August 19, 2022

Microsoft’s xCloud game streaming appears to dip to a lower visual quality setting when running on Linux. The apparent downgrade across operating systems was noted by a Reddit user over the holiday weekend and confirmed in Ars’ testing this morning.

To compare how xCloud handles a Linux machine vs. a Windows machine, an Edge extension was used during testing to force the browser’s User-Agent string to present itself as a Linux browser:

  • Windows User-Agent tested: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.5060.66 Safari/537.36 Edg/103.0.1264.44
  • Linux User-Agent tested: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/102.0.5005.27 Safari/537.36 Edg/102.0.1245.7

Tests were conducted on the latest version of Microsoft Edge (Version 103.0.1264.44, 64-bit) running on a Windows 10 PC. All tests were run on a wired Internet connection registering download speeds of 120 Mbps and ~9 ms latency, according to spot tests at Fast.com.

A GIF comparing one corner of the image in two xCloud-streamed sessions, with only the User-Agent string changing between them.

The difference in streaming quality can be seen in the above gallery (expand images to full screen for a better view). With the Linux User-Agent, edges are generally less sharp and colors are a little more washed out. The difference is even more apparent if you zoom in on the Forza logo and menu text, which shows a significant reduction in clarity.

What’s going on here?

Interestingly, the dip in quality seems to go away if you enable “Clarity Boost, an Edge-exclusive feature that “provid[es] the optimal look and feel while playing Xbox games from the cloud,” according to Microsoft. That’s great for Linux users who switched over to Microsoft Edge when it launched on Linux last November. But Linux users who stick with Firefox, Chrome, or other browsers are currently stuck with apparently reduced streaming quality.

That Linux quality dip has led some to speculate that Microsoft is trying to reserve the best xCloud streaming performance for Windows machines in an attempt to attract more users to its own operating system. But using a Macintosh User-Agent string provides streaming performance similar to that on Windows, which would seem to be a big omission if that theory were true. Microsoft also hasn’t published any kind of “best on Windows”-style marketing in promoting xCloud streaming, which would seemingly be a key component of trying to attract new Windows users.

(The quality difference could be a roundabout attempt to get Linux users to switch to the Edge browser, where Clarity Boost offers the best possible quality. But that still wouldn’t fully explain why Windows users on other browsers, without Clarity Boost, also get better streaming quality than their Linux brethren.)

Others have suggested that the downgrade could simply be a bug caused by Microsoft’s naive parsing of the User-Agent strings. That’s because the User-Agent strings for Android browsers generally identify themselves as some version of Linux (“Linux; Android 11; HD1905,” for example). Microsoft’s xCloud code might simply see the “Linux” in that string, assume the user is running Android, then automatically throttle the streaming quality to account for the (presumably) reduced screen size of an Android phone or tablet.

With Microsoft declining to comment to Ars Technica, we’re still stuck theorizing what’s behind this apparent issue. For the time being, though, Linux users who want the best xCloud performance will want to switch over to Microsoft Edge with Clarity Boost or at least fake their User-Agent settings to pretend they’re running Windows.

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