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687 Stars 177 Forks GNU Lesser General Public License v3.0 4.5K Commits 187 Opened issues


Verilator open-source SystemVerilog simulator and lint system

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Welcome to Verilator

.. list-table::

  • - Welcome to Verilator, the fastest Verilog/SystemVerilog simulator. * Accepts synthesizable Verilog or SystemVerilog * Performs lint code-quality checks * Compiles into multithreaded C++, or SystemC * Creates XML to front-end your own tools
    • |Logo|
  • - |verilator multithreaded performance|
    • Fast
      • Outperforms many commercial simulators
      • Single- and multi-threaded output models
  • - Widely Used * Wide industry and academic deployment * Out-of-the-box support from Arm, and RISC-V vendor IP
    • |verilator usage|
  • - |verilator community|
    • Community Driven & Openly Licensed
      • Guided by the
        CHIPS Alliance
        _ and
        Linux Foundation
      • Open, and free as in both speech and beer
      • More simulation for your verification budget
  • - Commercial Support Available * Commercial support contracts * Design support contracts * Enhancement contracts
    • |verilator support|

What Verilator Does

Verilator is invoked with parameters similar to GCC or Synopsys's VCS. It "Verilates" the specified Verilog or SystemVerilog code by reading it, performing lint checks, and optionally inserting assertion checks and coverage-analysis points. It outputs single- or multi-threaded .cpp and .h files, the "Verilated" code.

The user writes a little C++/SystemC wrapper file, which instantiates the "Verilated" model of the user's top level module. These C++/SystemC files are then compiled by a C++ compiler (gcc/clang/MSVC++). The resulting executable performs the design simulation. Verilator also supports linking its generated libraries, optionally encrypted, into other simulators.

Verilator may not be the best choice if you are expecting a full featured replacement for NC-Verilog, VCS or another commercial Verilog simulator, or if you are looking for a behavioral Verilog simulator e.g. for a quick class project (we recommend

Icarus Verilog
_ for this.) However, if you are looking for a path to migrate SystemVerilog to C++ or SystemC, or your team is comfortable writing just a touch of C++ code, Verilator is the tool for you.


Verilator does not simply convert Verilog HDL to C++ or SystemC. Rather, Verilator compiles your code into a much faster optimized and optionally thread-partitioned model, which is in turn wrapped inside a C++/SystemC module. The results are a compiled Verilog model that executes even on a single-thread over 10x faster than standalone SystemC, and on a single thread is about 100 times faster than interpreted Verilog simulators such as

Icarus Verilog
_. Another 2-10x speedup might be gained from multithreading (yielding 200-1000x total over interpreted simulators).

Verilator has typically similar or better performance versus the closed-source Verilog simulators (Carbon Design Systems Carbonator, Modelsim, Cadence Incisive/NC-Verilog, Synopsys VCS, VTOC, and Pragmatic CVer/CVC). But, Verilator is open-sourced, so you can spend on computes rather than licenses. Thus Verilator gives you the best cycles/dollar.

Installation & Documentation

For more information:

  • Verilator installation and package directory structure
  • Verilator manual (HTML) 
    , or `Verilator manual (PDF) <>`_
  • Subscribe to verilator announcements
  • Verilator forum 
  • Verilator issues 


Verilator is a community project, guided by the

CHIPS Alliance
_ under the
Linux Foundation

We appreciate and welcome your contributions in whatever form; please see

Contributing to Verilator
. Thanks to our
Contributors and Sponsors

Verilator also supports and encourages commercial support models and organizations; please see

Verilator Commercial Support

Related Projects

  • GTKwave 
    _ - Waveform viewer for Verilator traces.
  • Icarus Verilog
    _ - Icarus is a full featured interpreted Verilog simulator. If Verilator does not support your needs, perhaps Icarus may.

Open License

Verilator is Copyright 2003-2021 by Wilson Snyder. (Report bugs to

Verilator Issues 

Verilator is free software; you can redistribute it and/or modify it under the terms of either the GNU Lesser General Public License Version 3 or the Perl Artistic License Version 2.0. See the documentation for more details.

.. CHIPS Alliance: .. _Icarus Verilog: .. _Linux Foundation: .. |Logo| image:: .. |verilator multithreaded performance| image:: .. |verilator usage| image:: .. |verilator community| image:: .. |verilator support| image::

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