I see that link embeds here, but not on my forum, what setting to embed .mp4 links?
https://i.imgur.com/00jwOpb.mp4
סיכום מבוסס בינה מלאכותית
User danielabc reported that .mp4 links (e.g., from Imgur) do not embed on their Discourse forum, despite working elsewhere. Canapin tested the same link on a fresh Discourse install and confirmed it embeds correctly, suggesting the issue may be configuration-related. JammyDodger advised checking the authorized extensions setting to ensure .mp4 is still permitted — danielabc confirmed it is set to mp4 but the issue persists. Canapin expressed uncertainty about the cause. Later, Canapin retested on danielabc’s forum and found the embed now works, prompting a request for clarification on whether the issue is resolved and what (if anything) was changed. danielabc also briefly asked if Discourse can be installed from scratch without member accounts — unrelated to the embed issue. No definitive fix was identified, but the problem appears to have resolved itself or was corrected outside the thread.
You could check authorized extensions to make sure you’ve not removed it at some point?
it’s set to mp4 but it doesn’t work
Well, unfortunately I have no idea. 
is there an option to install speech from scratch without members account?
