Open-source Ethereum explorers you can run yourself

Blockscout: the full self-hosted explorer

Blockscout started in 2018 at POA Network and now powers explorers on more than 100 chains, including eth.blockscout.com, which our own live tool reads from. It is the only project here that matches a commercial explorer feature for feature: contract verification, read and write tabs, token and NFT pages, internal transactions, blobs, EIP-7702 delegations, a REST API and an Etherscan-compatible RPC API. Our Blockscout review covers the hosted mainnet instance in depth.

The licence changed in April 2026

Many articles still call Blockscout GPL-3.0. That is only true up to backend v10.2.0 and frontend v2.7.1. From v11.0.0, released on 22 April 2026, Blockscout ships under the source-available Blockscout Software License. Self-hosting an explorer for your own chain, modifying it and using it internally stay free. Selling it as a hosted service, bundling it into a paid rollup-as-a-service platform or charging for deployment work now needs a commercial licence, and every interface must show a “Powered by Blockscout” credit. Forks of v10.2.0 and earlier remain under the GPL.

Self-hosting with Docker

The repository ships ready-made Docker Compose files in its docker-compose folder. You need Docker 20.10+, Compose 2.x and a running JSON-RPC client. From that folder, docker compose up starts the default stack: a PostgreSQL 17 database, Redis, the backend, the frontend, an Nginx proxy and Rust microservices for stats, the Solidity-to-UML visualizer and signature lookups. Client-specific files save you the configuration: docker compose -f erigon.yml up -d, geth.yml (also suitable for Reth), anvil.yml and hardhat-network.yml. All of them expect the node at http://localhost:8545. On Linux, bind a local node to 0.0.0.0 rather than 127.0.0.1 so the containers can reach it.

Requirements, honestly

Blockscout needs an archive node with tracing enabled, because it imports every state change and internal call. The docs recommend a 16-core, 32-thread machine with 128 GB of RAM as a base for large chains, and the database is the real bill: the project’s own estimate for indexing Ethereum mainnet is about 21,000 GiB, Sepolia about 5,200 GiB and Ethereum Classic about 555 GiB (figures from December 2024, and they only grow). For a small private network the same stack runs happily on a modest VM. For mainnet, most teams are better served by the public instance or the hosted Autoscout service. See the official hardware requirements before you order a server.

Otterscan: the local Ethereum explorer on top of your node

Otterscan takes the opposite approach. It is a React app with no database of its own. Instead, it relies on a set of custom JSON-RPC methods under the ots_ namespace, implemented inside the execution client, that return exactly the data an explorer page needs in one call. The result is an Ethereum node explorer that feels as fast as Etherscan, runs on a laptop and never sends your queries anywhere. The app is MIT-licensed; the Otterscan API inside Erigon follows Erigon’s LGPL-3.0.

Three clients speak ots_ today. Erigon has shipped it built in since v2.29.0: start it with --http.api eth,erigon,trace,ots and set --http.corsdomain so the browser can call it. Reth supports it too, by adding ots to its --http.api list. And Foundry’s Anvil implements the namespace, which makes Otterscan a superb companion for local contract work. The current release is v2.11.0 (November 2025), distributed as a Docker image:

docker run --rm -p 5100:80 --name otterscan -d --env ERIGON_URL="http://127.0.0.1:8545" otterscan/otterscan:v2.11.0

Open http://localhost:5100 and you get block and transaction pages, a very readable trace view, contract source pulled from Sourcify and method names decoded via the 4byte directory. What you do not get is anything that requires a global index, such as token holder lists or network-wide charts. For that you need Blockscout. The Otterscan repository links to the full install book.

Ethernal: an explorer built for development chains

Ethernal is an MIT-licensed explorer designed for chains you are building on rather than chains you are watching. There is a hosted version at app.tryethernal.com and a self-hosted one: clone the repository, run make start and finish configuration in the browser at /setup. Under the hood it runs a Node.js backend with PostgreSQL (TimescaleDB), Redis and a WebSocket server. It works with Hardhat, Anvil and Geth as well as OP Stack and ZK rollups, and a separate hardhat-ethernal plugin can push contract artifacts from a Hardhat project so contracts appear decoded as soon as you deploy them.

