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Verilator
Verilator compiles Verilog and SystemVerilog designs into C++ or SystemC models, with linting, coverage, and waveform-tracing options.
5 key claims verifiedOur editorial team checked this profile against product documentation, company information, vendor documentation. Supported by 5 documented sources.
Editorial overview
Aggregated Overview
The documented toolchain includes HDL linting, generated C++ and SystemC models, coverage, tracing, and API interfaces. It is free to use, but users must integrate builds and simulation workflows; no reliable public review rating or review sample was verified. Scores are editorial assessments, not user ratings or hands-on test results.
This profile combines documented product information and independent evidence where available. It is not a hands-on test unless TechZella explicitly identifies one.
Overview
Verilator is an open-source tool for working with Verilog and SystemVerilog hardware designs. It compiles designs into C++ or SystemC models, which users build and run with a host toolchain.
Unlike a conventional event-driven simulator, its flow centers on generated models. It also supports linting, optional waveform tracing and coverage, and JSON output for downstream tools. Teams should check language coverage and simulation semantics against their existing testbenches before adopting it.
Verilator Decision Snapshot
A quick way to understand who this product may suit, where its limits matter, and which facts are most relevant before you compare alternatives.
Best suited to
Hardware and software development teams that can build C++ or SystemC-based simulation flows and want HDL linting or compiled RTL models integrated with their tools.
Look elsewhere if
Teams needing a drop-in, event-driven simulator with full four-state behavior, SDF annotation, or mixed-signal simulation should evaluate those requirements carefully; Verilator documents limitations in these areas, and should evaluate alternatives such as Icarus Verilog or Siemens Questa One Simulation instead.
Platforms
Docker, FreeBSD, Linux, macOS, Windows
TechZella assessment
7.5/10
Verilator — What Sets It Apart?
These are the product-specific differences that may matter when deciding whether the software fits your workflow. They are based on documented evidence rather than a universal ranking.
- Generates compiled C++ or SystemC models rather than operating only as a conventional event-driven simulator.
- Combines lint-only checking with model generation, optional coverage, waveform tracing, and JSON output for downstream tools.
- Documents C++ model APIs and SystemVerilog DPI support for connecting designs to custom software.
Verilator Pros & Cons
Pros
- Free software with two licensing options.
- Generates C++ or SystemC models that can be integrated into user software.
- Combines linting, simulation-model generation, optional coverage, and waveform tracing.
- Supports Docker-based use and common source/build workflows.
Cons
- Some designs may require significant memory during model generation.
- C++ simulation commonly requires a user-written wrapper and evaluation loop.
- VPI support is limited and requires explicit signal exposure.
- The project documents limitations for X/Z handling, SDF annotation, and mixed-signal simulation.
Verilator Gotchas & Operational Limits
These are documented constraints or practical friction points that may matter before you adopt the product.
Very large designs may need substantial memory during Verilation.
Model generation can exceed the memory required to run the resulting simulation, so machine capacity and hierarchical workflows matter.
Evidence source ↗VPI support is a limited subset and requires explicitly marking signals for access.
Testbenches expecting unrestricted VPI access or immediate propagation after writes may need adaptation.
Evidence source ↗Verilator Pricing & Plans
Open-source software
$0
one-time
Free software under LGPL version 3 or the Perl Artistic License version 2.0. External commercial support is listed separately and has no public prices on the project page.
Check current pricing →Pricing may change. Verify current plans on the vendor's website.
Verilator Competitors & Alternatives
Compare similar products directly, then see which alternatives may make more sense when your requirements differ.
At a glance
Developer Tools| Decision factor | Verilator | Icarus Verilog | Siemens Questa One Simulation |
|---|---|---|---|
| Execution model | Compiles HDL into C++ or SystemC models that are then built and executed. | The Icarus compiler normally emits vvp-format output, which the separate vvp runtime executes. Source ↗ | Not documented |
| Testbench integration | Supports C++ model wrappers, SystemC output, and SystemVerilog DPI; VPI is limited. | Its documentation describes a separate simulation runtime and documents VPI usage. Source ↗ | Not documented |
| Product scope | An open-source Verilog and SystemVerilog compiler, linter, and model generator with documented limitations for some simulator workflows. | Not documented | Siemens presents a commercial simulation suite with functional and fault-simulation offerings, including integrated debugging. Source ↗ |
Only factors supported by the available research are shown. The comparison is descriptive, not a ranking.
Direct competitors
These products address broadly similar requirements. The descriptions focus on documented reasons a buyer might compare them with Verilator.
Icarus VerilogExecution model: The Icarus compiler normally emits vvp-format output, which the separate vvp runtime executes.
Siemens Questa One SimulationSiemens presents a commercial simulation suite with functional and fault-simulation offerings, including integrated debugging.
