This is a list of real-time operating systems (RTOSs). This is an operating system in which the time taken to process an input stimulus is less than the time lapsed until the next input stimulus of the same type.

Name License Source model Target uses Status Platforms Apache Mynewt open source embedded activeARM Cortex-M, MIPS32, Microchip PIC32, RISC-V BeRTOS open source embedded archived ARM, Cortex-M3, ARM ARM7TDMI, Atmel AVR, PowerPC (emu), x86 (emu), x86-64 (emu) ChibiOS/RT open source embedded, small footprintactive x86, ARM7, ARM9, Cortex-M0-M3-M4, PowerPC e200z, STM8, STM32, AVR, MSP430, ColdFire, H8S ChorusOS defunct SPARC, x86, PowerPC Contiki open source embedded, WSN active MSP430, AVR, ARM Data General RDOS general purpose defunct Data General Nova, Data General Eclipse Deos closed safety critical active x86, PowerPC, ARM, MIPS DioneOS available for licensee embedded MSP430, MSP430x DNIX closed general purpose defunct 68000 Emboxopen sourceembeddedactivex86, ARM, Microblaze, SPARC, PPC, MIPS GEC DOS closed process control defunct GEC 4000 series DSOS closed defunct TI-980A minicomputer DSP/BIOS closed, available with license general purpose maintenance only Mostly Texas Instruments C2800, C5500, C6000 and OMAP DSP cores. Replaced by TI-RTOS, but available for download. eCos open source embedded inactive ARM-XScale-Cortex-M, CalmRISC, 680x0-ColdFire, fr30, FR-V, H8, IA-32, MIPS, MN10300, OpenRISC, PowerPC, SPARC, SuperH, V8xx eCosPro open source with non-free portions active ARM7-9, Cortex-A5-A9-M3-M4-M7, 680x0-ColdFire, H8-H8S, IA-32, MIPS32, MIPS64, microMIPS, NIOS II, OpenRISC, PowerPC, SPARC, SH4/4A, TILE-Gx, XScale embOS closed, available to customers, free object code for non-commercial use embedded, industrial, IoT, safety critical active ARM7/9/11, ARM Cortex-A/R/M, AVR, AVR32, C16x, CR16C, ColdFire, H8, HCS12, M16C, M32C, MSP430, NIOS2, PIC18/24/32, R32C, R8C, RISC-V, RL78, RH850, RX100/200/600/700, RZ, SH2A, STM8, ST7, V850, 78K0, 8051 ERIKA Enterprise open source embedded ARM7, ARM Cortex-M, ARM Cortex-A (on Jailhouse hypervisor), Hitachi H8, Altera Nios2, Microchip dsPIC (including dsPIC30, dsPIC33, and PIC24), Microchip PIC32, ST Microelectronics ST10, Infineon C167, Infineon Tricore, Freescale PPC e200 (MPC 56xx) (including PPC e200 z0, z6, z7), Freescale S12XS, EnSilica eSi-RISC, AVR, Lattice Mico32, MSP430, Renesas RX200, x86-64 (on Jailhouse hypervisor) EROS open source experimentalresearch use dormant IA-32 FlexOS closed general purpose, industrial, POS defunct 186, 286, 386, V60, V70, 68000 FreeRTOS open source embeddedactive ARM, AVR, AVR32, ColdFire, ESP32, HCS12, IA-32, Cortex-M3-M4-M7, Infineon XMC4000, MicroBlaze, MSP430, PIC, PIC32, Renesas H8/S, RISC-V, RX100-200-600-700, 8052, STM32, TriCore, EFM32 Fuchsia embedded AArch64, x86-64 Keil RTX open source embedded Arm Cortex-M FunkOS open source embedded AVR, MSP430, Cortex-M3 HeartOS closed safety critical x86, PowerPC, ARM Huawei LiteOS open source embedded defunct ARM (M0/3/4/7, A7/17/53, ARM9/11), x86, RISC-V HarmonyOS closed embedded active AArch64, x86-64, RISC-V, LingxiISAHorizon closed embedded, gaming ARM11, AArch64 IBM 4680 OS closed general purpose, industrial, POS defunct 286 IBM 4690 OS active 286, 386 INTEGRITY embedded ARM, XScale, Blackfin, ColdFire, MIPS, PowerPC, x86 INtime x86 ITRON varies embedded ARM, MIPS, x86, Renesas RX100-200-600-700-others Kaspersky OS open source safety critical, virtualization x86, x86_64, ARMV5, ARMV7, ARMV8, MIPS32 KolibriOS embeddable x86 LynxOS source available embedded Motorola 