A blockchain explorer is a search engine and visualization tool for public blockchain data. Because most blockchains store data in binary or cryptographic formats that are difficult for humans to parse directly, explorers decode and display this data in a searchable, human-readable format. Anyone can look up any transaction, address, block, or smart contract on a public blockchain using an explorer — no account required. This transparency is fundamental to public blockchains’ trust model.
What You Can Do With a Block Explorer
| Function | Description |
|---|---|
| Transaction lookup | Enter a transaction hash (TXID) to see status (confirmed/pending), amount, timestamp, fees, from/to addresses |
| Address lookup | View full transaction history, current balance, and token holdings for any wallet address |
| Block viewer | Browse individual blocks: timestamp, miner/validator, transactions included, size, gas used |
| Smart contract inspection | View deployed contract code (if verified), read public state variables, see all interactions |
| Token tracker | View all holders of a specific token, transaction history, contract details |
| Gas tracker | Current network gas prices, estimated confirmation times at different fee levels |
| Token approvals | Check which smart contracts have spending permissions on a wallet’s tokens |
Major Explorers by Chain
Bitcoin
|———-|—–|———|
| Blockstream Explorer | blockstream.info | Open source, no JavaScript required, Lightning Network support |
| Mempool.space | mempool.space | Real-time mempool visualization, fee estimation, UTXO model tools |
| Blockchain.com Explorer | blockchain.com/explorer | Most widely known consumer-facing Bitcoin explorer |
| BTCScan | btcscan.org | Lightweight, minimal UI |
Ethereum
|———-|—–|
| Etherscan | etherscan.io — gold standard for EVM chains |
| Otterscan | Open-source local Etherscan alternative |
| Blockchair | Multi-chain explorer including Ethereum |
Ethereum L2s / EVM Chains
|——-|———|
| Arbitrum | arbiscan.io |
| Optimism | optimistic.etherscan.io |
| Base | basescan.org |
| Polygon | polygonscan.com |
| BNB Chain | bscscan.com |
| Avalanche | snowtrace.io |
Other Chains
|——-|———|
| Solana | solscan.io, explorer.solana.com |
| Cardano | cardanoscan.io |
| Polkadot | polkadot.subscan.io |
| Cosmos | mintscan.io |
| Tron | tronscan.org |
| Near | explorer.near.org |
How Explorers Work Technically
Block explorers run a full node (or connect to one) and index the blockchain into a database optimized for fast lookup queries. The indexed data is then served through a web interface and API. Process:
- Node syncs with the blockchain in real time
- Each block’s transactions are decoded and stored in a relational/document database
- Indexes are built for addresses, transaction hashes, block numbers
- Web UI and REST API serve queries against this indexed data
Because running a full archive node (storing all historical state) for chains like Ethereum requires significant storage (multiple terabytes), most explorers run on specialized infrastructure.
On-Chain Investigation Use Cases
Blockchain explorers are used extensively for:
- Due diligence: Verify wallet claims (“I hold 100 BTC” — check the address)
- Hack tracing: Trace stolen funds across wallets in real time
- Exchange transparency: Verify exchange proof-of-reserves claims
- Smart contract review: Check contract code and verify audit claims
- Token holder analysis: Distribution of a token across wallets
- Defi analytics: TVL changes, protocol interactions, LP positions
Research
- Nakamoto, S. (2008). “Bitcoin: A Peer-to-Peer Electronic Cash System.” bitcoin.org/bitcoin.pdf.
- Wood, G. (2014). “Ethereum: A Secure Decentralised Generalised Transaction Ledger.” Ethereum Yellow Paper.
- Biryukov, A. et al. (2014). “Deanonymisation of Clients in Bitcoin P2P Network.” Proceedings of the 2014 ACM CCS.
- Kalodner, H. et al. (2017). “BlockSci: Design and Applications of a Blockchain Analysis Platform.” USENIX Security 2020.
- Chainalysis (2024). “Crypto Crime Report 2024.” Chainalysis Annual Report.