I saw that mirc cannot open that link "https://mircscripts.net/snippets/project[RtX3K].jpg" that is valid, not even changing the mouse cursor as pointer when moving up on it.

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That is not a valid URL. It may work, but the official standard requires that those square brackets be encoded (as %5B and %5D) instead. As you can see, this forum also does not recognize your full URL as valid.

Brackets in URL are only allowd for IPv6-Adresses in the Host-Part, ex. https://[IPv6]:8080/sub