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Slither, the Solidity source analyzer


Build Status Slack Status PyPI version

Slither is a Solidity static analysis framework written in Python 3. It runs a suite of vulnerability detectors, prints visual information about contract details, and provides an API to easily write custom analyses. Slither enables developers to find vulnerabilities, enhance their code comprehension, and quickly prototype custom analyses.


  • Detects vulnerable Solidity code with low false positives (see the list of trophies)
  • Identifies where the error condition occurs in the source code
  • Easily integrates into continuous integration and Truffle builds
  • Built-in 'printers' quickly report crucial contract information
  • Detector API to write custom analyses in Python
  • Ability to analyze contracts written with Solidity >= 0.4
  • Intermediate representation (SlithIR) enables simple, high-precision analyses
  • Correctly parses 99.9% of all public Solidity code
  • Average execution time of less than 1 second per contract

Bugs and Optimizations Detection

Run Slither on a Truffle/Embark/Dapp/Etherlime/Hardhat application:

slither .

Run Slither on a single file:

slither tests/uninitialized.sol


  • For GitHub action integration, use slither-action.
  • To generate a Markdown report, use slither [target] --checklist.
  • To generate a Markdown with GitHub source code highlighting, use slither [target] --checklist --markdown-root (replace ORG, REPO, COMMIT)

Use solc-select if your contracts require older versions of solc. For additional configuration, see the usage documentation.


Num Detector What it Detects Impact Confidence
1 abiencoderv2-array Storage abiencoderv2 array High High
2 arbitrary-send-erc20 transferFrom uses arbitrary from High High
3 array-by-reference Modifying storage array by value High High
4 incorrect-shift The order of parameters in a shift instruction is incorrect. High High
5 multiple-constructors Multiple constructor schemes High High
6 name-reused Contract's name reused High High
7 protected-vars Detected unprotected variables High High
8 public-mappings-nested Public mappings with nested variables High High
9 rtlo Right-To-Left-Override control character is used High High
10 shadowing-state State variables shadowing High High
11 suicidal Functions allowing anyone to destruct the contract High High
12 uninitialized-state Uninitialized state variables High High
13 uninitialized-storage Uninitialized storage variables High High
14 unprotected-upgrade Unprotected upgradeable contract High High
15 arbitrary-send-erc20-permit transferFrom uses arbitrary from with permit High Medium
16 arbitrary-send-eth Functions that send Ether to arbitrary destinations High Medium
17 controlled-array-length Tainted array length assignment High Medium
18 controlled-delegatecall Controlled delegatecall destination High Medium
19 delegatecall-loop Payable functions using delegatecall inside a loop High Medium
20 msg-value-loop msg.value inside a loop High Medium
21 reentrancy-eth Reentrancy vulnerabilities (theft of ethers) High Medium
22 storage-array Signed storage integer array compiler bug High Medium
23 unchecked-transfer Unchecked tokens transfer High Medium
24 weak-prng Weak PRNG High Medium
25 domain-separator-collision Detects ERC20 tokens that have a function whose signature collides with EIP-2612's DOMAIN_SEPARATOR() Medium High
26 enum-conversion Detect dangerous enum conversion Medium High
27 erc20-interface Incorrect ERC20 interfaces Medium High
28 erc721-interface Incorrect ERC721 interfaces Medium High
29 incorrect-equality Dangerous strict equalities Medium High
30 locked-ether Contracts that lock ether Medium High
31 mapping-deletion Deletion on mapping containing a structure Medium High
32 shadowing-abstract State variables shadowing from abstract contracts Medium High
33 tautology Tautology or contradiction Medium High
34 write-after-write Unused write Medium High
35 boolean-cst Misuse of Boolean constant Medium Medium
36 constant-function-asm Constant functions using assembly code Medium Medium
37 constant-function-state Constant functions changing the state Medium Medium
38 divide-before-multiply Imprecise arithmetic operations order Medium Medium
39 reentrancy-no-eth Reentrancy vulnerabilities (no theft of ethers) Medium Medium
40 reused-constructor Reused base constructor Medium Medium
41 tx-origin Dangerous usage of tx.origin Medium Medium
42 unchecked-lowlevel Unchecked low-level calls Medium Medium
43 unchecked-send Unchecked send Medium Medium
44 uninitialized-local Uninitialized local variables Medium Medium
45 unused-return Unused return values Medium Medium
46 incorrect-modifier Modifiers that can return the default value Low High
47 shadowing-builtin Built-in symbol shadowing Low High
48 shadowing-local Local variables shadowing Low High
49 uninitialized-fptr-cst Uninitialized function pointer calls in constructors Low High
50 variable-scope Local variables used prior their declaration Low High
51 void-cst Constructor called not implemented Low High
52 calls-loop Multiple calls in a loop Low Medium
53 events-access Missing Events Access Control Low Medium
54 events-maths Missing Events Arithmetic Low Medium
55 incorrect-unary Dangerous unary expressions Low Medium
56 missing-zero-check Missing Zero Address Validation Low Medium
57 reentrancy-benign Benign reentrancy vulnerabilities Low Medium
58 reentrancy-events Reentrancy vulnerabilities leading to out-of-order Events Low Medium
59 timestamp Dangerous usage of block.timestamp Low Medium
60 assembly Assembly usage Informational High
61 assert-state-change Assert state change Informational High
62 boolean-equal Comparison to boolean constant Informational High
63 deprecated-standards Deprecated Solidity Standards Informational High
64 erc20-indexed Un-indexed ERC20 event parameters Informational High
65 function-init-state Function initializing state variables Informational High
66 low-level-calls Low level calls Informational High
67 missing-inheritance Missing inheritance Informational High
68 naming-convention Conformity to Solidity naming conventions Informational High
69 pragma If different pragma directives are used Informational High
70 redundant-statements Redundant statements Informational High
71 solc-version Incorrect Solidity version Informational High
72 unimplemented-functions Unimplemented functions Informational High
73 unused-state Unused state variables Informational High
74 costly-loop Costly operations in a loop Informational Medium
75 dead-code Functions that are not used Informational Medium
76 reentrancy-unlimited-gas Reentrancy vulnerabilities through send and transfer Informational Medium
77 similar-names Variable names are too similar Informational Medium
78 too-many-digits Conformance to numeric notation best practices Informational Medium
79 constable-states State variables that could be declared constant Optimization High
80 external-function Public function that could be declared external Optimization High

For more information, see


Quick Review Printers

In-Depth Review Printers

To run a printer, use --print and a comma-separated list of printers.

See the Printer documentation for the complete lists.


See the Tool documentation for additional tools.

Contact us to get help on building custom tools.

How to install

Slither requires Python 3.8+ and solc, the Solidity compiler.

Using Pip

pip3 install slither-analyzer

Using Git

git clone && cd slither
python3 install

We recommend using a Python virtual environment, as detailed in the Developer Installation Instructions, if you prefer to install Slither via git.

Using Docker

Use the eth-security-toolbox docker image. It includes all of our security tools and every major version of Solidity in a single image. /home/share will be mounted to /share in the container.

docker pull trailofbits/eth-security-toolbox

To share a directory in the container:

docker run -it -v /home/share:/share trailofbits/eth-security-toolbox

Getting Help

Feel free to stop by our Slack channel (#ethereum) for help using or extending Slither.


How do I exclude mocks or tests?

How do I fix "unknown file" or compilation issues?

  • Because slither requires the solc AST, it must have all dependencies available. If a contract has dependencies, slither contract.sol will fail. Instead, use slither . in the parent directory of contracts/ (you should see contracts/ when you run ls). If you have a node_modules/ folder, it must be in the same directory as contracts/. To verify that this issue is related to slither, run the compilation command for the framework you are using e.g npx hardhat compile. That must work successfully; otherwise, slither's compilation engine, crytic-compile, cannot generate the AST.


Slither is licensed and distributed under the AGPLv3 license. Contact us if you're looking for an exception to the terms.


Trail of Bits publication

External publications

Title Usage Authors Venue
ReJection: A AST-Based Reentrancy Vulnerability Detection Method AST-based analysis built on top of Slither Rui Ma, Zefeng Jian, Guangyuan Chen, Ke Ma, Yujia Chen CTCIS 19
MPro: Combining Static and Symbolic Analysis forScalable Testing of Smart Contract Leverage data dependency through Slither William Zhang, Sebastian Banescu, Leodardo Pasos, Steven Stewart, Vijay Ganesh ISSRE 2019
ETHPLOIT: From Fuzzing to Efficient Exploit Generation against Smart Contracts Leverage data dependency through Slither Qingzhao Zhang, Yizhuo Wang, Juanru Li, Siqi Ma SANER 20
Verification of Ethereum Smart Contracts: A Model Checking Approach Symbolic execution built on top of Slither’s CFG Tam Bang, Hoang H Nguyen, Dung Nguyen, Toan Trieu, Tho Quan IJMLC 20
Smart Contract Repair Rely on Slither’s vulnerabilities detectors Xiao Liang Yu, Omar Al-Bataineh, David Lo, Abhik Roychoudhury TOSEM 20
Demystifying Loops in Smart Contracts Leverage data dependency through Slither Ben Mariano, Yanju Chen, Yu Feng, Shuvendu Lahiri, Isil Dillig ASE 20
Trace-Based Dynamic Gas Estimation of Loops in Smart Contracts Use Slither’s CFG to detect loops Chunmiao Li, Shijie Nie, Yang Cao, Yijun Yu, Zhenjiang Hu IEEE Open J. Comput. Soc. 1 (2020)
SAILFISH: Vetting Smart Contract State-Inconsistency Bugs in Seconds Rely on SlithIR to build a storage dependency graph Priyanka Bose, Dipanjan Das, Yanju Chen, Yu Feng, Christopher Kruegel, and Giovanni Vigna S&P 22
SolType: Refinement Types for Arithmetic Overflow in Solidity Use Slither as frontend to build refinement type system Bryan Tan, Benjamin Mariano, Shuvendu K. Lahiri, Isil Dillig, Yu Feng POPL 22
Do Not Rug on Me: Leveraging Machine Learning Techniques for Automated Scam Detection Use Slither to extract tokens' features (mintable, pausable, ..) Mazorra, Bruno, Victor Adan, and Vanesa Daza Mathematics 10.6 (2022)

If you are using Slither on an academic work, consider applying to the Crytic $10k Research Prize.