I've been trying to search for an answer to this question for some time now
(World Load Detection / Chunk Load Detection / Join World / etc)

However, despite my effort, I've been unable to find a solution...


  • This is a single-player world, NOT a private or public server
  • The use of command blocks is acceptable
  • It needs to activate when I open the world, but only once
    • (and every time the save is loaded, but only once)
  • It is a 1.15 save file

I found a lead on this reddit post: https://www.reddit.com/r/technicalminecraft/comments/7vr2gz/worldchunk_loaded_detector/

This also seemed promising but I couldn't quite follow...

However, the solution appears to be outdated (1+ year ago) and no longer works in version 1.15

Does anyone have any ideas?

I've tried the /tag and /scoreboard approach but those only seem to work on servers (local or public) since the command blocks will be running regardless of players being on the server
With this being a local save (and not a server), that does not appear to work.

  • What exactly is that question? – Joachim Jan 31 '20 at 14:15
  • Using redstone, is it possible to detect the load of a world... (with or without the use of command blocks) – JoeBro Jan 31 '20 at 14:20
  • Why are you adding the restriction of requiring the use of redstone? It might be the case that redstone is required, but that isn't reason enough to artificially restrict possible solutions. – MBraedley Jan 31 '20 at 15:27
  • What would be the alternative? – JoeBro Jan 31 '20 at 18:14
  • The alternative is to just not use redstone, and for commands, you shouldn't be using redstone anyway. – MBraedley Jan 31 '20 at 19:35

With commands it's easy:

/scoreboard objectives add leave custom:leaveGame

This ticks up once for every time you leave the world, so it can be detected on the next server tick (when you have joined again). I do not know how it behaves when Minecraft is killed or crashes.

Example usage:

/execute if entity @a[scores={leave=1..}] run say The world was reopened.
/scoreboard players reset * leave
  • "/scoreboard objectives add leave leaveGame" >> "unknown criteria 'leaveGame' " – JoeBro Jan 31 '20 at 18:16
  • Oh sorry, I forgot "custom:". Some special scoreboard types have that, some don't, seemingly randomly. – Fabian Röling Jan 31 '20 at 18:46
  • /scoreboard objectives add leave minecraft.custom:minecraft.leave_game "DISPLAYNAME" (For 1.15) Thanks for the update! I'm trying to implement this into my world now, I'll update my post with setup and accept after I get it working. – JoeBro Feb 1 '20 at 6:41
  • minecraft: is optional, as well as the display name, which is only displayed in the sidebar if you make your scoreboard visible there. – Fabian Röling Feb 1 '20 at 12:45
  • No, don't put the answer into your question, it's called "question" for a reason. – Fabian Röling Feb 1 '20 at 12:46

I showed this question to some experts about the limits of what redstone can do, but they didn't respond. :(
So I found a solution myself: My initial idea was that chunk loading detectors might work as world loading detectors as well. It turns out that this is true, even when you close and re-open the world inside the chunk with the detector inside it. So you just need to put one of those detectors e.g. every 320 blocks in both X and Z direction for render distance 10 and somehow get the output to where you want it.

Now the problem of building a chunk loading detector. I found a very easy one on Reddit, which works in 1.15.2 as well: https://www.reddit.com/r/technicalminecraft/comments/7vr2gz/worldchunk_loaded_detector/

Here is an image. Everything is self-explanatory, except this: The armour stand wears frost walker boots.

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