exact match

An all-or-nothing metric in which the model's output either matches ground truth or the reference text exactly or it doesn't. For example, if ground truth is orange, the only model output that satisfies exact match is orange. Exact match can also evaluate models whose output is a sequence (a ranked list of items). In general, exact match requires the generated ranked list to exactly match ground truth; that is, each item in both lists must be in the same order. That said, if ground truth consists of multiple correct sequences, then exact match only requires model's output matches one of the correct sequences.

Practitioners refer to exact match when building, training, or evaluating machine learning systems. It appears in research papers, product documentation, and technical discussions about AI capabilities and limitations.