npm i tx2uml


Ethereum transaction to UML sequence diagram generator

npm version

Unified Modeling Language (UML) sequence diagram generator for Ethereum transaction.

Uniswap V1 remove liquidity

See a lot more examples with different options here


The following installation assumes Node.js has already been installed which comes with Node Package Manager (NPM).

tx2uml needs Java installed as that's required by PlantUML to generate the diagrams.

To install globally so you can run tx2uml from anywhere

npm link tx2uml --only=production

To upgrade run

npm install tx2uml -g

To see which version you are using

npm ls tx2uml


Command Line Interface (CLI)

Use the -h option to see the tx2uml CLI usage options

$ tx2uml -h
Usage: tx2uml <transaction hash or comma separated list of hashes> [options]

Ethereum transaction visualizer that generates a UML sequence diagram of transaction contract calls from an Ethereum archive node and Etherscan like API.

The transaction hashes have to be in hexadecimal format with a 0x prefix. If running for multiple transactions, the comma separated list of transaction hashes must not have white spaces. eg spaces or tags.

  -V, --version                 output the version number
  -f, --outputFormat <value>    output file format. (choices: "svg", "png", "eps", "puml", default: "svg")
  -o, --outputFileName <value>  output file name. Defaults to the transaction hash.
  -u, --url <url>               URL of the archive node with trace transaction support. (default: "http://localhost:8545", env: ARCHIVE_NODE_URL)
  -n, --nodeType <value>        geth (GoEthereum), anvil, tgeth (Erigion, fka Turbo-Geth), openeth (OpenEthereum, fka Parity), nether (Nethermind), besu (Hyperledger Besu). (choices: "geth", "anvil", "tgeth", "openeth", "nether", "besu",
                                default: "geth", env: ARCHIVE_NODE_TYPE)
  -p, --noParams                Hide function params and return values. (default: false)
  -g, --noGas                   Hide gas usages. (default: false)
  -e, --noEther                 Hide ether values. (default: false)
  -l, --noLogDetails            Hide log details emitted from contract events. (default: false)
  -t, --noTxDetails             Hide transaction details like nonce, gas and tx fee. (default: false)
  -x, --noDelegates             Hide delegate calls from proxy contracts to their implementations and calls to deployed libraries. (default: false)
  -a, --noAddresses <value>     Hide calls to contracts in a list of comma separated addresses with a 0x prefix.
  -k, --etherscanKey <value>    Etherscan API key. Register your API key at https://etherscan.io/myapikey
  -c, --chain <value>           Blockchain explorer network to get source code from. (choices: "mainnet", "polygon", "bsc", "arbitrum", "ropsten", "kovan", "rinkeby", "goerli", "sepolia", default: "mainnet", env: ETH_NETWORK)
  -d, --depth <value>           Limit the transaction call depth.
  -cf, --configFile <value>     Name of the json configuration file that can override contract details like name and ABI. (default: "tx_config.json")
  -v, --verbose                 run with debugging statements. (default: false)
  -h, --help                    display help for command

Configuration file

You can use a config file to set contract properties that are not available on chain or on Etherscan. For example, the contract's name and protocol. The config file can also be used to supply contract ABIs if a contract has not been verified on Etherscan. This is particularly useful if you are testing on a local fork of mainnet and some of the contracts in the transaction are yet to be deployed on mainnet.

The config file is in json format and has json schema config.schema.json. The config file is an object with an address property for each contract.

The default file is tx.config.json in the current working folder, but you can set the location and name of the config file with the -cf, --configFile <value> option.

An example config file

  "0xd6ed651CfDf7778794649FfA87557EF091DfFE81": {
    "protocolName": "mStable",
    "contractName": "Convex3CrvVault",
    "tokenSymbol": "mv3CRV",
    "tokenName": "Convex 3Crv Vault",
    "abi": [
  "0xaF94d5585CCCb04afcf98cA49E60F09f96f6444d": {
    "protocolName": "mStable",
    "contractName": "CurveMetapoolCalculatorLibrary"




The participant names are shortened contract addresses. Basically, the first and last 2 bytes in hexadecimal format with a 0x prefix.

Stereotypes are added for the contract and token name if they can be sourced. The contract name comes from Etherscan's verified contracts. The token name comes from Alethio.


There are five types of messages

  • Call is a solid or dotted line with a filled arrow head at the to contract.
  • Return is a dotted line with a filled arrow head at the from contract.
  • Delegate is a solid or dotted line with an open arrow head at the to contract.
  • Create is a filled line with a filled arrow head and a circle at the contract being created.
  • Selfdestruct is a solid line with a half filled arrow head looping back on itself with a Self-Destruct label.

Call and delegate messages with a dotted line are proxy calls that uses the calling contract's fallback function.

