Short answer: trust the compatibility report, not a “100% identical under any version” promise

TopoBlocks’s conversion is one-way Java → Bedrock (Bedrock cannot be converted back to Java), and it outputs a standard, importable Bedrock .mcworld.

But “version compatibility” isn’t something a single “supports 1.20/1.21” claim can guarantee. We don’t promise it will be 100% identical under any version: the vast majority of terrain and blocks can migrate, while a few version-specific content items may be replaced with compatible equivalents or flagged individually in the report. So the basis for judging compatibility is always the pre-conversion compatibility score and the post-conversion item-by-item change report—trust those, rather than drawing conclusions from a version number alone. To first understand the underlying differences between the two editions, see What’s the difference between Java Edition and Bedrock.

How is new-version (1.20/1.21) exclusive content handled?

  • Most blocks and terrain migrate as usual. The vast majority of blocks—including stairs, leaves, waterlogged states, and more—along with terrain, elevation, containers, and structure layouts, usually migrate fine.
  • Content with no direct counterpart is replaced or flagged. If your world contains a block or content item that is exclusive to a particular version and has no direct Bedrock counterpart, conversion will replace it with a compatible equivalent or move it into the item-by-item report with an explanation—it won’t pretend to copy it seamlessly. For which blocks tend to fall into this category, see Why blocks/coordinates don’t line up after conversion.
  • The report spells it out clearly. When it’s done, you’ll get an item-by-item change report listing every piece of content that was replaced or flagged—just cross-reference it before importing.

For a systematic overview of which categories migrate and which usually end up in the report, see Java to Bedrock: what transfers and what doesn’t.

A few notes for before and after importing

Conversion is pay-per-use with automatic refunds on failure, and prices are shown in-app. The whole process never overwrites your source file—your original Java world is preserved, hash included and traceable, and conversion only generates a new Bedrock .mcworld.

If you still run into problems importing into Bedrock, don’t rush to blame the version: many “import failures” are actually file structure/hierarchy issues rather than genuine version incompatibility. In that case, you can use TopoBlocks’s free on-device diagnosis to investigate, and do a simple structure repair if needed. By default, diagnosis runs on-device, uploads nothing, and never touches your original file.