Online Assembly Compiler

NASM (Netwide Assembler) is a popular x86/x86_64 assembler for Linux and Windows, with syntax that balances readability and direct access to CPU instructions. "Assembly" on this page means NASM-flavoured x86_64 — the same dialect taught in OS-development courses and used in CTF reverse-engineering challenges.

Assembling and linking a NASM snippet by hand requires nasm, ld, and a Linux sandbox — a heavyweight setup for a five-instruction experiment. A browser sandbox backed by our execution platform lets you assemble a snippet, dump machine code to stdout, and observe the program's exit code without touching a toolchain.

Operating-system development (bootloaders, kernel entry points, context switches), reverse-engineering Capture-The-Flag challenges, performance-critical inner loops, embedded firmware for resource-constrained microcontrollers, and security research (ROP chains, shellcode, format-string exploits). The sandbox runs NASM, links to ELF64, and invokes the program via direct Linux syscalls.

The default snippet exits with code 0 using the sys_exit syscall. Try replacing the mov rax, 60 with mov rax, 1 to switch to sys_write, or modify the mov rdi, rdi line to change the exit code. The highlighter recognises section .text, section .data, labels, the mov/syscall/int opcodes, and x86_64 register names.

An online Assembly compiler in this context is a free NASM assembler running against a real Linux sandbox — your code gets assembled to ELF64, linked, and executed via direct syscalls, so register state and exit codes are exactly what a local nasm + ld pipeline would produce. There's no toolchain to install and no linker flags to get right; paste instructions, hit Run, and watch the exit code and any sys_write output land in the panel.

Assembly coursework almost always sits next to C and C++, so the Online C Compiler and Online C++ Compiler are useful for seeing what a compiler generates versus what you write by hand.

Running assembly code in the browser means skipping the usual setup of nasm, a linker, and a Linux environment just to test five instructions. Paste a routine, hit Ctrl+Enter, and trace the register state and arithmetic the way an architecture lab expects — mov, syscall, and the rest execute against a genuine x86_64 sandbox, not a simulator with gaps.

If the same coursework touches a systems language with its own calling conventions, the Online Zig Compiler is a useful comparison point. The rest of the catalogue is on the Online Compiler hub.

Assemblers, calling conventions, and even register-naming quirks differ enough between Windows and Linux that "install NASM locally" is really three different setups depending on the OS. This free NASM assembler standardises on one Linux/ELF64 environment so a lab exercise behaves identically regardless of what the student's laptop is running — useful for coursework and CTF practice, not a replacement for a real OS-dev toolchain once you're past the five-instruction stage.

Zig is a common next step for anyone moving from raw assembly toward a systems language — the Online Zig Compiler is one click away, and the free online compiler hub covers everything else.