cvc5

cvc5 is a free, open-source SMT solver with a synthesis engine, suited to researchers and developers building verification workflows or solver-backed software. Its theory coverage and library APIs are strong assets; teams should weigh optional GPLv3 dependencies before incorporating it into a commercial product.

Overview

cvc5 checks whether first-order formulas are satisfiable or valid under combinations of background theories. It also offers Syntax-Guided Synthesis (SyGuS), which synthesizes functions subject to those theories. This makes it useful both as a standalone solver and as an engine embedded in another tool, rather than as a general-purpose interactive proof assistant.

The command-line program accepts SMT-LIB v2 and SyGuS-IF. Documented library APIs include C++, C, Java, and Python, with a Pythonic interface. The project names Kind 2, QMaxUSE, and TRLC among systems that use cvc5 as a backend or in verification checks.

Key features

Theory coverage and proof artifacts

cvc5 supports standardized SMT-LIB theories for arrays, bit-vectors, floating-point numbers, integer and real arithmetic, mixed-integer arithmetic, and strings, as well as nonstandard and extended theories. That range is useful for problems combining several mathematical domains. Proofs and unsatisfiable cores can help explain unsatisfiability results, an advantage when a workflow needs more than a yes-or-no answer.

Use and reliability

The project says core use without experimental options is intended to be extremely robust. It also says the small team prioritizes user-reported bugs over fuzzer bugs, a practical caveat for users who depend on support responses or want every fuzzing issue addressed first. Bug reports go to the issue tracker; questions, feature requests, and contributions go to GitHub Discussions.

Pricing

cvc5 costs free. The open-source solver can be used as a standalone tool or library, with essentially no limit on research or commercial use. There is no free trial because the software itself is free, and no paid tier or usage quota is part of the offer.

The default modified BSD license is permissive for many uses, but linking optional GPLv3 dependencies makes the combined work subject to GPLv3. Commercial teams should account for that condition when deciding which dependencies to include.

Platforms

cvc5 offers binaries and source releases for Linux, macOS, and Windows, and the project recommends prebuilt binaries for new users. It can also be used through APIs, deployed self-hosted, or tried in an online interface that runs SMT-LIB scripts. The project is a joint effort led by Stanford University and the University of Iowa.

Who it's for

Choose cvc5 if you need SMT solving across multiple theories, SyGuS, or a solver library accessible from C++, C, Java, or Python. Its standalone binary and online interface also give learners and researchers ways to run scripts without first building an application around the solver. Look elsewhere if your main need is an interactive proof assistant rather than an SMT solver and synthesis engine.

Pros and cons

• Broad theory coverage: standardized support spans arithmetic, strings, arrays, bit-vectors, and floating-point, helping with formulas that mix domains.
• Flexible integration: command-line input and four documented API languages suit both direct script use and embedding.
• Useful explanation artifacts: proofs and unsatisfiable cores can make unsatisfiability results easier to investigate.
• License condition to manage: optional GPLv3 dependencies change the combined work's license, which matters for commercial distribution.
• Small-team support tradeoff: user bugs take priority over fuzzer bugs, so fuzzing issues may receive less attention.

Alternatives

Browse formal verification tools for a wider category comparison. Consider Lean, Rocq, Z3, Boogie, HOL4, PVS, Why3, or Alloy Analyzer as alternative tools to evaluate for your needs.

Verdict

cvc5 is a strong fit for researchers and developers who need a free solver for combined-theory formulas, synthesis, or software integration. Its broad theory support and APIs are compelling reasons to choose it; the licensing effect of optional GPLv3 dependencies is the main reason commercial teams should look carefully at their dependency choices.