CRYPCryptoTutorial NO. ---
How to read on-chain data on mempool.space and Etherscan
Look up a Bitcoin transaction on mempool.space and an Ethereum transfer on Etherscan without an account, then learn why a simple ETH transfer uses 21,000 gas and what active addresses, exchange flows and hash rate can and cannot show.
Key takeaways
- Learning how to read on-chain data starts with a free block explorer: mempool.space for Bitcoin and Etherscan for Ethereum let anyone look up a transaction, an address or a block without an account.
- A Bitcoin transaction spends earlier outputs (UTXOs) and creates new ones. The fee is whatever input value is not assigned to an output, and it is priced in satoshis per virtual byte (sat/vB).
- An Ethereum transaction has a sender, a recipient, a value in ETH, a nonce and gas settings. A simple ETH transfer uses 21,000 gas, and the base fee part of every fee is burned.
- Token transfers and "internal transactions" on Ethereum happen inside smart-contract calls, so they appear in separate tabs on Etherscan rather than as the headline ETH value.
- Popular metrics such as active addresses, exchange flows, fees and hash rate are estimates with known blind spots. They describe network activity; they do not predict prices.
To learn how to read on-chain data, start with a free block explorer: mempool.space for Bitcoin and Etherscan for Ethereum let anyone look up a transaction, an address or a block without an account. This guide explains each step and what network metrics reveal.
How to read on-chain data: what a block explorer shows
A block explorer is a website that reads data from blockchain nodes and displays it in a searchable form. For Bitcoin, this guide uses mempool.space, an open-source explorer. For Ethereum, it uses Etherscan. Both offer a single search box that accepts three kinds of input:
- A transaction ID (also called a txid or transaction hash): a long string of letters and numbers that works like a receipt number.
- An address: the public identifier that receives and sends coins.
- A block, by its height (its number in the chain) or its hash.
The mempool.space FAQ describes exactly this: the search box at the top of the page looks up a transaction by ID, an address, or a block by height or hash. Etherscan works the same way.
Before you start, one safety rule. Reading a blockchain never requires your seed phrase, private key or wallet connection. An explorer that asks for any of these is not an explorer you should use.
Bitcoin vs Ethereum: the basics side by side
The two largest networks record data differently, so explorer pages look different. The table below summarises the protocol facts that matter for reading them.
| Feature | Bitcoin | Ethereum |
|---|---|---|
| Accounting model | Unspent transaction outputs (UTXOs); a balance is the sum of UTXOs a wallet controls | Accounts with balances; each transaction moves value or calls contract code |
| Block timing | Difficulty resets every 2,016 blocks against a two-week target (1,209,600 seconds), which implies about 10 minutes per block | Time is split into 12-second slots; 32 slots make one epoch |
| Fee unit | Satoshis per virtual byte (sat/vB) | Gas, priced in gwei (1 gwei = 0.000000001 ETH) |
| Simple transfer cost | Depends on transaction size in bytes and the fee rate chosen | 21,000 gas multiplied by (base fee + priority fee) |
| Where the fee goes | To the miner who finds the block | Base fee is burned; the priority fee (tip) goes to the validator |
| Common explorer | mempool.space | Etherscan |
Sources: Bitcoin developer guide (transactions and block chain sections); ethereum.org (transactions and proof-of-stake pages); Etherscan Information Center (gas fees).
Step 1: Look up a Bitcoin transaction on mempool.space
Paste a transaction ID into the search box. If you do not have one, open any recent block from the homepage and click a transaction inside it. The page you land on has three parts worth reading.
Status: unconfirmed or confirmed
A transaction is "unconfirmed" while it waits in the mempool, which mempool.space defines as the queue of pending, unconfirmed transactions held by a network node. Once a miner includes it in a block, the page shows it as confirmed and counts how many blocks have been added since. Each new block makes older blocks more expensive to rewrite, because every block stores the hash of the one before it. Exchanges and services set their own rules on how many confirmations they wait for, so check the service you use.
Inputs and outputs
The left side lists inputs and the right side lists outputs. According to the Bitcoin developer guide, each input spends an output from an earlier transaction, identified by that transaction's ID and the output's position. Each output pays an amount to a script, usually shown as an address.
A common beginner mistake is to read every output as a payment. Often one output is the payment and another is change: because the full value of an input must be spent, the leftover returns to the sender, usually at a fresh address. An explorer cannot always tell you which output is which.
