When browsing videos on Youtube.com, users may receive the following exception page:
YouTube has introduced support for Brotli encoding, which is not supported by the ProxySG at this time (April 6, 2017). See this Wikipedia entry to learn more about Brotli encoding.
Because SGOS does not understand Brotli encoding, you will need to disable support for it. There are two options for this: modify the client browser, or install policy on the Proxy.
Disable Brotli Encoding Support in Google Chrome
Disable Brotli Encoding Support in Mozilla Firefox
Alternatively, you can disable support for Brotli encoding just for YouTube in policy on the Proxy: