Block explorer basics

What you are looking at

Three pages matter for whale-watching:

• Transaction — /tx/{txid}. Inputs (spent previous outputs), outputs (new UTXOs), fee, virtual size, RBF signaling, confirmation status.
• Block — /block/{hash} or height. The full list of transactions that were included together. This is what our Radar scans.
• Address — /address/{addr}. A convenience sum of UTXOs locked to that script. It is not an account.

If a number on this site disagrees with the explorer, trust the explorer (or your own node) and tell us.

Reading a transaction page

Work top to bottom:

1. Status. Confirmed shows a block height and a timestamp. Unconfirmed sits in a mempool view and can still be replaced or dropped. See mempool vs confirmed.
2. Fee and fee rate. Fee is inputs minus outputs (or the explicit fee field). Rate is satoshis per virtual byte. Priority is rate, not BTC size.
3. Vin / vout counts. Count them before you read any “whale” caption. Many→one is a consolidation candidate; one→many is a batch candidate; 1→2 is often payment plus change.
4. Values. Output amounts are in BTC or sats. The sum of outputs is what Radar uses as “BTC moved.” That sum includes change.
5. Addresses. Copy one and search our label directory. No match is the normal case.

Worked path (sourced tx)

Open this Bitfinex consolidation on mempool.space ↗ (block 615825). You should see 147 inputs, 1 output, a fee on the order of 0.005 BTC, and a confirmed status. Then paste the same txid into Brief. The Brief’s first logic steps should match those counts. The label on an input is a directory hit, not a guess by the explorer. Narrative context lives on Examples — keep it separate from the raw fields.

RBF, CPFP, and why the txid can change

If the transaction signals replace-by-fee, a higher-fee version can appear with a new txid that spends the same inputs. The old pending hash becomes a ghost. Child-pays-for-parent is different: a later transaction pays a high fee to pull an underpaid parent into a block; both txids remain. Neither mechanism is a price signal. They are mempool policy. Radar lists only confirmed transactions, so a txid you copy from it should still resolve the next day.

Address pages: the trap

An address page shows received, sent, and a current sum of unspent outputs. It does not show “this person.” Many entities use new addresses per payment. Some reuse hot-wallet addresses for years. Tribute payments to famous scripts (genesis, hack addresses) inflate “received” without implying the original actor is active. Our labels are exact-match and sourced; explorer tags from other sites may be crowdsourced and unsigned. Prefer a primary link.

API vs UI

The same host exposes JSON: /api/tx/{txid}, /api/blocks, /api/v1/block/{hash}/summary. Radar uses the block summary so it can filter every transaction in recent blocks — not the ~10-tx /api/mempool/recent sample. You can call those endpoints yourself. We do not operate a mirror and we do not guarantee uptime. Details: Methodology.

Weight, vsize, and why sat/vB exists

Bitcoin measures transaction size in weight units (segwit). Explorers usually show virtual size (weight ÷ 4) and a fee rate in satoshis per virtual byte. A large BTC amount can sit in a small transaction (few inputs). A modest amount can sit in a huge transaction (hundreds of inputs). That is why Radar’s sat/vB column is not a “importance” score — it is inclusion priority. The Developer Guide’s transaction chapter is the reference for “an output is spent in full.”

Coinbase transactions are not whale transfers

The first transaction in a block is the coinbase: newly issued subsidy plus fees, with no previous inputs in the usual sense. It can be thousands of BTC. It is minting plus miner payout, not “a whale sent coins.” Radar’s block-summary filter still sees output sums; if a coinbase output total cleared a threshold it could appear. Read the explorer’s “coinbase” mark before treating that row as a transfer. See the Developer Guide on the block chain.

A short explorer checklist

1. Confirmed or not?
2. Input count, output count, output sum, fee rate.
3. Any exact label in our directory?
4. Does Brief’s logic list match the explorer fields?
5. Only then read a narrative — or refuse one.

Next: reading large transactions and the Radar.

Disclaimer.