Forum software usually resizes anyway, give one a try and see if it can cope with the size.

The forum resizes but it took a while for big photos to chug across the internet when I had a slow internet connection. (8Mb/s down/1.0Mb/s up) To avoid timeout errors I either set the camera to 1024×640 or resized big photos myself with gimp or Imagemajick before transmission. (Other editors available!)

No problem with timeouts now my broadband is 12Mb/s up, so I just send whatever is in the camera and let the forum sort it for me.

Not clear how the forum decides resize values. Many of mine have been crunched down to 150×113 pixels, others are 500×667, and there are a few oddities like '1280×960 scaled to 640×480'.

If a detailed photo needs to be fully zoomable, best to store the jpg on another website and link to it with the Image button. There is no size limit unless the other website has one.

Dave