Short answer: reverse conversion is not supported

TopoBlocks’s edition conversion is one-way, Java Edition to Bedrock. A Bedrock world cannot be converted back to Java Edition—this isn’t us being lazy, it’s because the two editions use fundamentally different world formats: Java stores data in region/.mca (NBT), while Bedrock uses db/ (LevelDB). We only offer a verified Java Edition to Bedrock conversion with a compatibility score, and we won’t pretend we can do Bedrock to Java. If you want to understand the differences first, see What’s the difference between Java Edition and Bedrock.

How do I play with Java Edition players?

  • Have everyone switch to Bedrock (recommended). If that map started as a Java world, use Java to Bedrock (playable on iPhone) to convert it into an importable .mcworld so everyone can play in Bedrock. Conversion is pay-per-use with an automatic refund on failure, and it never overwrites your source file—your original Java world is preserved, hash and all, fully traceable.
  • Rebuild it by hand on Java. If you have to stay on Java Edition, your only option is to recreate it manually in Java using the original as a reference; there is no automatic Bedrock-to-Java tool to skip that step.

Check what transfers before you convert

Even in the supported Java to Bedrock direction, we don’t promise ‘100% lossless.’ Before you pay, we give you a compatibility score that spells out what transfers in full (terrain, the vast majority of blocks, containers, structures) and what may be replaced or moved into a separate report (Java-only entities, behavior/resource packs, some redstone behavior, player data). For details, see Java to Bedrock: what transfers and what doesn’t. When it’s done you get a line-by-line change report, so there are no surprises.