Delegate Calls

A delegatecall allows code to be executed on a contract in the context of the calling contract. That is, the delegated code appears as if it is running on the caller's contract. This means it has access to the caller's storage, Ether and calls will appear to come from the caller. Examples of delegate calls are proxy contracts calling their implementations or calls to library contracts.

In the sequence diagram, the lifeline of the delegated call will be in blue and calls will come from the calling contract. In the below example, the third call is the delegate call to the 0x3333..4444 contract. Although the code is executed on the 0x3333..4444 contract, the context is from 0x2222..3333 so the two calls to 0x4444..5555 are shown in blue and are from 0x2222..3333.

The -x or --noDelegates option can be used to hide all delegate calls.

Delegate example

Data Source

Archive node that supports tracing transactions

tx2uml needs an Ethereum archive node that supports the debug_traceTransaction or trace_transaction JSON RPC APIs.

The ethereum node url can be set with the -u or --url options or by exporting the ARCHIVE_NODE_URL environment variable. For example

export ARCHIVE_NODE_URL=https://api.archivenode.io/<your API key>/turbogeth 

Known Ethereum node clients that support debug_traceTransaction are:

tx2uml will use --nodeType geth as it's default option.

You can test if your node supports debug_traceTransaction with the following curl command

curl --location --request POST 'https://your.node.url/yourApiKey' \
--header 'Content-Type: application/json' \
--data-raw '{
    "params":["0xe5e35ee13bb6326df4da89f17504a81923299d4986de06a019ca7856cbe76bca", {"tracer": "callTracer"}],

Known Ethereum node clients that support trace_transaction are:

You can test if your node supports trace_transaction with the following curl command

curl --location --request POST 'https://your.node.url/yourApiKey' \
--header 'Content-Type: application/json' \
--data-raw '{

Node trace transaction support

debug_traceTransaction with tracer paramXX

Ethereum API providers

Most Ethereum API providers do not provide tracing or debugging APIs as they are resource intensive on the server side.

  • ArchiveNode.io brings archive data on the Ethereum blockchain to small time developers who otherwise couldn't afford it. They offer both Nethermind and Turbo-Geth archive nodes. If you want to use one specifically, you can add either /nethermind or /turbogeth to the end of your endpoint.

  • Alchemy supports trace_transaction on their paid Growth plan.

  • QuickNode supports both trace_transaction and debug_traceTransaction on their paid plan.

  • Chainstack supports both trace_transaction and debug_traceTransaction but only on their expensive Business plan.

  • GetBlock supports trace_transaction but it just hangs when tested. It also supports debug_traceTransaction but not with the tracer option required by tx2uml.

  • WatchData supports trace_transaction but I could not get it to work. No response from support. It probably needs a paid plan.

  • InfStones supports both trace_transaction and debug_traceTransaction on their paid plan.

  • Moralis supports both trace_transaction and debug_traceTransaction on their paid plan.

  • Infura does not support tracing or debugging transactions.


Etherscan is used to get the Application Binary Interfaces (ABIs) for the contracts used in a transaction. Etherscan's get contract ABI API is used with module contract and action getsourcecode. For example https://api.etherscan.io/api?module=contract&action=getsourcecode&address=0xBB9bc244D798123fDe783fCc1C72d3Bb8C189413


PlantUML is a Java program that can convert Plant UML syntax into png, svg or eps images. tx2uml pipes the PlantUML to the spawned Java process which then pipes the image outputs to a file.

plantuml.jar version 1.2021.8 is currently shipped in the lib folder.

See Recent changes for PlantUML's release notes.


PlantText is an online tool that generates diagrams from PlantUML.

PlantUML extension for VS Code

Jebbs PlantUML extension for VS Code is used to authoring the PlantUML diagrams.

Alt-D on Windows, or Option-D on Mac, to stat PlantUML preview in VS Code.

Generate png files form puml

The following will generate png files for the above examples.

java -jar ./lib/plantuml.jar ./examples/syntax.puml ./examples/delegate.puml

UML Syntax

Good online resources for learning UML

Similar transaction visualisation tools



If you want to run all the tests, you'll need to export the following environment variables which are used by the tests to connect to different archive nodes. If you are using Archive Node, you need to replace with the API key provided to you.

export ARCHIVE_NODE_URL=https://api.archivenode.io/<your api key>/nethermind
export NETHERMIND_URL=https://api.archivenode.io/<your api key>/nethermind
export TURBO_GETH_URL=https://api.archivenode.io/<your api key>/turbogeth
npm run test

Note two of the tests are currently failing due to bugs TurboGeth and Nethermind bugs.


npm build and publish commands

npm run prettier:fix
npm run clean
npm run build
# make tx2uml globally available for local testing
npm link
# check all the files are included in the npm package
npm pack --dry-run
npm publish

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