68010, x86/IA-32, ARM, Freescale PowerPC, PowerPC 970, LEON Mbed OS open source embedded abandoned Arm Cortex-M MenuetOS open source active IA-32 MERT (Bell Labs) closed OS for long-distance telephone switching systems inactive PDP-11 MicroC/OS-III open source embedded active ARM7-9-11/Cortex-M1-3-4-A8/9, AVR, HC11/12/S12, ColdFire, Blackfin, MicroBlaze, NIOS, 8051, x86, Win32, H8S, M16C, M32C, MIPS, 68000, PIC24/dsPIC33/PIC32, MSP430, PowerPC, SH, StarCore, Renesas RX100-200-600-700, RL; STM32, ... MontaVista Linux open source embedded active x86, ARM, PowerPC, MIPS, RISC-V MP/M closed (meanwhile: open source) general purpose, industrial defunct 8080, Z80, 8086 MQX complimentary source available embedded active Freescale Power, ColdFire, Kinetis Cortex ARM, List of Freescale products Multiuser DOS closed general-purpose, industrial defunct 386 Nano-RK open source embedded, WSN defunct AVR, MSP430 Neutrino some source provided microkernel, embedded, industrial active ARM, ARM64, MIPS, PPC, SH, x86, x86-64, XScale Nucleus RTOS source provided embedded ARM (Cortex-M3-M4-R4-R4F-A8-A9, ARM7-9-11), PowerPC, MIPS32-16e, microMIPS, ColdFire, SuperH NUT open source embedded, industrial ARM-M0, ARM-M0+, ARM Cortex-M3, ARM9, ARM Cortex-M7, Cortex-M3 Nut/OS embedded, industrial AVR, AVR32, ARM7, ARM9, Cortex-M3 NuttX open source embedded, small footprint Linux user mode, ARM7-9, Cortex-A5-A8-A9-M0-M3-M4-M7, 8052, Espressif ESP32, Lattice LM32, Renesas MC16C/26/SH-1, RISC-V, Zilog Z16F, Zilog eZ80 Acclaim!, Zilog Z8Encore!, Z80, MIPS PIC32MX, PIC32MZ OpenComRTOS source provided embedded Freescale PowerPC, Texas Instruments C66xxx DSP, ARM, XMOS, MicroBlaze, LEON, NXP CoolFlux DSP, Melexis MLX16, Win32, Linux OS2000 embedded active MIPS (Baget variant), KOMDIV-32, KOMDIV-64, Intel BSPs (x86) OS4000 closed process control maintenance only GEC 4000 series OSE available to customers general purpose active ARM, PowerPC, x86, TI OMAP, ... OS-9 available to customers embedded ARM-strongARM, MIPS, PowerPC, SuperH, x86/Pentium, XSCALE, Motorola 6809, 680x0, SPARC OSEK specification engine control units Phoenix-RTOS open source embedded active ARMv7 Cortex-M, ARMv7 Cortex-A, IA-32, RISC-V PikeOS available to customers certifiable safety & security, embedded virtualisation PPC, x86, ARM, MIPS, SPARC-LEON, RISC-V Protothreads open source general purpose active Architecture independent pSOS discontinued 680x0 PX5 RTOS royalty-free licensing embedded active Embedded MCU and MPU architectures. ARM's Cortex-M, Cortex-R, Cortex-A, RISC-V. AMP and SMP configurations. QNX microkernel, embedded, industrial active QP dual MCU, DSC, DSP SoC ARM7/9, ARM Cortex-M3-M0, MSP430, TMS320C28x, AVR, AVRXmega, ColdFire, 68HC08, M16C/R8C, H8, 8051, 80251, PIC18, PIC24/dsPIC33, Nios II, PSoC1 REAL/32 closed general-purpose, industrial 386 Real-time Linux (PREEMPT RT) open source general purpose x86, x86_64, RISC-V, ARM64 and LoongArch (ARM and POWER in the -rt branch)PREEMPT_RT patch versions REX OS closed, available with license embedded inactive ARM RIOT open source active ARM7, ARM Cortex M, MSP430, AVR, RISC-V, Xtensa RMX closed defunct Intel 8080, 8086, 80386, higher RODOS source provided active ARMv7 (M3, A8, A9), AVR32, PowerPC 405, SPARC64 Platforms: SmartFusion2, RaspberryPi, STM32 On an OS: Linux, Windows, macOS, FreeRTOS, RTEMS RSX-11 historic PDP-11 RT-11 general purpose defunct PDP-11 RTAI open source general purpose active x86 (with and without FPU and TSC), x86-64, PowerPC, ARM (StrongARM; ARM7: clps711x-family, Cirrus Logic EP7xxx, CS89712, PXA25x), m68k (supporting both MMU and NOMMU cpus) RTEMS embedded AArch64, ARM, Blackfin, ColdFire, TI C3x/C4x, H8/300, x86, x86_64, 68k, Microblaze, Milkymist SoC, MIPS, Nios II, PowerPC, SuperH, SPARC, ERC32, LEON, Mongoose-V RTLinux general purpose inactive same as Linux RT-Thread open source embedded active ARM, ARM Cortex-M0-M3-R4-M4-M7, IA-32, AVR32, Blackfin, nios, PPC, M16C, MIPS (loongson-1b-1c, PIC32，xburst), MicroBlaze, V850, unicore32, RTXC Quadros source available embedded ARM - Atmel/Freescale/NXP/ST/TI, Blackfin, 680x0-ColdFire, PowerPC, StarCore, TI-Luminary Stellaris, TI OMAP, XScale RTX, RTX64 closed MS Windows extension x86, x86-64 RX116 embedded, industrial defunct NEC V20, NEC V30, NEC V40, NEC V50 RX616 safety critical, embedded, industrial NEC V60, NEC V70 RX-UX832 embedded, industrial, general-purpose NEC V60, NEC V70 SCIOPTA available to customers safety-critical, embedded active ARM (Cortex-M, Cortex-R, Cortex-A), ARM64, Infineon AURIX, Renesas RX, Analog Devices Blackfin, Power architecture SafeRTOS source code & Design Assurance Pack available embedded, safety critical active Same as FreeRTOS SuperTinyKernel RTOS open source embedded, IoT, safety critical active ARM Cortex-M (ARMv6-M through ARMv8.1-M: M0, M3, M4, M7, M33, M55), RISC-V (RV32I, RV32E), x86 (Simulator mode) SHaRK open source inactive Simulink Real-Time closed real-time testing-embedded active x86 SINTRAN III Norsk Data computers Symbian OS open source embedded defunct ARM T-Kernel source available embedded RTOS active ARM, MIPS, SH, more THEOS ThreadX open source embedded, IoT, safety critical active ARC, ARM/Thumb, AVR32, BlackFin, 680x0-ColdFire, H8-300H, Luminary Micro Stellaris, M-CORE, MicroBlaze, PIC24-dsPIC, PIC32, MIPS, V8xx, Nios II, PowerPC, Renesas RX100, RX200, RX600, RX700, Synergy, SH, SHARC, StarCore, STM32, StrongARM, TMS320C54x, TMS320C6x, x86/x386, XScale, Xtensa/Diamond, ZSP TI-RTOS Kernel (SYS/BIOS) open source embedded Mostly Texas Instruments: MSP430-432, C2000-5000-6000, TI's ARM families (Cortex M3-4F-R4-A8-A15), SimpleLink Wireless CC2xxx-CC3xxx TizenRT open source embedded active Transaction Processing Facility mixed general purpose active IBM Z series TRON project mixed mixed active any: is a specification, not an implementation UNIX-RTR defunct PDP-11 UNOS historic 680x0 μITRON open source embedded active ARM, MIPS, x86, Renesas RX100-200-600-700-others μ-velOSity microkernel active velOSity Power ISA, ARM/XScale, MIPS, x86/Pentium, ColdFire, Blackfin, OMAP, DaVinci VAXELN closed source historic VAX VRTX superseded by Nucleus RTOS ARM, MIPS, PowerPC, RISC VxWorks embedded active ARM, IA-32, Intel 64, MIPS, PowerPC, SH-4, StrongARM, xScale Windows CE Microsoft Shared Source x86, MIPS, ARM, SuperH Windows 10 IoT Intel Atom, Celeron, Pentium; Qualcomm Snapdragon, Broadcom, NXP i.MX Xenomai open source general x86, x86-64, PowerPC, ARM, Analog Devices Blackfin BF52x, BF53x, BF54x and BF56x XINU embedded active x86, MIPS, ARM, AVR XMK open source embedded inactive Zephyr open source embedded active ARM (Cortex-M0, -M3, -M4, -M23, -M33, -R4, -R5, -A53), x86, ARC, RISC-V, Nios II, Xtensa, SPARC

References

External links 2026 RTOS Performance Report (FreeRTOS, NuttX, PX5, RT-Thread, RTX5, ThreadX, uC/OS-III, Zephyr) - Beningo Embedded Group 2024 RTOS Performance Report (FreeRTOS, ThreadX, PX5, Zephyr) - Beningo Embedded Group 2013 RTOS Comparison (Nucleus, ThreadX, uC/OS, Unison) - Embedded Magazine 2020 Timing Comparison of the RTOSs for STM32 Microcontrollers (FreeRTOS, RT-Thread, RTX, uC/OS-II, uC/OS-III) - Symmetry