Z3
Z3: A flexible, free solver for developers building verification and analysis tools. Ranked #10 of 35 in Formal Verification Tools by our editors (8.5/10); pricing: Free plan; best for general-purpose SMT solving and APIs.
At a glance
- Editor score8.5 / 10
- PricingFree plan
- Best forGeneral-purpose SMT solving and APIs
- Free planYes
- Paid fromFree
- Facts checked20 Sep 2026
Where it wins
- Supports theorem proving, arithmetic, bit-vectors, arrays, and datatypes
- Provides models, unsat proofs, and unsat cores
- Offers APIs and bindings across many programming languages
Where it doesn't
- Designed as a low-level component rather than an end-user verification editor
- Requires integration with a verification or analysis workflow
- Self-hosted deployment places setup and maintenance responsibility on the team
Our verdict on Z3
Z3 is an open-source theorem prover and satisfiability modulo theories (SMT) solver from Microsoft Research. It is intended primarily as a low-level component for software analysis and verification tools, rather than as a standalone verification editor. Z3 suits developers and researchers who need to check logical formulas over supported theories, either through SMT-LIB2 or programming-language APIs and bindings. Its supported inputs include SMT-LIB2, C, C++, .NET, Java, Python, Rust, OCaml, Julia, JavaScript, TypeScript, Smalltalk, and Go.
The solver covers theorem proving over logical formulas and theories, arithmetic for integer and real theories, bit-vector reasoning, and array and datatype reasoning. It also supports quantifier instantiation, model construction, model generation for satisfiable formulas, unsatisfiable proof retrieval, and unsat-core retrieval. This combination makes Z3 suitable when a verification workflow needs both satisfiability results and proof-related artifacts. Teams can work with local compilation and binaries for Windows, macOS, and Linux, while browser-based JavaScript examples are available. The published platform coverage also includes web, Android, and self-hosted use.
Z3 is free and open source, so it fits teams that want a solver they can incorporate into their own tools without a commercial plan structure. The trade-off is its component-oriented design: teams selecting Z3 should be prepared to connect it to a larger software analysis or verification workflow rather than expect a complete end-user editor. It is a strong fit for general-purpose SMT solving and APIs, especially when language bindings, theorem proving, model generation, or unsat artifacts matter. Teams seeking a ready-made verification application may prefer a product built around a complete user interface instead.
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Z3 pricing
Z3 fact sheet
| Free plan | Yes |
|---|---|
| Paid from | Free |
| Verification method | Not verified |
| Supported formalisms | Theorem-proving |
| Counterexamples | Yes |
| Proof artifacts | Yes |
| Input languages | SMT-LIB2, C, C++, .NET, Java, Python, Rust, OCaml, Julia, JavaScript, TypeScript, Smalltalk, Go |
| Deployment | Self-hosted |
| Deployment | Self-hosted, Browser extension |
| Platforms | Web, Windows, macOS, Linux, Android |
| Support | Community, Docs |
| Built for | Solo, Small business, Mid-market, Enterprise (editorial estimate) |
| Pricing | Free plan |
| Website | github.com |
| Facts checked | 20 Sep 2026 |
Alternatives to Z3
- 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
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Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
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