Best Formal Verification Tools in 2026
Updated
In short: PVS is ranked #1 of 33 as of 5 October 2026, ahead of Rocq and Z3. The best-ranked option with a free plan is Rocq.
Formal verification tools help reason about whether a system satisfies stated properties. Compare supported formalisms and input languages to see what kinds of models or specifications each entry can work with. Verification method, counterexamples, and proof artifacts help distinguish how checks are performed and what evidence they produce. Deployment, free-plan availability, and paid-from pricing add practical considerations. PVS, Rocq, and Z3 are among the tools to examine. Consider the properties your work needs to validate, the inputs you can provide, and the form of result or evidence useful to your development process.
33 formal verification tools ranked on what their makers publish — plans and prices, free tiers, platforms and the facts on their own pages.
33ranked
8free plans on this page
5 Oct 2026last checked
Input list Formal Verification Tools 25 channels on this page · 140 of 200 spec lines stated by the makers
Ch Tool Free planPaid fromVerification methodSupported formalismsCounterexamplesProof artifactsInput languagesDeployment Spec sheet Score
01 PVS Free planYesPaid fromnot statedVerification methodhybridSupported formalismstheorem-provingCounterexamplesYesProof artifactsYesInput languagesPVS specification language (typed higher-order logic)Deploymentself-hosted 7/8spec lines stated 7.5
02 Rocq Free planYesPaid fromnot statedVerification methoddeductiveSupported formalismstheorem-provingCounterexamplesnot statedProof artifactsYesInput languagesGallina and Rocq vernacularDeploymentself-hosted 6/8spec lines stated 7.5
03 Z3 Free planYesPaid fromnot statedVerification methodnot statedSupported formalismstheorem-provingCounterexamplesYesProof artifactsYesInput languagesSMT-LIB2, C, C++, .NET, Java, Python, Rust, OCaml, Julia, JavaScript, TypeScript, Smalltalk, GoDeploymentself-hosted 6/8spec lines stated 7.4
04 Alloy Analyzer Free planYesPaid fromnot statedVerification methodmodel-checkingSupported formalismsinvariantsCounterexamplesYesProof artifactsnot statedInput languagesAlloy languageDeploymentself-hosted 6/8spec lines stated 7.2
05 UPPAAL Free planYesPaid fromnot statedVerification methodmodel-checkingSupported formalismsinvariantsCounterexamplesYesProof artifactsnot statedInput languagesUPPAAL timed-automata modeling languageDeploymentself-hosted 6/8spec lines stated 7.2
06 CBMC Free planYesPaid fromnot statedVerification methodmodel-checkingSupported formalismscontractsCounterexamplesYesProof artifactsnot statedInput languagesC, C++, Java bytecode, SystemCDeploymentself-hosted 6/8spec lines stated 7.1
07 Isabelle Free planYesPaid fromnot statedVerification methoddeductiveSupported formalismstheorem-provingCounterexamplesYesProof artifactsYesInput languagesIsabelle/Isar, Isabelle/Pure, ML; executable specifications can generate SML, OCaml, Haskell, and ScalaDeploymentself-hosted 7/8spec lines stated 7.1
08 SPIN Free planYesPaid fromnot statedVerification methodmodel-checkingSupported formalismstemporal-logicCounterexamplesYesProof artifactsnot statedInput languagesPromelaDeploymentself-hosted 6/8spec lines stated 7.1
09 ACL2 Free planYesPaid fromnot statedVerification methoddeductiveSupported formalismstheorem-provingCounterexamplesYesProof artifactsYesInput languagesACL2 logic and a subset of applicative Common LispDeploymentself-hosted 7/8spec lines stated 7.0
10 Frama-C Free planYesPaid fromnot statedVerification methodhybridSupported formalismscontractsCounterexamplesYesProof artifactsnot statedInput languagesC, ACSLDeploymentself-hosted 6/8spec lines stated 6.9
11 Dafny Free planYesPaid fromnot statedVerification methoddeductiveSupported formalismscontractsCounterexamplesYesProof artifactsnot statedInput languagesDafnyDeploymentself-hosted 6/8spec lines stated 6.8
12 Lean Free plannot statedPaid fromnot statedVerification methoddeductiveSupported formalismstheorem-provingCounterexamplesnot statedProof artifactsYesInput languagesLean 4Deploymentboth 5/8spec lines stated 6.4
13 CPAchecker Free plannot statedPaid fromnot statedVerification methodhybridSupported formalismsinvariantsCounterexamplesYesProof artifactsYesInput languagesC, SV-LIBDeploymentself-hosted 6/8spec lines stated 6.3
14 HOL Light Free planYesPaid fromnot statedVerification methoddeductiveSupported formalismstheorem-provingCounterexamplesnot statedProof artifactsnot statedInput languagesOCaml; higher-order logicDeploymentself-hosted 5/8spec lines stated 6.3
15 Viper Free planYesPaid fromnot statedVerification methodhybridSupported formalismscontractsCounterexamplesYesProof artifactsnot statedInput languagesViper language; Go, Python, and Rust via front-end toolsDeploymentself-hosted 6/8spec lines stated 6.3
