A visualisation tool for Solidity contracts featuring:
- Unified Modeling Language (UML) class diagram generator for Solidity contracts.
- Contract storage layout diagrams.
UML class diagram of Open Zeppelin's ERC20 token contracts generated from version 4.7.3 
See more contract diagrams here.
Storage layout diagram of USDC's verified source code on Etherscan. 
See an explanation of how storage diagrams work with lots of examples here.
The following installation assumes Node.js has already been installed which comes with Node Package Manager (NPM). sol2uml works with node 14 or above.
To install globally so you can run sol2uml from anywhere
npm link sol2uml --only=productionTo upgrade run
npm upgrade sol2uml -gTo see which version you are using
npm ls sol2uml -gUsage: sol2uml [command] <options> Generate UML class or storage diagrams from local Solidity code or verified Solidity code on Etherscan-like explorers. Can also flatten or compare verified source files on Etherscan-like explorers. Options: -sf, --subfolders <value> number of subfolders that will be recursively searched for Solidity files. (default: all) -f, --outputFormat <value> output file format. (choices: "svg", "png", "dot", "all", default: "svg") -o, --outputFileName <value> output file name -i, --ignoreFilesOrFolders <filesOrFolders> comma separated list of files or folders to ignore -n, --network <network> Ethereum network (choices: "mainnet", "goerli", "sepolia", "polygon", "arbitrum", "avalanche", "bsc", "crono", "fantom", "moonbeam", "optimism", "gnosis", "celo", default: "mainnet", env: ETH_NETWORK) -k, --apiKey <key> Blockchain explorer API key. eg Etherscan, Arbiscan, Optimism, BscScan, CronoScan, FTMScan, PolygonScan or SnowTrace API key (env: SCAN_API_KEY) -bc, --backColor <color> Canvas background color. "none" will use a transparent canvas. (default: "white") -sc, --shapeColor <color> Basic drawing color for graphics, not text (default: "black") -fc, --fillColor <color> Color used to fill the background of a node (default: "gray95") -tc, --textColor <color> Color used for text (default: "black") -v, --verbose run with debugging statements (default: false) -V, --version output the version number -h, --help display help for command Commands: class [options] <fileFolderAddress> Generates a UML class diagram from Solidity source code. storage [options] <fileFolderAddress> Visually display a contract's storage slots. WARNING: sol2uml does not use the Solidity compiler so may differ with solc. A known example is fixed-sized arrays declared with an expression will fail to be sized. flatten <contractAddress> Merges verified source files for a contract from a Blockchain explorer into one local file. In order for the merged code to compile, the following is done: 1. pragma solidity is set using the compiler of the verified contract. 2. All pragma solidity lines in the source files are commented out. 3. File imports are commented out. 4. "SPDX-License-Identifier" is renamed to "SPDX--License-Identifier". 5. Contract dependencies are analysed so the files are merged in an order that will compile. diff [options] <addressA> <addressB> Compare verified Solidity code differences between two contracts. The results show the comparison of contract A to B. The green sections are additions to contract B that are not in contract A. The red sections are removals from contract A that are not in contract B. The line numbers are from contract B. There are no line numbers for the red sections as they are not in contract B. help [command] display help for command Usage: sol2uml class [options] <fileFolderAddress> Generates a UML class diagram from Solidity source code. Arguments: fileFolderAddress file name, folder(s) or contract address. When a folder is used, all *.sol files in that folder and all sub folders are used. A comma-separated list of files and folders can also be used. For example sol2uml contracts,node_modules/openzeppelin-solidity If an Ethereum address with a 0x prefix is passed, the verified source code from Etherscan will be used. For example sol2uml 0x79fEbF6B9F76853EDBcBc913e6aAE8232cFB9De9 Options: -b, --baseContractNames <value> only output contracts connected to these comma separated base contract names -d, --depth <value> depth of connected classes to the base contracts. 