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A tool for inspecting and analyzing EVM based blockchains. Blockchain explorer for Ethereum networks.
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Blockchain Explorer for inspecting and analyzing EVM Chains.

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BlockScout provides a comprehensive, easy-to-use interface for users to view, confirm, and inspect transactions on all EVM (Ethereum Virtual Machine) blockchains. This includes the Ethereum main and test networks as well as Ethereum forks and sidechains.

Following is an overview of the project and instructions for getting started.

About BlockScout

BlockScout is an Elixir application that allows users to search transactions, view accounts and balances, and verify smart contracts on the entire Ethereum network including all forks and sidechains.

Currently available block explorers (i.e. Etherscan and Etherchain) are closed systems which are not independently verifiable. As Ethereum sidechains continue to proliferate in both private and public settings, transparent tools are needed to analyze and validate transactions.

The first release will include a block explorer for the POA core and Sokol test networks. Additional networks will be added in upcoming versions.


Development is ongoing. Please see the project timeline for projected milestones.

  • Open source development: The code is community driven and available for anyone to use, explore and improve.

  • Real time transaction tracking: Transactions are updated in real time - no page refresh required. Infinite scrolling is also enabled.

  • Smart contract interaction: Users can read and verify Solidity smart contracts and access pre-existing contracts to fast-track development. Support for Vyper, LLL, and Web Assembly contracts is in progress.

  • Token support: Version 1 supports ERC20 and ERC721 tokens. Future releases will support additional token types including ERC223 and ERC1155.

  • User customization: Users can easily deploy on a network and customize the Bootstrap interface.

  • Ethereum sidechain networks: Version 1 supports the POA main network and Sokol test network. Future iterations will support Ethereum mainnet, Ethereum testnets, forks like Ethereum Classic, sidechains, and private EVM networks.

Getting Started

We use Terraform to build the correct infrastructure to run BlockScout. See for details.


The development stack page contains more information about these frameworks.

Dependency Mac Linux
Erlang/OTP 21.0.4 brew install erlang Erlang Install Example
Elixir 1.7.1 ☝️ Elixir Install Example
Postgres 10.3 brew install postgresql Postgres Install Example
Node.js 10.5.0 brew install node Node.js Install Example
Automake brew install automake Automake Install Example
Libtool brew install libtool Libtool Install Example
Inotify-tools Not Required Ubuntu - apt-get install inotify-tools
GCC Compiler brew install gcc GCC Compiler Example
GMP brew install gmp Install GMP Devel

Build and Run

  1. Clone the repository.
    git clone

  2. Go to the explorer subdirectory.
    cd blockscout

  3. Set up default configurations.
    cp apps/explorer/config/dev.secret.exs.example apps/explorer/config/dev.secret.exs
    cp apps/block_scout_web/config/dev.secret.exs.example apps/block_scout_web/config/dev.secret.exs
    Linux: Update the database username and password configuration in apps/explorer/config/dev.secret.exs
    Mac: Remove the username and password fields from apps/explorer/config/dev.secret.exs

    Optional: Set up default configuration for testing.
    cp apps/explorer/config/test.secret.exs.example apps/explorer/config/test.secret.exs
    Example usage: Changing the default Postgres port from localhost:15432 if Boxen is installed.

  4. Install dependencies.
    mix do deps.get, local.rebar --force, deps.compile, compile

  5. Create and migrate database.
    mix ecto.create && mix ecto.migrate

    Note: If you have run previously, drop the previous database
    mix do ecto.drop, ecto.create, ecto.migrate

  6. Install Node.js dependencies.
    cd apps/block_scout_web/assets && npm install; cd -
    cd apps/explorer && npm install; cd -

  7. Update your JSON RPC Variant in apps/explorer/config/dev.exs and apps/indexer/config/dev.exs. For variant, enter ganache, geth, or parity

  8. Update your JSON RPC Endpoint in apps/explorer/config/dev/ and apps/indexer/config/dev/ For the variant chosen in step 7, enter the correct information for the corresponding JSON RPC Endpoint in parity.exs, geth.exs, or ganache.exs

  9. Start Phoenix Server.
    mix phx.server

Now you can visit localhost:4000 from your browser.

