Viper
Viper: A research-oriented toolkit for permission-based verification of mutable-state programs. Ranked #23 of 35 in Formal Verification Tools by our editors (7.2/10); pricing: Open source; best for permission-based heap verification.
At a glance
- Editor score7.2 / 10
- PricingOpen source
- Best forPermission-based heap verification
- Paid fromFree
- Verification methodHybrid
- Facts checked20 Sep 2026
Where it wins
- Permission and ownership reasoning for mutable state
- Z3-backed symbolic execution and verification-condition generation
- VS Code, CLI, and browser-based learning tools
Where it doesn't
- Self-hosted deployment requires managing the toolchain
- Direct use centers on the Viper language
- Language support depends on front-end tools for Go, Python, and Rust
Our verdict on Viper
Viper is open-source verification infrastructure from ETH Zurich for researchers and developers building verifiers for sequential and concurrent programs. It combines an intermediate verification language with imperative constructs, specifications, and automatic verification backends. The core focus is mutable state: permissions, ownership, implicit dynamic frames, and separation-logic-style reasoning. Teams can encode verification problems directly in Viper or use front-end tools for Go, Python, and Rust.
Its main technical strength is the combination of permission-based reasoning with multiple verification paths. Viper provides a symbolic-execution backend and a verification-condition-generation backend, while Z3 handles proof obligations. User-defined predicates and pure functions support more structured specifications. This makes Viper a strong fit for heap reasoning and contract-based verification where ownership and state access need to be expressed explicitly. The intermediate language also gives researchers a target for implementing additional front ends and verifiers.
Viper fits teams that want an open-source, self-hosted foundation rather than a hosted commercial service. The ecosystem includes Visual Studio Code, Boogie, Z3, Gobra, Nagini, and Prusti, with VS Code IDE support, command-line tools, and a browser-based interactive tutorial with runnable examples. That range supports both direct experimentation and language-specific workflows, but users working outside the listed front-end paths will need to work in the Viper language itself. Choose Viper for research, verifier construction, and permission-based heap verification; choose another tool if you need a managed SaaS experience or a workflow centered on a different verification formalism.
Questions about Viper
What does Viper run on? Web, Windows, macOS and Linux. It runs self-hosted.
What does Viper integrate with? 6 integrations, including Visual Studio Code, Boogie, Z3, Gobra and Nagini.
Who is Viper built for? Solo users and small businesses (our editorial estimate).
Your product? Our editors can test Viper in depth and publish a review, labelled as paid · from $149/mo →
Viper pricing
Viper fact sheet
| Free plan | Not verified |
|---|---|
| Paid from | Free |
| Verification method | Hybrid |
| Supported formalisms | Contracts |
| Counterexamples | Not verified |
| Proof artifacts | Not verified |
| Input languages | Viper language; Go, Python, and Rust via front-end tools |
| Deployment | Self-hosted |
| Deployment | Self-hosted |
| Platforms | Web, Windows, macOS, Linux |
| Support | Email, Community, Docs |
| Built for | Solo, Small business (editorial estimate) |
| Integrations | 6 integrations: Visual Studio Code, Boogie, Z3, Gobra, Nagini, Prusti |
| Pricing | Open source |
| Website | pm.inf.ethz.ch |
| Facts checked | 20 Sep 2026 |
Viper integrations
Viper lists 6 integrations on its own site.
- Visual Studio Code
- Boogie
- Z3
- Gobra
- Nagini
- Prusti
Alternatives to Viper
- IsabelleA free, open-source proof assistant for broad mathematical and systems verification.9.4
- RocqA free, kernel-checked theorem prover with dependent types, automation, and certified extraction.9.3
- PVSA broad, self-hosted environment for hybrid formal verification workflows.9.2
Used Viper? Be the first to review it
The editor score above is our own research. What this page doesn't have yet is a reader's view — what you used Viper for, what worked and what didn't. No stars are seeded and no review is paid for; an editor reads every one before it appears.
Write a reviewTwo minutes · verified accounts only · read by an editor before it appears
Featured on iTechGuides
Viper is listed in our Formal Verification Tools directory. Add the badge to your site — it links back to this page.
<a href="https://www.itechguides.com/products/viper-formal-verification-tool/"><img src="https://www.itechguides.com/best/badge/viper-formal-verification-tool.svg" alt="Featured on iTechGuides" width="230" height="46"></a>
Reviewed by iTechGuides Editors · Editorial team · Updated Nov 2026
Advertiser disclosure: iTechGuides is reader-supported. Vendors can pay for top positions in our rankings and for a place on other products' pages, and we may earn a commission when you click some links. Bought places stand at the number bought; this page and our disclosure say so. Paying vendors may get a fuller, more detailed review from our editors, and that review can change their score. How we rank.
Last updated · How we research and update