1 will only show directly connected contracts, interfaces, libraries, structs and enums. (default: all) -c, --clusterFolders cluster contracts into source folders (default: false) -hv, --hideVariables hide variables from contracts, interfaces, structs and enums (default: false) -hf, --hideFunctions hide functions from contracts, interfaces and libraries (default: false) -hp, --hidePrivates hide private and internal attributes and operators (default: false) -hm, --hideModifiers hide modifier functions from contracts (default: false) -ht, --hideEvents hide events from contracts, interfaces and libraries (default: false) -hc, --hideConstants hide file level constants (default: false) -hx, --hideContracts hide contracts (default: false) -he, --hideEnums hide enum types (default: false) -hs, --hideStructs hide data structures (default: false) -hl, --hideLibraries hide libraries (default: false) -hi, --hideInterfaces hide interfaces (default: false) -ha, --hideAbstracts hide abstract contracts (default: false) -hn, --hideFilename hide relative path and file name (default: false) -s, --squash squash inherited contracts to the base contract(s) (default: false) -hsc, --hideSourceContract hide the source contract when using squash (default: false) -h, --help display help for command Usage: sol2uml storage [options] <fileFolderAddress> Visually display a contract's storage slots. WARNING: sol2uml does not use the Solidity compiler so may differ with solc. A known example is fixed-sized arrays declared with an expression will fail to be sized. Arguments: fileFolderAddress file name, folder(s) or contract address. When a folder is used, all *.sol files in that folder and all sub folders are used. A comma-separated list of files and folders can also be used. For example sol2uml contracts,node_modules/openzeppelin-solidity If an Ethereum address with a 0x prefix is passed, the verified source code from Etherscan will be used. For example sol2uml 0x79fEbF6B9F76853EDBcBc913e6aAE8232cFB9De9 Options: -c, --contract <name> Contract name in the local Solidity files. Not needed when using an address as the first argument as the contract name can be derived from Etherscan. -cf, --contractFile <filename> Filename the contract is located in. This can include the relative path to the desired file. -d, --data Gets the values in the storage slots from an Ethereum node. (default: false) -s, --storage <address> The address of the contract with the storage values. This will be different from the contract with the code if a proxy contract is used. This is not needed if `fileFolderAddress` is an address and the contract is not proxied. -u, --url <url> URL of the Ethereum node to get storage values if the `data` option is used. (default: "http://localhost:8545", env: NODE_URL) -bn, --block <number> Block number to get the contract storage values from. (default: "latest") -a, --array <number> Number of slots to display at the start and end of arrays. (default: "2") -hv, --hideValue Hide storage slot value column. (default: false) -h, --help display help for command Usage: sol2uml flatten <contractAddress> Merges verified source files for a contract from a Blockchain explorer into one local Solidity file. In order for the merged code to compile, the following is done: 1. pragma solidity is set using the compiler of the verified contract. 2. All pragma solidity lines in the source files are commented out. 3. File imports are commented out. 4. "SPDX-License-Identifier" is renamed to "SPDX--License-Identifier". 5. Contract dependencies are analysed so the files are merged in an order that will compile. Arguments: contractAddress Contract address in hexadecimal format with a 0x prefix. Options: -h, --help display help for command Usage: sol2uml diff [options] <addressA> <addressB> Compare verified Solidity code differences between two contracts. The results show the comparison of contract A to B. The green sections are additions to contract B that are not in contract A. The red sections are removals from contract A that are not in contract B. The line numbers are from contract B. There are no line numbers for the red sections as they are not in contract B. Arguments: addressA Contract address in hexadecimal format with a 0x prefix of the first contract. addressB Contract address in hexadecimal format with a 0x prefix of the second contract. Options: -l, --lineBuffer <value> Minimum number of lines before and after changes (default: "4") -s, --saveFiles Save the flattened contract code to the filesystem. The file names will be the contract address with a .sol extension. (default: false) -h, --help display help for command To generate a diagram of all contracts under the contracts folder and its sub folders
sol2uml class ./contractsTo generate a diagram of EtherDelta's contract from the verified source code on Etherscan. The output will be a svg file 0x8d12A197cB00D4747a1fe03395095ce2A5CC6819.svg in the working folder.
