heapsize provides functions to determine the size of Haskell data structures in memory at run time, including circular data structures. All sizes are reported in bytes.
Determining the size of simple data structures is relatively quick, but large and complex data structures can be slow. For large and complex structures the user may want to find a way to and estimate the size of the full data structure from that.
heapsize is originally based on ghc-datasize, but adds support for ghc 8.10.1 and beyond, as well as improving performance.