The ppxlib project provides the basis for the ppx system, which is currently the officially supported method for meta-programming in Ocaml. It offers a principled way to generate code at compile time in OCaml projects. It features: - an OCaml AST / parser/ pretty-printer snapshot, to create a full frontend independent of the version of OCaml; - a library for ppx rewriters in general, and type-driven code generators in particular; - a full-featured driver for OCaml AST transformers; - a quotation mechanism for writing values representing OCaml AST in the OCaml syntax; - a generator of open recursion classes from type definitions.