For AI agents: the complete documentation index is available at /mbzoo/docs/llms.txt, the full documentation bundle is available at /mbzoo/docs/llms-full.txt, and this page is available as Markdown at /mbzoo/docs/guide/what-is-mbz.md.
MBZoo

    What is an .mbz?

    An .mbz file is a Moodle course backup: a package containing the course's sections, activities, files, settings and (optionally) user data.

    Container formats

    FormatSinceNotes
    ZIPMoodle 2.0No ZIP64 support inside Moodle itself (4 GB practical cap)
    TAR.GZdefault since 2.9 (opt-in 2.6)POSIX ustar; no size cap in practice

    MBZoo detects the format from magic bytes and supports both.

    Inside the archive

    moodle_backup.xml          course/section/activity skeleton, and the
                           settings that decide what else is in here
files.xml                  file index (contenthash, component, filearea…)
course/course.xml          full course metadata (fullname lives here)
sections/section_N/        per-section name, summary, activity order
activities/<mod>_N/        per-activity XML — see below
files/<2 hex>/<sha1>       content-addressed file pool
questions.xml              the question bank, shared by every quiz
gradebook.xml              category tree, aggregation, grade letters
users.xml                  the people — only when the backup was taken
                           with user data (see Privacy)

    An activity directory holds more than its module payload, and the siblings are where several things hide:

    activities/assign_42/
  assign.xml               the module's own settings and content
  module.xml               visibility, completion rules, availability, tags
  grades.xml               this activity's grade item: out of, pass, weight
  grading.xml              rubric or marking guide, when one is defined
  inforef.xml              which files.xml records this activity uses
  calendar.xml roles.xml competencies.xml filters.xml

    The setting that decides everything

    The single most useful thing to know about a .mbz is whether it was taken with user data. Every module writes its full XML tree either way; what the users setting gates is each element's data source.

    Two modules that look equally rich in the schema can be worlds apart in a real file. A lesson writes all of its pages and answers unconditionally — the whole authored lesson is there. A forum writes nothing but the forum record; every discussion and post is user data. That is why an empty glossary in a content-only backup is not a bug, and why MBZoo says why it is empty rather than just that it is.

    Always in the backupOnly with user data
    lesson pages and answers, choice options, database fields, workshop instructions and examples, quiz slots and the question bank, grade items and rubrics, the gradebook structureforum discussions and posts, glossary entries, database records, wiki pages, chat messages, assignment submissions, quiz attempts, everyone's marks

    A backup may be restored onto a different site, so Moodle cannot store absolute URLs for course-internal links. It rewrites them as $@COURSEVIEWBYID*62@$ tokens at backup time and decodes them at restore time. MBZoo never restores anything, so it decodes them for display instead — in-app navigation when the target travelled in the same backup, otherwise a labelled link to the site the backup came from, never fetched (ADR-0019).

    The same grammar carries $@NULL@$, which is Moodle's serialized SQL NULL — a field value, not a link, and never content.

    Facts verified against Moodle source (moodle/moodle, REPO-005) and against real backups, including courses generated in a real Moodle for the purpose — see research/ in the repository.

    What MBZoo does with it

    MBZoo parses the minimum XML subset needed to rebuild the course navigation tree, then extracts content (pages, PDFs, websites, questions…) on demand, in your browser. Nothing is uploaded — see Privacy.