DRAT-trim: efficient checking and trimming using expressive clausal proofs. The DRAT-trim tool is a satisfiability proof checker based on the new DRAT proof format. Unlike its predecessor, DRUP-trim, all presently known SAT solving and preprocessing techniques can be validated using DRAT-trim. Checking time of a proof is comparable to the running time of the proof-producing solver. Memory usage is also similar to solving memory consumption, which overcomes a major hurdle of resolution-based proof checkers. The DRAT-trim tool can emit trimmed formulas, optimized proofs, and new TraceCheck$^{ + }$ dependency graphs. We describe the output that is produced, what optimizations have been made to check RAT clauses, and potential applications of the tool.