I've discovered a temporary work-around for those having memory issues with UDL as GM. Test this yourself on a copy of your dungeon, use at your own risk, etc. I'm running Dungeon of the Mad Mage and am on Level 3, which is huge. We switched from LDL with Advanced Fog of War to UDL with Explorer Mode due to the high lag with LDL for the players. After the players had explored for a session and mapped a bunch of it out, and we quit, then I later reconnected, I found that my browser tab (latest Chrome or Firefox, Windows 10, 16GB, 1080ti) would "Awe Snap!" with an Error code: SBOX_FATAL_MEMORY_EXCEEDED. It was just hours before our next session, so in my rush to get things working I "upgraded" one of my backup copies of the dungeon to current events, copied over all scripts, etc., gave the players a new URL, and told them that this was going to be the dungeon we would use from now on. After that session was over, I quit and rejoined and I got the SBOX_FATAL_MEMORY_EXCEEDED error again! I spent a few hours tinkering and discovered that it seems to be related to Explorer Mode. The following work-around allows me to load the map again with little effort/time. I will reference "level 3" as my high memory map: Start to load the dungeon as GM, then immediately click the Page Toolbar and switch to the Start/Landing page rather than finish loading level 3. Log out and close/open the browser and log in. Drag the Players Ribbon to the start page as well (if you don't and they are logged in the next steps can reveal the entire map to them). Click the Page Toolbar, go to settings for level 3, Dynamic Lighting tab, turn off Explorer Mode. This doesn't seem to zero out previously seen portions of the map, it just stops adding new areas. Then switch yourself as GM to level 3 and you can load it without any memory errors! Once you are on level 3, you can re-enable Explorer mode and memory use will not go through the roof. Drag the players ribbon to level 3 as well and the players can join normally and can still see areas they had previously explored. Play your session! Once you exit the game and re-join, the memory use will go through the roof again... So before leaving, switch yourself and the players to the Start/Landing page to make it easier to repeat this process next time. This has saved me considerable pain. I hope it helps someone else! Hopefully the memory bug will be fixed soon and we won't have to do this for long.