Methods, systems, and apparatus, including computer programs encoded on computer storage media, for matching and attributing code violations. One of the methods includes receiving a snapshot S of a code base of source code and a different snapshot T of the code base. Data representing first violations in the snapshot S and second violations in the snapshot T is received. Pairs of matching violations are determined using performing two or more matching processes, including performing a first matching process, the first matching process determining first pairs of matching violations according to a first matching algorithm and performing a second matching process, the second matching process determining second pairs of matching violations according to a second matching algorithm from violations not matched by the first matching process. The first pairs of matching violations and the second pairs of matching violations are included in the determined pairs of matching violations.