SEE MY NEW, MORE ADVANCED FIRE TWEAKING MOD, "CONTROLLED BURN" HERE:
If "No Fire Spread" acts exactly as you want though, then great! But if you want more detailed control over fire behavior, go to the link above!
Ever wanted to prevent massive server lag from forest fires? Or maybe just keep your netherrack fireplace (enclosed in cobble) from lighting up your wooden house?
Don't like how the "/gamerule doFireTick false" command also stops fires from destroying blocks or being extinguished naturally?
Well, when installed, this mod prevents fire from spreading more fire, WITHOUT the unnecessary features of the related gamerule command.
Fire can still be created by all other sources (flint and steel, lava, ghast fireballs) but will not spread further after being set (it may seem to from eg. lava but that's just the lava itself causing fires).
Fire still breaks blocks! On this note, keep in mind that fire has the ability to break any flammable block adjacent to it (not just the one below the fire).
I created this mod for my own use, in a modpack that includes "Better with Mods", which requires the ability to set fires under cauldrons, kilns, etc. I did not want "eternal fire" on the logs under my cauldron (because that breaks game balance) and I did not want fire to spread (due to eg. forest fires causing massive server lag). By these factors combined(!) I could not solve the issue with the vanilla server properties, and did not find a suitable mod on this site, so I made one.
Yes, you can use it in your modpack if you want (MIT license).
A list of my curseforge mods can be found here