Additional runtime options:

  • Run Phoenix Server with IEx (Interactive Elixer)
    iex -S mix phx.server

  • Run Phoenix Server with real time indexer iex -S mix phx.server

Automating Restarts

By default blockscout does not restart if it crashes. To enable automated restarts, set the environment variable HEART_COMMAND to whatever you run to start blockscout. You can configure the heart beat timeout, which will change how long it will wait before considering the application to be unresponsive. At that point, it will kill the current blockscout and execute HEART_COMMAND. By default a crash dump is not written unless you set ERL_CRASH_DUMP_SECONDS to a positive or negative integer. See the documentation for heart for more information.

BlockScout Visual Interface

BlockScout Example

Projects Utilizing BlockScout

Configuring Ethereum Classic and other EVM Chains

Note: Most of these modifications will be consolidated into a single file in the future.

  1. Update the import file in apps/block_scout_web/assets/css/theme/_variables.scss. There are several preset css files for our supported chains which include Ethereum Classic, Ethereum Mainnet, Ropsten Testnet, Kovan Testnet, POA Core, and POA Sokol. To deploy Ethereum Classic, change the import to ethereum_classic_variables.

  2. Update the logo file in apps/block_scout_web/config/config.exs. To deploy Ethereum Classic, change this file to classic_ethereum_logo.svg.

  3. Update the check_origin configuration in apps/block_scout_web/config/prod.exs. This allows realtime events to occur on your endpoint.

  4. Update the node configuration. You will need a full tracing node with WebSockets enabled. Make the changes in the following files (dev/prod):

  • apps/explorer/config/dev/parity.exs
  • apps/explorer/config/prod/parity.exs
  • apps/indexer/config/dev/parity.exs
  • apps/indexer/config/prod/parity.exs
  1. Update the dropdown menu in the main navigation apps/block_scout_web/lib/block_scout_web/templates/layout/_topnav.html.eex

  2. Update the coin in apps/explorer/config/config.exs. This will pull relevant information from

Umbrella Project Organization

This repository is an umbrella project. Each directory under apps/ is a separate Mix project and OTP application, but the projects can use each other as a dependency in their mix.exs.

Each OTP application has a restricted domain.

Directory OTP Application Namespace Purpose
apps/ethereum_jsonrpc :ethereum_jsonrpc EthereumJSONRPC Ethereum JSONRPC client. It is allowed to know Explorer's param format, but it cannot directly depend on :explorer
apps/explorer :explorer Explorer Storage for the indexed chain. Can read and write to the backing storage. MUST be able to boot in a read-only mode when run independently from :indexer, so cannot depend on :indexer as that would start :indexer indexing.
apps/block_scout_web :block_scout_web BlockScoutWeb Phoenix interface to :explorer. The minimum interface to allow web access should go in :block_scout_web. Any business rules or interface not tied directly to Phoenix or Plug should go in :explorer. MUST be able to boot in a read-only mode when run independently from :indexer, so cannot depend on :indexer as that would start :indexer indexing.
apps/indexer :indexer Indexer Uses :ethereum_jsonrpc to index chain and batch import data into :explorer. Any process, Task, or GenServer that automatically reads from the chain and writes to :explorer should be in :indexer. This restricts automatic writes to :indexer and read-only mode can be achieved by not running :indexer.

CircleCI Updates

To monitor build status, configure your local CCMenu with the following url:



  • PhantomJS (for wallaby)

Running the tests

  1. Build the assets.
    cd apps/block_scout_web/assets && npm run build; cd -

  2. Format the Elixir code.
    mix format

  3. Run the test suite with coverage for whole umbrella project. This step can be run with different configuration outlined below. mix coveralls.html --umbrella

  4. Lint the Elixir code.
    mix credo --strict

  5. Run the dialyzer.
    mix dialyzer --halt-exit-status

  6. Check the Elixir code for vulnerabilities.
    cd apps/explorer && mix sobelow --config; cd -
    cd apps/block_scout_web && mix sobelow --config; cd -