16 cvc5 Free plannot statedPaid fromnot statedVerification methodnot statedSupported formalismstheorem-provingCounterexamplesnot statedProof artifactsYesInput languagesSMT-LIB v2, C++, C, Java, PythonDeploymentboth 4/8spec lines stated 6.2
17 NuSMV Free planYesPaid fromnot statedVerification methodhybridSupported formalismstemporal-logicCounterexamplesYesProof artifactsnot statedInput languagesSMVDeploymentself-hosted 6/8spec lines stated 6.2
18 PRISM Free planYesPaid fromnot statedVerification methodsymbolicSupported formalismstemporal-logicCounterexamplesYesProof artifactsnot statedInput languagesPRISM language; PEPA; SBMLDeploymentself-hosted 6/8spec lines stated 6.2
19 Stainless Free planYesPaid fromnot statedVerification methoddeductiveSupported formalismscontractsCounterexamplesYesProof artifactsnot statedInput languagesScala 3Deploymentself-hosted 6/8spec lines stated 6.2
20 Boogie Free plannot statedPaid fromnot statedVerification methoddeductiveSupported formalismscontractsCounterexamplesnot statedProof artifactsnot statedInput languagesBoogie IVLDeploymentself-hosted 4/8spec lines stated 6.1
21 OpenJML Free plannot statedPaid fromnot statedVerification methoddeductiveSupported formalismscontractsCounterexamplesYesProof artifactsnot statedInput languagesJava and JMLDeploymentself-hosted 5/8spec lines stated 6.1
22 TLA+ Free plannot statedPaid fromnot statedVerification methodhybridSupported formalismsinvariantsCounterexamplesYesProof artifactsnot statedInput languagesTLA+ and PlusCalDeploymentboth 5/8spec lines stated 6.1
23 VeriFast Free plannot statedPaid fromnot statedVerification methodsymbolicSupported formalismscontractsCounterexamplesnot statedProof artifactsnot statedInput languagesC, Rust, JavaDeploymentself-hosted 4/8spec lines stated 6.1
24 Why3 Free plannot statedPaid fromnot statedVerification methoddeductiveSupported formalismscontractsCounterexamplesYesProof artifactsnot statedInput languagesWhyML, micro-C, micro-Python, MLCFG, ComaDeploymentboth 5/8spec lines stated 6.1
25 Agda Free plannot statedPaid fromnot statedVerification methoddeductiveSupported formalismstheorem-provingCounterexamplesnot statedProof artifactsnot statedInput languagesAgdaDeploymentself-hosted 4/8spec lines stated 6.0
Compare all 25 in a table
| # | Tool | Score | Free plan | From | Free plan | Paid from | Verification method | Supported formalisms |
|---|---|---|---|---|---|---|---|---|
| 1 | PVS | 7.5 | Free plan | Free | Yes | — | hybrid | theorem-proving |
| 2 | Rocq | 7.5 | Free plan | Free | Yes | — | deductive | theorem-proving |
| 3 | Z3 | 7.4 | Free plan | Free | Yes | — | — | theorem-proving |
| 4 | Alloy Analyzer | 7.2 | Free plan | Free | Yes | — | model-checking | invariants |
| 5 | UPPAAL | 7.2 | Free plan | Free | Yes | — | model-checking | invariants |
| 6 | CBMC | 7.1 | Free plan | Free | Yes | — | model-checking | contracts |
| 7 | Isabelle | 7.1 | Free plan | Free | Yes | — | deductive | theorem-proving |
| 8 | SPIN | 7.1 | Free plan | Free | Yes | — | model-checking | temporal-logic |
| 9 | ACL2 | 7.0 | No | — | Yes | — | deductive | theorem-proving |
| 10 | Frama-C | 6.9 | No | — | Yes | — | hybrid | contracts |
| 11 | Dafny | 6.8 | No | — | Yes | — | deductive | contracts |
| 12 | Lean | 6.4 | No | — | — | — | deductive | theorem-proving |
| 13 | CPAchecker | 6.3 | No | — | — | — | hybrid | invariants |
| 14 | HOL Light | 6.3 | No | — | Yes | — | deductive | theorem-proving |
| 15 | Viper | 6.3 | No | — | Yes | — | hybrid | contracts |
| 16 | cvc5 | 6.2 | No | — | — | — | — | theorem-proving |
| 17 | NuSMV | 6.2 | No | — | Yes | — | hybrid | temporal-logic |
| 18 | PRISM | 6.2 | No | — | Yes | — | symbolic | temporal-logic |
| 19 | Stainless | 6.2 | No | — | Yes | — | deductive | contracts |
| 20 | Boogie | 6.1 | No | — | — | — | deductive | contracts |
| 21 | OpenJML | 6.1 | No | — | — | — | deductive | contracts |
| 22 | TLA+ | 6.1 | No | — | — | — | hybrid | invariants |
| 23 | VeriFast | 6.1 | No | — | — | — | symbolic | contracts |
| 24 | Why3 | 6.1 | No | — | — | — | deductive | contracts |
| 25 | Agda | 6.0 | No | — | — | — | deductive | theorem-proving |
Is your tool on this list?
Numbered spots on this list can be sponsored, and a sponsored row is labelled as paid.
Questions about this list
Which formal verification tool is ranked first on Specifiction?
PVS is ranked #1 of 33 with a score of 7.5. Rocq is second and Z3 third.
How many of these have a free plan?
8 of the 25 on this page publish a free plan on their own pricing pages.
How is this list ranked?
Ranked on what each maker publishes, the fullest spec sheet first: how deeply the product is documented, the platforms it runs on, a free tier or trial to test it, and its standing.
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