A <a href="/en/glossary/blockchain-fundamentals/block/">Block</a> explorer is a website tool for querying all public records on a blockchain — like a search engine for the chain. You can use it to look up the details of any transaction, the balance and history of any wallet address, the status of any <a href="/en/glossary/blockchain-fundamentals/smart-contract/">Smart Contract</a>, and the information of every block on the chain. Because blockchain data is public and transparent, anyone can query this without an account or permission. It's the transparent ledger of the on-chain world and the most direct tool for verifying whether a transfer arrived or whether an address looks suspicious.

An on-chain analysis method that tracks <a href="https://claude-me.com/en/glossary/core-concepts/token/">Token</a> movement between regular addresses (cold wallets, investor accounts) and exchange addresses. Tokens flowing into exchanges are typically interpreted as selling intent (you need to send coins to an exchange to sell them); tokens flowing out of exchanges represent a holding or self-custody tendency (withdrawing coins from an exchange signals no immediate plan to sell). It's one of the key on-chain indicators for reading market supply pressure.

A trader sees another's pending (unconfirmed) transaction and submits their own before it's confirmed. Example: User wants to buy 1,000 tokens for $1. A bot sees the pending transaction, submits 'buy 10,000 tokens for $1' with higher <a href="/en/glossary/onchain-data/gas-fee/">Gas Fee</a>, executes first. Bot gets cheap tokens; user's transaction executes after at higher price. Bot profits. <a href="/en/glossary/onchain-data/front-running/" target="_blank">Front-Running</a> is blockchain's most common unfair trading practice.

The fee you pay the network for any on-chain action (transfers, trades, contract interactions) to cover the cost of computation and validation. It's usually paid in the chain's native <a href="https://claude-me.com/en/glossary/core-concepts/token/">Token</a> (for example, ETH on Ethereum), and its level floats with network congestion — the more people competing to get on-chain at once, the higher the <a href="/en/glossary/onchain-data/gas-fee/" target="_blank">Gas Fee</a>.

The mempool (memory pool) is the waiting area where blockchain nodes temporarily hold transactions that have been broadcast but not yet packed into a <a href="/en/glossary/blockchain-fundamentals/block/">Block</a>. After you send a transaction, it doesn't go on-chain instantly but first queues in each <a href="/en/glossary/blockchain-fundamentals/node/">Node</a>'s mempool, waiting to be picked and packed into the next block by a miner or validator. Because the mempool is publicly visible — who paid a higher fee, who might get prioritized — this is also why phenomena like fee-bumping to jump the queue, MEV, and <a href="/en/glossary/onchain-data/front-running/">Front-Running</a> occur.

MEV (Maximum Extractable Value) is the profit validators (or miners) can extract above ordinary <a href="/en/glossary/blockchain-fundamentals/block/">Block</a> rewards and fees by selecting, reordering, inserting, or deleting transactions when packing a block. In simple terms, from the moment you send a transaction to when it's packed into a block, anyone who can see it (miners, MEV bots) has an information advantage — they can execute specific operations before or after you and capture the profit that would otherwise have been yours.

On-chain analytics is the systematic analysis of publicly accessible transaction data on blockchains to infer market participant behavior, position distribution, capital flows, and overall market sentiment cycles. Because of blockchain's transparency, every transfer and every position change is permanently recorded; the essence of on-chain analysis is converting this raw data into meaningful market insights. Common on-chain indicators include exchange inflow/outflow volumes, <a href="/en/glossary/onchain-data/whale/">Whale</a> address position changes, and MVRV ratio (market cap vs. realized cap).

<a href="/en/glossary/depegging-risk/proof-of-reserves/" target="_blank">Proof of Reserves (PoR)</a> is a transparency mechanism used by cryptocurrency exchanges or custody institutions to prove to users and the public that they genuinely hold the corresponding reserves for all user assets. FTX's collapse (November 2022) revealed the enormous risks of exchanges misappropriating user assets, driving industry-wide adoption of <a href="https://stablecoin-bible.com/en/glossary/depegging-risk/reserve-proof-of-reserves/">Proof of Reserves</a>. Technically, PoR typically combines a <a href="/en/glossary/blockchain-fundamentals/merkle-tree/">Merkle Tree</a> with verifiable on-chain addresses: placing all user account balances into a Merkle tree, allowing any user to verify their balance is included in the total reserves, while the exchange's on-chain addresses' holdings can be independently verified.

Realized cap is one of the most important valuation foundations in Bitcoin on-chain analysis, calculated by valuing each bitcoin (or each on-chain trackable UTXO) at the market price at the time it last moved, then summing them up. It approximates the average cost basis of all holders. Unlike market cap which fluctuates wildly with price, realized cap moves relatively smoothly, closer to the market's true capital input. MVRV (market cap ÷ realized cap) is the most commonly used on-chain valuation signal derived from it.

<a href="/en/glossary/onchain-data/sopr/" target="_blank">SOPR (Spent Output Profit Ratio)</a> is one of the most important sentiment indicators in Bitcoin on-chain analysis, developed by Renato Shirakashi in 2019. Calculation: for all Bitcoin UTXOs that moved on a given day, divide the market price at this move by the market price at the last move, then average them. SOPR > 1 means the market overall is selling at a profit (sellers' average sell price above their average entry cost); SOPR < 1 means the market is overall selling at a loss (panic capitulation). SOPR is a real-time P&L snapshot of market sentiment, showing whether people moving capital now are exiting profitably or capitulating.

In crypto markets, a <a href="/en/glossary/onchain-data/whale/" target="_blank">Whale</a> refers to an individual wallet address or institutional entity holding such a large amount of crypto assets that their trading behavior can produce observable effects on market prices. There's no precise threshold definition, but addresses holding over 1,000 BTC or equivalent are typically considered Bitcoin whales; for smaller-cap tokens, addresses holding over 1% of total supply may be considered whales. On-chain data analysts track whale capital flows — especially whether large amounts of tokens are transferred to exchanges (potential selling) or withdrawn from exchanges to cold wallets (potential accumulation) — to infer large-capital market direction.