XPost: alt.comp.software.firefox   
   From: mariasophia@comprehension.com   
      
   Lawrence DÿOliveiro wrote:   
   > On Sun, 1 Feb 2026 09:52:58 -0500, Maria Sophia wrote:   
   >   
   >> I'm glad Lawrence D'Oliveiro and others (like Carlos) were   
   >> successful with deno and node ...   
   >   
   > Actually, Iÿm not sure my yt-dlp installation is using any actual   
   > JavaScript engine (yet). I was getting ´403 Forbidden¡ errors a week   
   > or two back, but that went away after a newer update.   
      
   Months ago we covered the YouTube login challenge which was similar in that   
   every person had a different situation when it came to reproducing results.   
      
   This is the classic YMMV case since results depend on YouTube algorithms.   
      
   1. These are possible reasons why yt-dlp might work without a JS engine   
      A. YouTube does not apply its JS proof-of-origin checks to all users.   
         Some regions, IP ranges or accounts do not receive the challenge.   
      B. yt-dlp can still use older extraction paths when the JS challenge   
         is not triggered. These include cached signatures and older logic.   
      C. A recent yt-dlp update may have added new extraction patterns that   
         temporarily bypass the need for a JS engine.   
      D. YouTube sometimes rolls back new anti-bot code when it causes   
         problems. If that happened in your region, extraction may work   
         again without JS.   
      E. Not all videos require JS-based signature checks. Older videos or   
         videos on certain CDNs may still work with pure Python logic.   
      
   2. What this means   
      A. yt-dlp can appear to work normally even when no JS engine is   
         installed.   
      B. This does not mean the new JS requirement is gone. It only means   
         our requests have not triggered the new challenge recently.   
      C. The yt-dlp developers have stated that a JS runtime will become   
         necessary for reliable long-term YouTube extraction.   
      
   3. Summary   
      A. Your system has not hit the new challenge again yet.   
      B. Because the requirement is real and will return.   
      C. Installing a JS engine such as deno.exe remains the long-term fix.   
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