No. 28 of 33 ·Formal Verification Tools

TLA+

Windows · Mac · Linux · Extension

Freedom report

Two barsScore 5.3

Free tierA free tier is on its own pricing page
Open codeNo open-source code on record
Runs widely3 of 6 device platforms
DocumentedThinly documented

TLA+ is ranked #28 of 33 in formal verification tools on Freedom251. It runs on Browser extension, Linux, macOS, Windows. There is a free plan.

TLA+ plans and pricing

All plans

TLA+ Free Open-source specification language and tools · command-line tools require Java 11+ github.com · 9 Oct 2026

Compared on formal verification tools

Verification method: hybrid
Supported formalisms: invariants
Counterexamples: Yes
Input languages: TLA+ and PlusCal
Deployment: both

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The record

Purpose: TLA+ is a high-level language for modeling software and hardware systems, especially concurrent and distributed systems.
Design verification: TLA+ and its tools are intended to help find fundamental design errors that can be difficult and expensive to correct in code.
PlusCal: PlusCal describes algorithms and translates them into TLA+ models that can be checked with TLA+ tools.
Model checking: TLC checks executable TLA+ specifications for safety and liveness properties and can run across multiple computers or cloud systems.
Proof checking: TLAPS mechanically checks proofs written in TLA+.
IDE features: The TLA+ Toolbox supports editing specifications, running the PlusCal translator and TLC, exploring error traces, and running the proof system.
Platforms: The Toolbox download instructions cover Windows, Mac OS, and Linux.
Editor integration: A Visual Studio Code extension supports TLA+ and PlusCal syntax highlighting, translation, parsing, TLC runs, result visualization, code completion, and formatting.
Command line and Java: The tools can run from the command line using tla2tools.jar and require Java 11 or later.
License: The TLA+ tools and Toolbox repository is licensed under the MIT License.
Toolbox maintenance: The repository describes the Eclipse-based Toolbox GUI as currently unmaintained.
Known limitations: The Toolbox page notes that it has minor unfixed bugs and that its help pages are its only user manual.
Support: The TLA+ Foundation directs technical questions and issues to the appropriate GitHub issue tracker.
Price from: Free

Where it ranks on Freedom251

Best Formal Verification Tools in 2026#28 of 33

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Sources

lamport.azurewebsites.net/tla/tla.html· checked 9 Oct 2026
lamport.azurewebsites.net/tla/high-level-view.html· checked 9 Oct 2026
lamport.azurewebsites.net/tla/tools.html· checked 9 Oct 2026
lamport.azurewebsites.net/tla/toolbox.html· checked 9 Oct 2026
marketplace.visualstudio.com/items· checked 9 Oct 2026
github.com/tlaplus/tlaplus/blob/master/README.md· checked 9 Oct 2026
github.com/tlaplus/tlaplus· checked 9 Oct 2026
foundation.tlapl.us· checked 9 Oct 2026