
webNBT - Web-based - If just need to toggle a flag or two and don't want the hassle of installing an application, WebNBT will get the job done.It also supports Minecraft Bedrock NBT files. NBT Studio - Windows - It looks similar to NBTExplorer and is the spiritual successor of the previous app, but it is a total rewrite with frequent updates.
We're including it here for posterity and as a backup option if you need it. Great program, but hasn't been updated since 2017.
NBTExplorer - Windows (MacOS and Linux compatible with Mono runtimes) - One of the original Minecraft NBT editing tools. For the purposes of this tutorial, we're using NBT Studio on a Windows PC, but we'll list other options here in case you're using a different operating system or don't want to install an app at all. To edit the level.dat and related files without corrupting them, we'll need to use one of the available Minecraft-friendly NBT editors to do so. Let's look at two techniques you can use to change the game modes: first a temporary one for those times you need a quick fix, and then a permanent one. Whatever your motivation for changing the world type, it's a pretty straightforward process. Or perhaps you're doing so well in your hardcore mode world that you're now anxious at the thought of losing it should you die. Or perhaps you want to start in creative mode to build your home base and then switch to survival mode to take on the world from the comfort of your freshly built castle. Minecraft lends itself to creativity and changing playstyles, however, and you may find that the map you intended to make a creative map feels like it would be a perfect survival map or vice versa. Under normal circumstances, this selection is fixed, and a permanent flag is set within the world file. You can choose from creative, survival, and hardcore modes.
When you create a new world, you select your game mode. Why Change Between Survival, Creative, and Hardcore?