Olive oil is the only major cooking fat whose quality is invisible from the outside — and labels are written to exploit that. Most of what's printed on the front is marketing. The real information is small, and sometimes deliberately missing. Here is what to actually look for.
This is the single most useful thing on the bottle, and the thing most often left off. Olive oil is a fruit juice; it begins to fade the moment it's pressed. A 'best by' date (usually 18–24 months after bottling) tells you almost nothing — it can be set years after a late harvest. A harvest date (or 'crush date') tells you when the olives were actually picked. If a producer is proud of their oil, they print it. No harvest date is itself a warning sign.
By law, extra virgin olive oil (EVOO) must be mechanically extracted with no chemical refining, have free acidity below 0.8%, and pass a sensory panel with zero defects. Anything labelled simply 'olive oil', 'pure', 'light' or 'classic' has been refined — stripped of flavour and most of its health compounds. 'Light' refers to flavour and colour, never calories.
'Bottled in Italy' or 'packed in the EU' tells you where the factory is, not where the olives grew — oil is shipped in bulk and blended. Look for a single country or, better, a single region or estate. The EU marks PDO (Protected Designation of Origin) and PGI (Protected Geographical Indication) guarantee a specific place and method.
Light is one of olive oil's worst enemies. Quality oil is sold in dark glass, tinted bottles or tins — never clear plastic or clear glass on a bright shelf. The packaging itself is a quality signal: a producer who protects the oil from light usually protects it everywhere else too.