A head-to-head comparison of Foundry and Slither — pricing, the features that actually differ, and which one fits which use case.
Blazing-fast Rust-based Solidity testing framework with built-in fuzzing and invariant testing
Trail of Bits' open-source static analysis framework for Solidity — catches vulnerabilities before auditors do
These are the 9 capabilities where the two tools genuinely diverge — the rest of their feature sets overlap.
| Capability | Foundry | Slither |
|---|---|---|
| Local Node | Yes | No |
| Mainnet Forking | Yes | — |
| Language | Solidity (tests) | Solidity |
| Test Framework | forge-std | N/A (analysis tool) |
| Plugin Ecosystem | Growing (smaller than Hardhat) | slitherin + custom detectors |
| Debugging | Yes | No |
| Deployment System | Forge scripts | N/A |
| Fuzz Testing | Yes | No |
| Invariant Testing | Yes | — |
| Feature | Foundry | Slither |
|---|---|---|
| Local Node | ✓ | ✗ |
| Mainnet Forking | ✓ | — |
| Language | Solidity (tests) | Solidity |
| Test Framework | forge-std | N/A (analysis tool) |
| Plugin Ecosystem | Growing (smaller than Hardhat) | slitherin + custom detectors |
| Debugging | ✓ | ✗ |
| Deployment System | Forge scripts | N/A |
| Open Source | ✓ | ✓ |
| Fuzz Testing | ✓ | ✗ |
| Invariant Testing | ✓ | — |
| Static Analysis | — | ✓ |
| Ci Cd Ready | — | ✓ |
Both tools are free to use — costs come from network or usage fees.
Foundry
Free
Slither
Free
Watch out: Smaller plugin ecosystem than Hardhat — some tooling requires custom solutions.
Watch out: False positive rate requires review — not all flagged issues are real vulnerabilities.
Foundry edges ahead on our editorial score (4.8/5), but these tools aren’t straight substitutes. Pick Foundry when 5–20x faster test execution than hardhat — critical for large suites and audit pipelines matters most to your workflow; pick Slither when 80+ vulnerability detectors catch reentrancy, access control, and overflow issues before deployment is the priority. The deciding factor is usually the trade-off you can least afford — Foundry means accepting that smaller plugin ecosystem than hardhat — some tooling requires custom solutions, while Slither means false positive rate requires review — not all flagged issues are real vulnerabilities.
Foundry carries the higher editorial rating (4.8/5 vs 4.6/5), but they solve different problems. Foundry is the stronger pick when you need 5–20x faster test execution than hardhat — critical for large suites and audit pipelines. Slither wins when 80+ vulnerability detectors catch reentrancy, access control, and overflow issues before deployment.
Both tools are free to use, with costs coming from network or usage fees rather than subscriptions.
Foundry's main limitation is that smaller plugin ecosystem than hardhat — some tooling requires custom solutions. For Slither, false positive rate requires review — not all flagged issues are real vulnerabilities. Weigh these against how you actually plan to use the tool.
In most cases yes — many teams run both, using each where it's strongest. Since Foundry leads on 5–20x faster test execution than hardhat — critical for large suites and audit pipelines and Slither on 80+ vulnerability detectors catch reentrancy, access control, and overflow issues before deployment, the two are often complementary rather than mutually exclusive.