This is the most frequent issue. Because many of these games use direct peer-to-peer WebRTC, your firewall might be blocking the connection.
For the community, the extension is a badge of honor. It signifies that the project is likely open-source, community-driven, or hosted in a way that prioritizes accessibility over monetization. 1v1 githubio
"I can't find the 1v1 button." Solution: Many GitHub pages are portfolios first, games second. Look for a menu or a "Play Now" modal. If you see code text, you are on the wrong page (the repository view). You need the raw or index.html live page. 1v1 GitHub Pages: A Comprehensive Write-up This is