Safety & undo

What it leaves alone

• Your old version. Nothing is written into the old version’s settings folder or program folder, and its plugins.json is not changed — so it keeps working exactly as before. (The one exception is the optional Cleanup step, which deletes the old version only when you ask it to.)
• Your external plugin folders. They are cloned to a new, year-named folder; the original is only read. See Plugins.
• Anything until you click Migrate. Choosing versions, answering questions and reading the Preview write nothing.

Checks before it starts

• Cinema 4D open — the Preview shows a red card if any copy is running. Quit it: Cinema 4D saves its preferences when it quits, and would write over the migrated ones.
• Folders it can’t reach — if any folder the plan needs can’t be read or written, the Preview shows Cannot start this migration, says why and how to fix it, and Migrate stays disabled. Nothing is half-done: the migration either starts with access to everything, or not at all. You can also go back and untick the items that need those folders.

The snapshot

With Snapshot the new version first ticked on the Preview (it is by default), the migrator copies the new version before it changes anything:

• its whole settings folder (a freshly launched version is small — tens of megabytes);
• everything else the plan will write to outside it — plugins and scripts in the program folder, the command-line and Team Render folders, cloned external plugin folders. Where one of those doesn’t exist yet, the snapshot notes that, and restoring removes it.

If the snapshot can’t be taken, the migration doesn’t run.

Snapshots are kept in:

• Windows — %APPDATA%\Chroma C4D Migrator\snapshots\
• macOS — ~/Library/Application Support/Chroma C4D Migrator/snapshots/

They aren’t deleted automatically. Once you are happy with a migration you can delete old ones from there to save space.

Backups of replaced files

When a merge replaces a file the new version already had (a preferences file, a script, a layout), the original is copied first to:

<new version’s settings folder>/_migrator_backup/<date and time>/

keeping its place in the folder structure. One backup folder per run, made only if something was actually replaced.

Files overwritten because you ticked Replace if it already exists are covered by the snapshot, not by _migrator_backup.

Three ways back

	Where	What it does
Restore snapshot	The Report, and the Welcome screen next time	Puts the new version back exactly as it was before the migration. Anything you have changed in that version since is lost.
Revert migration	The Report	Undoes this run: removes what it created, and puts back files a merge replaced, from _migrator_backup.
Factory reset	The Report, and the Welcome screen	Deletes the version’s settings so Cinema 4D starts fresh.

Quit Cinema 4D before any of them. All three refuse to run while it is open.

Restore snapshot

The most complete way back, and quicker than uninstalling and reinstalling Cinema 4D. The Welcome screen’s undo an earlier migration card lists your five most recent snapshots, each with a restore button.

Revert migration

Revert works through the run backwards:

• folders and files the run created are deleted;
• in folders it merged into, the files it added are removed and the ones it replaced are put back from the backup;
• a layout it merged over an existing one is put back the same way;
• command-line and Team Render links are removed.

Anything that already existed and was overwritten (with Replace if it already exists) can’t be reverted this way, because the migrator doesn’t hold the old copy — Revert leaves it and tells you how many actions it couldn’t undo. Use Restore snapshot for those.

Factory reset

Deletes the new version’s settings folder, its command-line, Team Render and other variant folders (_x, _c, _s, _p …), and anything a migration created for it elsewhere (such as a cloned external plugin folder). The dialog lists every path before you confirm. Cinema 4D rebuilds clean settings the next time it opens, and may ask you to choose your licence again. Your snapshots are kept, so you can still restore one afterwards.

Cleanup is permanent

The Cleanup step deletes the old version’s folders, including its application folder. No snapshot covers that. Only use it once you are sure the new version has everything you need.