CSV/Excel Merger

Combine tabular files into one clean output without silently losing, duplicating, or corrupting rows.

Workflow

Copy this checklist and track progress:

- [ ] 1. Profile inputs
- [ ] 2. Choose append vs join
- [ ] 3. Map columns and normalize keys
- [ ] 4. Merge and resolve conflicts
- [ ] 5. Verify row math
- [ ] 6. Write output and report

1. Profile inputs. Run the bundled profiler first; it reports encoding, delimiter, rows, headers, candidate keys, and header overlap without changing anything: