Static Analyzer for Solidity

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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 additional configuration, see the usage documentation.

Use solc-select if your contracts require older versions of solc.


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

See the Detectors Documentation for more information. By default, all the detectors are run.

Check out Crytic to get access to additional Slither's detectors and GitHub integration.


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 3.6+ and solc, the Solidity compiler.

Using Pip

pip3 install slither-analyzer

Using Git

git clone && cd slither
python3 install

We recommend using an 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.


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

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