Preflight
Know what an import will change, before it changes it
Preflight imports data into an OpenCart store in bulk in two steps that are deliberately kept apart: it writes a plan of every change it would make, and only writes to your catalogue once you have read it. That is the whole product — know first, write second, undo if you were wrong.
A plan before a write
Preflight reads your file and writes a plan: every record it would create, every field it would alter with the value that field holds right now, and every row it had to reject. Nothing has been written at that point.
An applied import can be rolled back
Applying records the previous value of every field it touches, so the whole job can be undone afterwards — and the rollback is previewed before you confirm it.
A row it cannot read is rejected, not guessed at
A price that reads “on request” is reported in the plan rather than quietly turned into 0.00. Preflight tells you your file is wrong; it does not decide what you meant.
Your store’s columns, not a fixed list
Fields are mapped against the columns your store actually has, so a column another extension added is mappable with no configuration and no code change.
Where rollback stops is written out rather than glossed over: limits and guarantees states exactly what it restores, what it declines to touch, and why. It is the page worth reading before you point Preflight at a catalogue you care about.