In computer science and mathematical logic, a proof assistant or interactive theorem prover is a software tool to assist with the development of formal proofs by human-machine collaboration. This involves some sort of interactive proof editor, or other interface, with which a human can guide the search for proofs, the details of which are stored in, and some steps provided by, a computer.
This type of software provides a formal language to write mathematical definitions, executable algorithms and theorems together with an environment for semi-interactive development of machine-checked proofs.
These software tools aid the development of formal proofs by man-machine collaboration. They offer a formal language where mathematical definitions, executable algorithms and theorems co-exist, and an interactive environment keeping the current status of the proof, and updating it according to commands (usually called tactics) issued by the user.
Here’s our verdict captured in a legendary LinuxLinks-style ratings chart. They are all free and open source software.

Let’s explore the 11 proof assistants. For each title we have compiled its own portal page, a full description with an in-depth analysis of its features, a screenshot of the software in action together with links to relevant resources.
| Proof Assistants | |
|---|---|
| Rocq Prover | Formal proof management system |
| Isabelle | Generic proof assistant; express mathematical formulas in a formal language |
| Lean | Programming language and theorem prover |
| Agda | Interactive system for writing and checking proofs |
| F* | Functional language for verified programs with dependent refinement types |
| HOL4 | Interactive higher-order logic environment for rigorous theorem development |
| Aya | Dependently typed language for formalisation and certified programming |
| Lambdapi | Logical framework for defining and checking expressive type systems |
| HOL Light | Lightweight higher-order logic system with a small trusted kernel |
| PVS | Specification and verification suite for analysing complex systems |
| LISA | Scala-based platform for formal mathematics and automated reasoning |
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