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Apalache

Free#32 of 35 in Formal Verification Tools

Apalache: An open-source, SMT-backed checker for bounded TLA+ analysis and counterexample traces. Ranked #32 of 35 in Formal Verification Tools by our editors (6.3/10); pricing: Open source; best for SMT-backed bounded TLA+ analysis.

6.3/10★★★☆☆Editor score

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At a glance

• Editor score
  6.3 / 10
• Pricing
  Open source
• Best for
  SMT-backed bounded TLA+ analysis
• Paid from
  Free
• Verification method
  Symbolic
• Facts checked
  20 Sep 2026

• Where it wins

  • Translates TLA+ specifications into Microsoft Z3 and CVC5 logic
  • Checks bounded executions, inductiveness, and temporal properties
  • Generates explicit counterexample traces for violated properties

• Where it doesn't

  • Focused on self-hosted and API deployment
  • Bounded analysis runs only up to a specified execution length
  • Requires familiarity with TLA+, SMT solvers, and formal invariants

Our verdict on Apalache

Apalache is an open-source symbolic model checker for TLA+ specifications, aimed at technical teams working with formal specifications. It translates TLA+ into logic supported by SMT solvers, including Microsoft Z3 and CVC5, then analyzes executions and properties through symbolic methods. The tool supports TLA+ and Quint inputs, checks state, action, temporal, trace, and inductive invariants, and can produce explicit counterexample traces when properties fail. Its best fit is teams that want bounded TLA+ analysis with solver-backed reasoning rather than a general-purpose verification environment.

Its verification depth is broad within that focus. Apalache supports randomized symbolic execution up to a specified length, bounded model checking of executions, and inductiveness checking for invariants. Temporal operators including always, eventually, and leads-to are supported, which extends its use beyond simple state assertions. The JSON-RPC server also supports exploration scripts, while integrations with Quint, Solarkraft, and Atomkraft can fit workflows built around related formal-methods tools. These capabilities make it useful when understanding a failed property requires a concrete trace rather than only a pass-or-fail result.

Deployment is oriented toward technical, self-managed environments. Apalache is available as a prebuilt package, Docker image, or source build, and its listed platforms are API and self-hosted. The open-source model suits teams that want to inspect, deploy, and integrate the checker within their own workflow. Teams needing a managed product, a broader deployment model, or AI-assisted features should consider another option. Choose Apalache for SMT-backed exploration of TLA+ specifications and bounded properties; avoid it when those requirements do not match your verification process.

Your product? Our editors can test Apalache in depth and publish a review, labelled as paid · from $149/mo →

Apalache pricing

Apalache fact sheet

Apalache integrations

Apalache lists 5 integrations on its own site.

• Microsoft Z3
• CVC5
• Quint
• Solarkraft
• Atomkraft

Alternatives to Apalache

• IIsabelleA 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
• PPVSA broad, self-hosted environment for hybrid formal verification workflows.9.2

See all Apalache alternatives →

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Featured on iTechGuides

Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026

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Last updated 7 Oct 2026 · How we research and update