Manual Profile Backup vs. Separate User Data Directories for Safe Chrome Rollback After Schema Change

The goal is to roll back to a previous Chrome version after a schema‑changing update without losing history, bookmarks, or preferences. Chrome stores profile data in SQLite and LevelDB files that carry a schema version; a downgrade can leave the older binary unable to interpret the new schema, causing read errors or silent truncation. The documented mitigation is to back up the entire user profile before updating and restore it if a rollback is required.

An alternative approach is to keep separate user‑data directories for each Chrome version, launching the browser with --user-data-dir to isolate profiles. This avoids overwriting the active profile but raises questions about storage overhead and profile synchronization. What are the practical trade‑offs between a full profile backup/restore strategy and maintaining parallel user‑data directories? Does isolating profiles eliminate the risk of schema‑version mismatch, or must additional checks still be performed? How much extra disk space is typically needed for the parallel‑profile method compared with periodic full backups?