Switching skin editions reloads the page, and that is the correct design
Java's editor is built around 64 and Bedrock's around 128. The constant is baked in, so the two cannot hand each other a canvas — which is why each edition is a real URL rather than a toggle.
The skin editor here is two programs, not one program with a setting. Picking Java or Bedrock loads a different build and reloads the page, and the reason is worth understanding because it explains a class of "why won't my skin import" question.
Two builds, two texture sizes
- Java —
TEXTURE_SIZE64. Accepts 64 × 64, or legacy 64 × 32. Rejects everything else. - Bedrock —
TEXTURE_SIZE128. Accepts 128 × 128 and nothing else.
That constant is not a variable the running editor consults; it is baked into each build. The two therefore cannot hand a canvas to each other — there is no shared representation for them to pass. Swapping a value at runtime would leave one half of the program working in the wrong units.
So the edition switch reloads. #bedrock on the URL opens the Bedrock build, which makes each edition a real address you can link to, bookmark and share, rather than a hidden toggle state that a fresh visitor cannot reach.
Neither can display the other's skin
This is the part that surfaces as a support question. A Java skin loaded into the Bedrock editor does not render at quarter size; it is rejected. A Bedrock skin in the Java editor is rejected too.
The instinct is that 128 × 128 is "the same layout, bigger", so it should scale. It is not — it is a different UV layout at a different size, with parts in different places. There is no resampling that converts one into the other, and a tool offering to do it would be guessing.
If you have the wrong file for the editor you are in, the fix is the edition switch, not an image editor.
What that means for your workflow
Decide the target platform before you start drawing, not after. A finished Java skin is not one export step away from being a Bedrock skin.
If you need both, they are two pieces of work that happen to look similar — and the shared thing between them is the design, not the file.