This is an incomplete comparison of assemblers. Some assemblers are components of a compiler system for a high-level programming language and may have limited or no usable functionality outside of the compiler system. Some assemblers are hosted on the target processor and operating system, while other assemblers (cross-assemblers) may run under an unrelated operating system or processor. For example, assemblers for embedded systems are not usually hosted on the target system since it would not have the storage and terminal I/O to permit entry of a program from a keyboard. An assembler may have a single target processor or may have options to support multiple processor types.

• GNU Assembler (GAS): GPL: many target instruction sets, including ARM architecture, Atmel AVR, x86, x86-64, Freescale 68HC11, Freescale v4e, Motorola 680x0, MIPS, PowerPC, IBM System z, TI MSP430, Zilog Z80.
• SDAS (fork of ASxxxx Cross Assemblers and part of the Small Device C Compiler project): GPL: several target instruction sets including Intel 8051, Zilog Z80, Freescale 68HC08, PIC microcontroller.
• The Amsterdam Compiler Kit (ACK) targets many architectures of the 1980s, including 6502, 6800, 680x0, ARM, x86, Zilog Z80 and Z8000.
• LLVM targets many platforms, however its main focus is not machine-dependent code generation; instead a more high-level typed assembly-like intermediate representation is used. Nevertheless for the most common targets the LLVM MC (machine code) project provides an assembler both as an integrated component of the compilers and as an external tool.
• Some other self-hosted native-targeted language implementations (like Go, Free Pascal, SBCL) have their own assemblers with multiple targets. They may be used for inline assembly inside the language, or even included as a library, but aren't always suitable for being used outside of their framework - no command-line tool exists, or only the intermediate representation can be used as their input, or the set of supported targets is very limited.