sol2uml class 0x8d12A197cB00D4747a1fe03395095ce2A5CC6819To generate a diagram of EtherDelta's contract from the verified source code on Etherscan Ropsten. The output will be a svg file 0xa19833bd291b66aB0E17b9C6d46D2Ec5fEC15190.svg in the working folder.
sol2uml class 0xa19833bd291b66aB0E17b9C6d46D2Ec5fEC15190 -n ropstenTo generate all Solidity files under some root folder and output the svg file to a specific location
sol2uml class path/to/contracts/root/folder -o ./outputFile.svgTo generate a diagram of all contracts in a single Solidity file, the output file in png format to output file ./someFile.png
sol2uml class path/to/contracts/root/folder/solidity/file.sol -f png -o ./someFile.pngTo generate a diagram of all Solidity files under the contracts and node_modules/@openzeppelin folders. The output will be contracts.svg and contracts.png files in the working folder.
sol2uml class ./contracts,node_modules/@openzeppelin -f all -vTo generate a diagram of all Solidity files under the working folder ignoring and files under the solparse, @solidity-parser and ethlint folders, which will be under the node_modules folder.
sol2uml class -i solparse,@solidity-parser,ethlintGood online resources for learning UML
A Solidity variable becomes an attribute in UML and a Solidity function becomes an operation in UML.
- Interface
- Abstract - if any of the contract's functions are abstract, the class will have an Abstract stereotype. Child contracts of abstract contracts that do not implement all the abstract functions are currently not marked as Abstract.
- Library
- event
- modifier
- abstract - if there is no function body on a contract, the operator is marked as abstract. Operators on an Interface do not have an abstract stereotype as all operators are abstract.
- fallback - abstract fallback functions will just have an abstract stereotype.
- payable - payable fallback functions will just have a fallback stereotype.
Lines:
- Solid lines for
- link the contract types of storage (state) variables. This can be linked to contracts, interfaces, libraries or file level structs and enums.
- generalisations of contracts and abstract contracts.
- aggregated contract level structs and enums.
- Dashed lines for
- generalisations of interfaces.
- types of memory variables.
Heads/Tails:
- An empty triangle head for generalisations of contracts, interfaces and abstract contracts.
- An open arrow head for storage or memory variable dependencies
- A diamond tail for aggregations of contract level structs and enums
See more storage slot diagrams here.
The colors use by the diagrams can be configured using the backColor, shapeColor, fillColor and textColor options. sol2uml uses the X11 color scheme for named colors. Other color formats like Red-Green-Blue (RGB) can also be used. For example, #ffffff for white and #000000 for black. See Graphviz color documentation for more details.
Here's an example using the color options
sol2uml storage -sc deeppink -tc #ffffff -fc dimgrey -bc black 0xfCc00A1e250644d89AF0df661bC6f04891E21585 
The biggest change with 2.x is the introduction of subcommands as sol2uml can now draw contract storage diagrams.
See version 2.x for a list of changes from 1.x.
To build the test contracts in this repository, run the following. This assumes you have the Solidity compiler solc installed on your machine.
npm run buildSol
To build the TypeScript files
npm run build
To run the Jest tests
npm run test
To access your local changes on your machine globally.
npm link
This is a rewrite of the Richard Ramos's solidity-diagram-gen tool which no longer works as it uses solidity-parser which cannot handle newer Solidity syntax like constructor.
sol2uml uses @solidity-parser/parser which is maintained by the Solidity tool community lead by Franco Victorio (@fvictorio). This is a fork of Federico Bond's (GitHub @federicobond) solidity-parser-antlr. The logic to generate the dot syntax has been rewritten and different UML syntax is now used to Richard Ramos's original implementation.
The Solidity language grammar is published with each major release.
The diagrams are generated using viz.js which uses Graphviz to render a Scalable Vector Graphics (SVG) file. Graphviz Online allows dot files to be edited and rendered into a SVG dynamically.