# Checkers
A checker validates its input files and produces no output. A passing check is
recorded as a cache marker, so unchanged inputs are not checked again. See
[Processor Types](../../processor-types.md#checker) for how checkers work.
The pages in this section document the built-in checkers. These checkers have
no dedicated page yet: duplicate_files, encoding, ijq, ijsonlint, itaplo,
iyamllint, license_header, marp_images, prettier, svglint, svgo.
Run `rsconstruct processor list` for the full list with each processor's type.