  7. Lint the JavaScript code.
    cd apps/block_scout_web/assets && npm run eslint; cd -

  8. Test the JavaScript code.
    cd apps/block_scout_web/assets && npm run test; cd -


This is the default setup. mix coveralls.html --umbrella will work on its own, but to be explicit, use the following setup:

export ETHEREUM_JSONRPC_CASE=EthereumJSONRPC.Case.Parity.Mox
mix coveralls.html --umbrella --exclude no_parity
HTTP / WebSocket
export ETHEREUM_JSONRPC_CASE=EthereumJSONRPC.Case.Parity.HTTPWebSocket
mix coveralls.html --umbrella --exclude no_parity
Protocol URL
HTTP http://localhost:8545
WebSocket ws://localhost:8546
mix coveralls.html --umbrella --exclude no_geth
HTTP / WebSocket
mix coveralls.html --umbrella --exclude no_geth
Protocol URL
WebSocket wss://

API Documentation

To view Modules and API Reference documentation:

  1. Generate documentation.
    mix docs
  2. View the generated docs.
    open doc/index.html



All Javascript files are under apps/block_scout_web/assets/js and the main file is app.js. This file imports all javascript used in the application. If you want to create a new JS file consider creating into /js/pages or /js/lib, as follows:


This folder contains all scripts that can be reused in any page or can be used as a helper to some component.


This folder contains the scripts that are specific for some page.


This project uses Redux to control the state in some pages. There are pages that have things happening in real-time thanks to the Phoenix channels, e.g. Address page, so the page state changes a lot depending on which events it is listening. The redux is also used to load some contents asynchronous, see async_listing_load.js.

To understand how to build new pages that need redux in this project, see the redux_helpers.js


The app is currently internationalized. It is only localized to U.S. English. To translate new strings.

  1. To setup translation file.
    cd apps/block_scout_web; mix gettext.extract --merge; cd -
  2. To edit the new strings, go to apps/block_scout_web/priv/gettext/en/LC_MESSAGES/default.po.


BlockScout is setup to export Prometheus metrics at /metrics.


  1. Install prometheus: brew install prometheus
  2. Start the web server iex -S mix phx.server
  3. Start prometheus: prometheus --config.file=prometheus.yml


  1. Install grafana: brew install grafana
  2. Install Pie Chart panel plugin: grafana-cli plugins install grafana-piechart-panel
  3. Start grafana: brew services start grafana
  4. Add Prometheus as a Data Source
    1. open http://localhost:3000/datasources
    2. Click "+ Add data source"
    3. Put "Prometheus" for "Name"
    4. Change "Type" to "Prometheus"
    5. Set "URL" to "http://localhost:9090"
    6. Set "Scrape Interval" to "10s"
  5. Add the dashboards from For each *.json file in the repo.
    1. open http://localhost:3000/dashboard/import
    2. Copy the contents of the JSON file in the "Or paste JSON" entry
    3. Click "Load"
  6. View the dashboards. (You will need to click-around and use BlockScout for the web-related metrics to show up.)


Blockscout supports tracing via Spandex. Each application has its own tracer, that is configured internally to that application. In order to enable it, visit each application's config/<env>.ex and update its tracer configuration to change disabled?: true to disabled?: false. Do this for each application you'd like included in your trace data.

Currently, only Datadog is supported as a tracing backend, but more will be added soon.


If you would like to use DataDog, after enabling Spandex, set "DATADOG_HOST" and "DATADOG_PORT" environment variables to the host/port that your Datadog agent is running on. For more information on Datadog and the Datadog agent, see their documentation.


If you want to use a different backend, remove the SpandexDatadog.ApiServer Supervisor.child_spec from Explorer.Application and follow any instructions provided in Spandex for setting up that backend.

Memory Usage

The work queues for building the index of all blocks, balances (coin and token), and internal transactions can grow quite large. By default, the soft-limit is 1 GiB, which can be changed in apps/indexer/config/config.exs:

config :indexer, memory_limit: 1 <<< 30

Memory usage is checked once per minute. If the soft-limit is reached, the shrinkable work queues will shed half their load. The shed load will be restored from the database, the same as when a restart of the server occurs, so rebuilding the work queue will be slower, but use less memory.

If all queues are at their minimum size, then no more memory can be reclaimed and an error will be logged.


We would like to thank the EthPrize foundation for their funding support.


See for contribution and pull request protocol. We expect contributors to follow our code of conduct when submitting code or comments.


License: GPL v3.0

This project is licensed under the GNU General Public License v3.0. See the LICENSE file for details.

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