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Learning objectives

  • Read and interpret block and chain data using Bitcoin Core commands
  • Understand chain tips and how re-orgs occur in regtest
  • Track transaction confirmations and understand depth
  • Inspect the mempool for unconfirmed transactions

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Reading block data

After mining blocks in regtest or syncing a mainnet/testnet node, you can inspect block data using several bitcoin-cli commands. Get the hash of the most recent block:
Retrieve full block data using the hash:
To get just the header:
This includes:
  • Height
  • Timestamp
  • Version
  • Merkle root
  • Previous block hash
  • Nonce
  • Chainwork
Get block hash by height:
Example:

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Using getchaintips and understanding chain re-orgs

The command getchaintips returns all known tips of the blockchain:
This is useful in regtest when you’re simulating chain reorganizations. For example, if you invalidate a block:
Then generate a longer competing chain (replace <miner_address> with your mining address):
Your node will adopt the longer chain tip, causing a re-org. This is how Bitcoin resolves consensus forks.

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Understanding confirmations and depth

A transaction’s confirmation count is the block that includes it plus every block on top of that block. To see how many confirmations a transaction has (replace <txid> with an actual transaction ID):
You’ll see:
  • confirmations: number of blocks since inclusion, counting the block it was mined in
  • blockhash: which block it was mined in
Alternatively, use :
To simulate confirmations in regtest, simply mine more blocks (replace <miner_address> with your mining address):
This simulates time passing and increases confirmation depth instantly.

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Inspecting mempool transactions

The mempool holds transactions waiting to be mined. In regtest, it’s typically empty unless you send a transaction before mining. List all mempool transactions:
Get details of a specific mempool transaction (replace <txid> with an actual transaction ID):
This shows:
  • Fee
  • Size
  • Ancestor/descendant count
  • Time in pool
You can clear the mempool by mining a block that confirms the pending transactions, or by restarting the node with -persistmempool=0. A plain restart keeps it, because the node saves the mempool to mempool.dat.

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Activity

  1. Generate five blocks and get the latest block hash
  2. Use getblock and getblockheader to inspect the block
  3. Send a transaction and observe it in the mempool before mining.
  4. Mine one block and check the transaction’s confirmation count.
  5. Invalidate the block using invalidateblock , then, inspect with getchaintips