Think of a transaction block as a digital container or folder. It holds a group of transactions (things like payments, smart contract actions, or data updates) all bundled together and recorded on a blockchain.
Most blockchains, including Avalanche, organize their data this way. But how those blocks get created and validated depends on the type of consensus mechanism being used. Let’s break down the two big ones:
Proof-of-Stake (PoS) In PoS systems like Avalanche, validators (also called stakers) create transaction blocks. They’re selected based on how much cryptocurrency they’ve locked up as collateral—plus a few other factors like randomness or reputation.
A PoS transaction block usually includes:
✅ Transactions: things like sending tokens, running smart contracts, or updating data
📦 Block Header: this stores:
Block height: its place in the chain
Timestamp: when the block was created
Previous block’s hash: a digital link to the last block
Merkle root: a special fingerprint of all the transactions in the block, making it tamper-proof
Wait, what’s a Merkle root? Think of it as a single summary code for all the transactions in the block. If even one letter in a transaction changes, the Merkle root changes too, so it’s super easy to tell if data was tampered with.
🔏 Validator signature: a digital seal that proves who created the block
📊 Staking info: details on how much crypto the validator locked up to be eligible (his collateral)
🧩 Consensus mechanism: the rulebook everyone follows to agree on what’s valid. It ensures the block is accurate and agreed upon.
🎁 Rewards: validators get rewards (like transaction fees or tokens) for doing their job honestly
PoS also has fast finality, meaning once a block is added, it’s locked in and very unlikely to change.
Proof-of-Work (PoW) In PoW blockchains like Bitcoin, miners compete to create the next block by solving a complex math puzzle. This takes serious computing power, and is part of what keeps the network secure.
A PoW transaction block includes:
✅ Transactions: bundled to improve network efficiency
🧩 Block header: includes:
Nonce: a random number that miners keep changing until the puzzle is solved
What's a nonce? It’s like a guess. Miners keep guessing random numbers (the nonce) to find a block hash that meets the network’s criteria—kind of like cracking a safe by guessing the combo. First to succeed wins the block.
Merkle root: just like in PoS, it ensures data integrity
Previous block hash and timestamp
🧩 Proof-of-work: a mathematical proof showing the miner did the work
⚙️ Difficulty target: adjusts automatically to make sure blocks aren’t created too fast or too slow
💰 Mining rewards: miners earn crypto (like Bitcoin) if they find a valid solution. It's what incentivizes miners to keep the network running.
PoW takes more energy and time.
No matter the method, transaction blocks are the building blocks (literally) of blockchain networks. Transaction blocks are what make the blockchain a chain. Each one links to the last, forming a secure, chronological, tamper-resistant record. They make the system work: securely, transparently, and without relying on centralized control.