Duplo vs Fallow

Duplo is a free tool for locating duplicated source-code blocks in large codebases. It has built-in language support for C/C++, Java, C#, VB, GCC assembly, Ada, Erlang, TypeScript and Swift, and can also scan arbitrary text files, including for duplicates within one file. For supported languages, it can filter comments, preprocessor directives and other syntax before checking for repeated code. Files can be provided through standard input or a separate file list. Duplo produces text reports as well as JSON and XML output. The project describes XML reports as usable in continuous integration tools such as GitHub Actions and TeamCity, and links to a GitHub Actions extension that can fail a build when duplicates are found. That extension has settings for minimum duplicate lines, minimum line length and maximum files reported. Prebuilt binaries are available for Alpine Linux, macOS and Windows; it can also be built from source. Duplo is free under GNU GPL version 2 or later, and is provided without warranty.

Fallow has no write-up on Specifiction yet; its figures are above.