues in certain players, as the output is not a cohesively encoded stream of audio and video data anymore during an ad transition. One of the problematic players is VLC, which is known to crash during these stream discontinuities in certain cases.

Unfortunately, entirely preventing embedded ads is not possible unless a loophole on Twitch gets discovered which can be exploited. This has been the case a couple of times now and ad-workarounds have been implemented in Streamlink (see #3210) and various ad-blockers, but the solutions did only last for a couple of weeks or even days until Twitch patched these exploits.

To filter out ads and to prevent stream discontinuities in Streamlink's output, the --twitch-disable-ads argument was introduced in Streamlink 1.1.0 in 2019, which filters out advertisement segments from Twitch's HLS streams and pauses the stream output until regular content becomes available again. The filtering logic has seen several iterations since then, with the latest big overhaul in Streamlink 1.7.0 in 2020.

In addition to that, special API request headers can be set via --twitch-api-header that can prevent ads from being embedded into the stream, either authentication data or other data discovered by the community.

Low latency streaming

Low latency streaming on Twitch can be enabled by setting the --twitch-low-latency argument and (optionally) configuring the player via --player-args and reducing its own buffer to a bare minimum.

Setting --twitch-low-latency will make Streamlink prefetch future HLS segments that are included in the HLS playlist and which can be requested ahead of time. As soon as content becomes available, Streamlink can download it without having to waste time on waiting for another HLS playlist refresh that might include new segments.

In addition to that, --twitch-low-latency also reduces --hls-live-edge to a value of at most 2, and it also sets the --hls-segment-stream-data argument.

--hls-live-edge defines how many HLS segments Streamlink should stay behind the stream's live edge, so that it can refresh playlists and download segments in time without causing buffering. Setting the value to 1 is not advised due to how prefetching works.

--hls-segment-stream-data lets Streamlink write the content of in-progress segment downloads to the output buffer instead waiting for the entire segment to complete first before data gets written. Since HLS segments on Twitch have a playback duration of 2 seconds for most streams, this further reduces output delay.

Note

Low latency streams have to be enabled by the broadcasters on Twitch themselves. Regular streams can cause buffering issues with this option enabled due to the reduced --hls-live-edge value.

Unfortunately, there is no way to check whether a channel is streaming in low-latency mode before accessing the stream.

Player buffer tweaks

Since players do have their own input buffer, depending on how much data the player wants to keep in its buffer before it starts playing the stream, this can cause an unnecessary delay while trying to watch low latency streams. Player buffer sizes should therefore be tweaked via the --player-args CLI argument or via the player's configuration options.

The delay introduced by the player depends on the stream's bitrate and how much data is necessary to allow for a smooth playback without causing any stuttering, e.g. when running out out available data.

Please refer to the player's own documentation for the available options.