Verilator Features
HDL compilation and linting
- Translate Verilog and SystemVerilog into C++ or SystemC models
- Generate a simulation executable
- Run lint-only checks
- Emit JSON output for downstream tools
Simulation and verification
- Optional waveform tracing
- Coverage support and coverage analysis
- Multithreaded generated models
- Limited VPI interface
Integration
- C++ model API and user-written wrapper support
- SystemVerilog DPI-C imports and exports
- Make and CMake build workflows
- Official Docker images
Verilator Specifications
| Input languages | Verilog and SystemVerilog; some Verilog AMS parsing support |
|---|---|
| Generated models | C++ or SystemC |
| Host operating systems | Ubuntu/Linux, macOS, FreeBSD, Windows, WSL2, Cygwin, and MinGW are documented with varying levels of testing |
| Containers | Official Docker images for released versions |
| API | C++ model API; SystemVerilog DPI-C; limited VPI subset |
| License | LGPL version 3 or Perl Artistic License version 2.0 |
| Latest documented release | 5.054, dated 2026-11-01 |
Deployment & System Footprint
Verified installation, hosting, administration, or environment details that can affect implementation.
| Installation or hosting | Install from a Linux distribution package, build from source, or use official Docker images. Verilator runs locally and generates models that are built with a C++ compiler; it is not a hosted SaaS product. Source ↗ |
|---|
Our evidence-based assessment
TechZella Score
A proprietary editorial score based on product capabilities, usability, value, performance, support and user sentiment evidence.
7.5/10Low confidence
The documented toolchain includes HDL linting, generated C++ and SystemC models, coverage, tracing, and API interfaces. It is free to use, but users must integrate builds and simulation workflows; no reliable public review rating or review sample was verified. Scores are editorial assessments, not user ratings or hands-on test results.
Methodology v1.0. The assessment weighs feature coverage (25%), ease of use (15%), value for money (20%), performance (15%), support (10%) and user sentiment (15%), using researched product evidence and verified review evidence where available. It is a TechZella editorial assessment, not a direct user-review average.
Editorial transparency
Our Review Methodology
Key claims are linked to the sources used to verify them. This evidence record is separate from third-party user ratings.
TechZella evaluates software using documented product capabilities, pricing information, usability and value considerations, independent user evidence where available, and competitive context. The assessment is an editorial review, not a hands-on test unless one is explicitly identified. Our editorial assessment is based on 5 documented sources.
What TechZella adds
- Generates compiled C++ or SystemC models rather than operating only as a conventional event-driven simulator.
- Combines lint-only checking with model generation, optional coverage, waveform tracing, and JSON output for downstream tools.
- Documents C++ model APIs and SystemVerilog DPI support for connecting designs to custom software.
Important limitations
- The project notes that X and Z handling is limited and that it may not replace a full-featured closed-source simulator for SDF annotation or mixed-signal work.
- C++ mode requires a user-written wrapper and simulation loop unless using the generated binary option.
- Large designs can require substantial memory during model generation; the FAQ reports that very large designs have exceeded 64 GB resident memory.
Evidence-backed claimsVerilator converts Verilog and SystemVerilog designs into C++ or SystemC models. Verilator supports lint-only operation and JSON output as well as model generation. The project is free software under LGPL 3 or the Perl Artistic License 2.0. The project began in 1994 at Digital Equipment Corporation. Version 5.054 was released on November 1, 2026, and added a separate branch-coverage option.
The user guide describes the translation workflow and generated executable or model output.
View source ↗Verified 2026-11-10The user guide lists `--lint-only`, `--json-only`, C++ and SystemC generation, and binary generation modes.
View source ↗Verified 2026-11-10The project repository identifies the two available licenses.
View source ↗Verified 2026-11-10The project history says Verilator was conceived in 1994 by Paul Wasson at DEC.
View source ↗Verified 2026-11-10The revision history dates version 5.054 and describes the new `--coverage-branch` option.
View source ↗Verified 2026-11-10Verilator FAQs
Answers begin with the clearest available response, followed by the context that helps you act on it.
Is Verilator free?
Yes. The project distributes Verilator under either LGPL version 3 or the Perl Artistic License version 2.0.
Does Verilator run on Windows?
Yes. The project recommends Ubuntu under WSL2; Cygwin and Microsoft Visual C++ output are also described, but are not regularly tested.
Does Verilator support C++ and SystemC?
Yes. It can generate C++ or SystemC models, and its C++ mode exposes an API for connecting to generated models.
Does Verilator support VPI?
Yes, but only a limited subset. The documentation says signal access must be selected explicitly, and callers need to evaluate the model after VPI writes.
Does Verilator have a free trial?
No. A trial is not applicable to the free open-source software. Separate commercial support is available from listed providers, whose terms and prices are not specified on the project page.
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