The sampling standard that lets you inspect a sample, not 100%, and still decide reliably.
AQL (Acceptable Quality Limit) is a statistical sampling standard (ISO 2859-1 / ANSI Z1.4) that tells an inspector how many units to pull from a batch and how many defects to allow before the batch is rejected. It lets you inspect a representative sample instead of 100% of an order and still make a reliable accept-or-reject decision.
From your lot size (total units) the standard gives a sample size to inspect, and for your chosen AQL level, an accept and reject number. If the sample has that many defects or fewer, the lot is accepted; more, and it is rejected. It is a way to judge a whole batch fairly from a small, statistically valid sample.
A widely used consumer-goods setting is 0 critical / 2.5 major / 4.0 minor, meaning progressively more minor defects are tolerated than major ones and no critical defects at all. Tighten the numbers for higher-value or safety-related products, loosen them for low-cost items — the AQL should match what a defect actually costs you.
AQL is a sampling decision rule, not a guarantee that every unit is perfect. It controls the risk of accepting a bad batch, and it is only as good as the spec and golden sample the inspector judges against. Set the classes and levels before the inspection, and pair AQL with a clear specification — the number means nothing without a definition of "defect".