Chainlens (formerly Epirus): explorer for Besu and Quorum

Web3 Labs has renamed its explorer twice: Epirus became Sirato, and Sirato became Chainlens. The name changed, the target did not. Chainlens focuses on EVM networks in enterprise settings, especially Hyperledger Besu and GoQuorum. The free edition, chainlens-free, runs with Docker Compose or Kubernetes. Set NODE_ENDPOINT to your node and run docker-compose up; the recommended minimum is 1 CPU and 8 GB of RAM plus disk proportional to the chain. Note the licence: the free edition is for non-commercial use and evaluation, and commercial deployments need an agreement with Web3 Labs, which also sells hosted plans.

Block explorers for private Ethereum networks

Permissioned networks built on Besu or GoQuorum, usually with QBFT or IBFT 2.0 consensus, have the same explorer needs as mainnet plus one more: access control. You have two well-documented choices. The Besu documentation describes Chainlens, and its Developer Quickstart can generate a network with Chainlens already enabled using the --chainlens true option. Blockscout supports Besu as a first-class JSON-RPC variant (ETHEREUM_JSONRPC_VARIANT=besu) and ships a Compose file for Geth Clique networks. Run the node in archive mode with tracing if you want internal transactions.

Whichever you choose, remember that an explorer is a read-everything window into the ledger. On a consortium chain where confidentiality matters, put it behind your VPN or an authenticating reverse proxy rather than on the open internet. And treat the explorer’s database as sensitive, because it is a full copy of the network’s data in an easily queried form.

Explorers for local dev chains: Anvil and Hardhat

Both Foundry’s Anvil and the Hardhat node serve JSON-RPC on 127.0.0.1:8545 with chain ID 31337 by default. That makes them easy to plug into any explorer. Our order of preference: Otterscan for Anvil, because it needs no database and Anvil speaks ots_ natively; Ethernal if your team uses Hardhat and wants contracts decoded automatically; and Blockscout’s anvil.yml or hardhat-network.yml when you want to test how your dApp will look on a production-style explorer. Remember that a restarted dev chain starts from block zero, so explorers with a database need a reset too.

When you move from a local chain to a public testnet, you no longer need your own explorer. Our guide to Sepolia and Hoodi testnet explorers lists the hosted ones, and the smart contract explorer guide explains verification once you deploy.

Historic projects: Expedition and the Ethereum Lite Explorer

Expedition

Expedition was built by ETC Labs as a minimal explorer for Ethereum Classic, Ethereum and their testnets. It has no database: a TypeScript and React front end calls a JSON-RPC endpoint directly, and a ?rpcUrl= parameter lets you point it at any node, including a local one. The original etclabscore/expedition repository was archived in 2021, and the xops/expedition fork has not seen commits since 2022. The hosted expedition.dev site did not respond when we checked in September 2026. It still works as a lightweight self-hosted viewer, especially for ETC; for a maintained ETC explorer see our Ethereum Classic explorer guide.

Alethio Ethereum Lite Explorer

The Ethereum Lite Explorer was the original “explorer without a backend”: a client-side React, MobX and TypeScript app that connected to any JSON-RPC node, from Infura to Ganache or Besu, with a plugin system for extra panels. It was genuinely useful for private networks in 2019 and 2020. Alethio has since stopped operating, its GitHub organisation warns that the software is likely unmaintained, and the last tagged release is v1.0.0-beta.10 from April 2020. The MIT code is still a nice read, but we would not deploy it on a network you care about in 2026.

Which open-source explorer should you pick?

If you run your own Erigon or Reth node and want privacy, install Otterscan and stop there. If you are launching a chain, public or permissioned, and need contract verification, token pages and an API for your users, Blockscout is the standard, as long as you read the new licence if money changes hands. If your chain is a Hardhat or Anvil devnet, Ethernal or Otterscan will get you further with less setup. And for a Besu consortium that wants something working this afternoon, Chainlens via the Besu quickstart is the shortest path.

Whatever you run, your explorer is only as honest as the node behind it. A pruned node silently returns incomplete history, and a node without tracing hides internal transactions. If a number looks wrong, cross-check it against a public explorer; our ranking of the best Ethereum explorers and the explorer API comparison list the reliable ones.

Crypto assets are volatile. Only fund what you need, and check that the service is available in your country.