High Sierra Mac 2011 video

The version of Firefox that Mozilla distributes for High Sierra is an older version – Firefox 115 ESR. It hasn't gotten new features in some time. It was supposed to stop getting "critical security updates" last September or October, but Mozilla gave it a reprieve, and now it is scheduled to stop getting them in March.

I do not know if Firefox 115 ESR is enough to view current Internet videos.

Servant of Cats wrote:

I do not know if Firefox 115 ESR is enough to view current Internet videos.

I have no problems viewing streaming video on my MBP running High Sierra with Firefox ESR 115.

115.20.0 is the latest release (Feb 7, 2025)

ESR releases are available here -> https://www.mozilla.org/en-US/firefox/all/desktop-esr/

Do you mean ALL video? What about saved videos on your Mac? Have you tried YouTube? What about video adverts, e.g. in Facebook?

I use a 2011 iMac and can play all video even in Mavericks (except DRM, where I have to use a High Sierra VM).

lol likely not flash players

if it was me then I would try looking for firefox they support older macOS version

Download Mozilla Firefox for Mac — Fast, Private & Free - from Mozilla

FYI, Adobe discontinued Flash Player on December 31, 2020. They actively blocked content from running in the latest versions of Flash Player starting on January 12, 2021.