Fee and fee rate
Bitcoin has no explicit fee field. The fee is the total value of the inputs minus the total value of the outputs, and it goes to the miner. Explorers show it both as a total and as a rate in sat/vB. Miners tend to choose higher-paying transactions first, so the rate, not the total, decides how quickly a transaction confirms.
The mempool.space homepage shows suggested rates labelled High, Medium and Low priority. Its FAQ explains that these are based on the median fee rates of the next projected blocks, and warns that they do not guarantee confirmation in any timeframe. If a transaction is stuck, the FAQ describes two fixes: Replace-By-Fee (RBF), if the original was sent with RBF enabled, and Child-Pays-For-Parent (CPFP), where you spend one of its outputs with a high fee to pull the parent through.
Step 2: Look up a Bitcoin address
Search for an address and the explorer lists every transaction that touched it, with the total received, total sent and current balance. Two cautions apply.
- One person, many addresses. Wallets routinely use new addresses for change, so one person's funds are often spread across many addresses. A single address rarely shows someone's full holdings.
- Labels are guesses. When an explorer or analytics firm tags an address as belonging to an exchange or a company, that label comes from public disclosures, tags or clustering methods. It is not written on the blockchain itself.
Addresses are pseudonymous, not anonymous. If you publish your own address next to your name, anyone can follow its history.
Step 3: Read an Ethereum transaction on Etherscan
Paste a transaction hash into Etherscan, or pick one from the "Latest Transactions" list on its homepage. The details page maps closely onto the fields that ethereum.org lists for every transaction:
- Status: Etherscan's help pages say a completed transaction reads "Success". Pending and failed transactions are labelled separately.
- From: the sending account, which signed the transaction. Only externally owned accounts (normal wallets) can start transactions.
- To: the recipient. If it is a wallet, ETH moves. If it is a contract, the transaction runs that contract's code.
- Value: the ETH sent. Internally it is counted in wei, where 1 ETH equals 1018 wei.
- Nonce: a counter of how many transactions the sending account has made. It explains why transactions from one wallet confirm in order.
- Gas limit and usage, gas price, burnt fees: the fee breakdown, explained below.
- Input data: optional data, used mainly when calling a contract.
How the Ethereum fee is calculated
Since the EIP-1559 change, each unit of gas costs a base fee, set by the network and burned, plus an optional priority fee (tip) that goes to the validator. Users also set a maximum fee per gas, and unused gas is refunded.
ethereum.org gives a worked example for a simple 21,000-gas transfer. With a base fee of 190 gwei and a tip of 10 gwei, the total is (190 + 10) × 21,000 = 4,200,000 gwei, or 0.0042 ETH. Of that, 0.00399 ETH is burned and 0.00021 ETH goes to the validator. Real fees are usually far lower or higher than this illustration, depending on demand at the time.
Finality
ethereum.org explains that a block included in the chain is later "justified" and then "finalized". Changing a finalized block would require an attack that the page says would cost many billions of dollars. Etherscan shows how many blocks have been added after a transaction, which helps you see how settled it is.
Step 4: Find a token transfer and internal transactions
Here is where many beginners get confused. When you send a token such as a stablecoin, you do not send it to the recipient directly. Your wallet calls the token's smart contract, which updates its own ledger. On the details page, that means:
- The To field shows the token contract, not your friend's wallet.
- The Value field often shows 0 ETH, because no ether moved.
- The real movement appears in a separate section listing the tokens transferred, with sender, recipient, amount and token name.
On an address page, Etherscan splits activity into tabs: normal transactions, internal transactions and token transfers. Internal transactions are value movements that a contract makes while it runs, for example when a contract pays out ETH. MetaMask's help centre notes that wallets may not display them because they happen during code execution, while explorers such as Etherscan track them. If funds seem to be "missing" from a wallet's history, the internal or token tabs are the first place to check.
One more warning: scammers create tokens with names that copy well-known projects. Always check the contract address of a token, not just its name or logo.
