MTASC is built with optimizing OCaml compilers, and thus provides a speed improvement over the Macromedia Compiler (MMC). MTASC corrects several safety problems that occur when using MMC.} The MTASC compiler is stricter than MMC and can detect more errors than MMC; because of this strictness, there are some differences between MMC and MTASC.[clarification needed]
MTASC is not compatible with ActionScript 2.0 in the local variables scoping, local function definitions, et al.
MTASC will not support ActionScript 3.0, which is supported by its successor, Haxe.