What are “separate levels”?

In your project settings, you are given 2 options:

1. Saving everything to a single JSON file named myProject.ldtk.
2. Saving project data to a JSON file named myProject.ldtk and saving each level to a separate *.ldtkl (note the extra “L” at the end) file, in a sub-folder named myProject.

.ldtkl files

These files contain exactly the exact same level data as if it was in the main file, except it’s stored separately. It contains:

• a header to identify the file type,
• level data,
• all layers content.