Step 5: Understand the common on-chain metrics
Charts built from on-chain data appear constantly in crypto coverage, including in our market reports. Each metric below is useful, but each also has limits that are easy to miss.
| Metric | What it measures | What it does not tell you |
|---|---|---|
| Active addresses | Unique addresses that sent or received in a ledger change during a period, each counted once (Coin Metrics definition) | The number of people. One person can use many addresses, and Coin Metrics warns the figure can be "trivially forged" on chains where transactions are cheap |
| Exchange inflows and outflows | Coins moving to and from addresses labelled as exchange wallets (Glassnode) | Intent. Exchanges move funds internally and change addresses, and Glassnode says its exchange balances are lower bounds that can be revised |
| Fees and fee rates | Demand for block space at a given time | Who is paying or why. A single busy application can push fees up |
| Hash rate (Bitcoin) | An estimate of total mining computing power, derived from difficulty and recent block times; Bitcoin Core's estimate uses the last 120 blocks by default | An exact measurement. It cannot be observed directly, and short windows are noisy because block discovery is random |
Sources: Coin Metrics documentation (AdrActCnt); Glassnode Exchange Data Transparency Notice; Bitcoin Core RPC reference (getnetworkhashps); mempool.space FAQ.
Active addresses
Coin Metrics counts an address as active if it sent or received in any ledger change during the period, and counts it only once even if it was active many times. Zero-value and failed transactions still count. That makes the metric a rough gauge of how busy a network is, not a user count. Comparing chains is tricky too, because Coin Metrics notes the figure inherits quirks from each chain's design.
Exchange flows
Exchange flow data depends entirely on which addresses an analytics firm believes belong to exchanges. Glassnode's transparency notice explains that its labels combine exchange disclosures, public tags and clustering algorithms, and that complete accuracy is not achievable. It also cautions that large flows can be misleading when exchanges reshuffle their own wallets. Treat a sudden spike as a question to investigate, not as a conclusion.
Fees
Fee levels show how much users are competing for block space. On mempool.space you can watch projected blocks fill up; on Etherscan the gas tracker shows current gas prices. High fees mean high demand at that moment, whether from payments, token launches or automated activity.
Hash rate
Bitcoin's hash rate is the estimated number of hashes per second miners are performing. The Bitcoin Core software describes its own figure as an estimate "based on the last n blocks". Because blocks arrive at random intervals, a few lucky or unlucky hours can make the estimate jump without any real change in mining. The difficulty adjustment every 2,016 blocks is what keeps block times near their target as mining power changes.
What it means
Block explorers turn a blockchain into something anyone can audit. With a few searches you can confirm whether a payment arrived, see what fee it paid, follow a token transfer through a contract and spot why a transaction is stuck. That is valuable for everyday users, for journalists checking claims, and for anyone following network upgrades such as the Zcash NU7 upgrade or Solana's Alpenglow.
The limits matter as much as the tools. Addresses are not people, labels are estimates, and metrics such as exchange flows and hash rate are modelled, not measured. On-chain data describes what happened on a network; it does not explain motives and it does not forecast prices. Readers interested in how blockchains are entering traditional finance can also read our explainers on tokenized stocks and the OCC's GENIUS Act stablecoin rule.
Frequently asked questions
Is it safe to look up a wallet address on a block explorer?
Yes. Block explorers only read public blockchain data, so looking up an address or transaction does not require a seed phrase, private key or wallet connection. Never enter those on any explorer. Remember that addresses are pseudonymous: if you link your own address to your name publicly, anyone can follow its history.
Why does my Ethereum token transfer show 0 ETH on Etherscan?
Tokens move when your wallet calls the token's smart contract, so the transaction's To field shows the contract and the Value field often shows 0 ETH. The actual token movement is listed separately as a token transfer, and on an address page it appears in the token transfers tab.
Why is my Bitcoin transaction still unconfirmed?
Miners tend to pick transactions with higher fee rates, measured in sat/vB, so a low-fee transaction can wait in the mempool for a long time. According to mempool.space, it can be sped up with Replace-By-Fee if it was sent with RBF enabled, or with Child-Pays-For-Parent by spending one of its outputs with a higher fee.
Do active addresses show how many people use a blockchain?
No. Active addresses count unique addresses that sent or received during a period. One person can control many addresses, and Coin Metrics notes the figure can be easily inflated on chains where transactions are cheap, so it is a rough gauge of activity rather than a user count.
Sources
- mempool.space: FAQ
- Bitcoin Developer Guide: Transactions
- Bitcoin Developer Guide: Block Chain
- Bitcoin Core RPC reference: getnetworkhashps
- ethereum.org: Transactions
- ethereum.org: Proof-of-stake
- Etherscan Information Center: What is Gas Fee?
- Etherscan Information Center: Understanding an Ethereum Transaction
- MetaMask Support: Internal transactions
- Coin Metrics: Active Addresses (AdrActCnt)
- Glassnode: Exchange Data Transparency Notice
This article is for information only and is not investment advice.
