JWasm is a free MASM-compatible assembler with these features:

* native support for output formats Intel OMF, MS Coff (32/64-bit), Elf (32/64-bit), Binary, Windows PE (32/64-bit) and DOS MZ.
* Instructions up to AVX are supported.
* JWasm is written in C. The source is portable and has successfully been tested with Open Watcom, MS VC, GCC and more.
* C header files can be converted to include files for JWasm with h2incX.
* JWasm's source code is released under the Sybase Open Watcom Public License, which allows free commercial and non-commercial use.

JWasm started as a fork of Open Watcom's Wasm in March 2008. Today, the part of Wasm source lines still contained in JWasm is approximately 20%.