Empty Block Mining: Definition and Why Some Bitcoin Blocks Contain No Transactions
Empty Block Mining is the practice of mining a Bitcoin block that contains only the coinbase transaction and no regular user transactions. Although technically valid, empty blocks are relatively uncommon and are usually mined to reduce the delay between discovering one block and beginning work on the next.
Empty Block Mining Explained in Simple Terms
When a new Bitcoin block is found, miners want to begin mining the next block as quickly as possible.
Building a complete candidate block requires:
receiving the latest transactions
selecting which transactions to include
calculating a new Merkle root
These steps take a small amount of time.
To avoid sitting idle, some miners immediately start mining a simple block containing only the coinbase transaction.
This is known as empty block mining.
Later, once the full list of transactions is available, miners typically switch to a normal block template containing user transactions.
Think of it like a race where runners begin moving as soon as the starting signal sounds instead of waiting to organize all their equipment first. Starting immediately can sometimes outweigh the small benefit of extra preparation.
How Empty Block Mining Works
Empty block mining occurs immediately after a new block is discovered.
The process works as follows:
New Block Found
The miner receives the latest accepted Bitcoin block.Mining Starts Immediately
Instead of waiting to assemble a full block, the miner creates a minimal candidate block.Coinbase Transaction Added
Only the mandatory coinbase transaction is included.Proof of Work Begins
Mining starts without waiting for additional transactions.Template Updated
Once a complete block template is ready, the miner usually switches to mining the full version.
The process can be summarized as:
New Block → Minimal Candidate Block → Immediate Mining → Full Template Update
Example of Empty Block Mining in Practice
A mining pool receives notification that another pool has successfully mined a new Bitcoin block.
To minimize downtime, it immediately begins mining the next block using:
the previous block hash
a coinbase transaction
no regular transactions
A few seconds later, after rebuilding the mempool and selecting high-fee transactions, the pool generates a full block template and switches miners to the updated version.
If the empty block happened to be mined before the update, it would still be a completely valid Bitcoin block.
Why Empty Block Mining Happens
Empty block mining is mainly an optimization technique.
It helps miners:
reduce idle mining time
begin hashing immediately after a new block
maximize their chance of finding the next block
avoid delays while assembling a new candidate block
The strategy is based on the idea that every second of hashing contributes to the probability of earning the next block reward.
Why Don't Miners Always Mine Empty Blocks?
Although empty blocks are faster to prepare, they have a significant disadvantage.
They contain:
no regular transactions
little or no transaction fee revenue
A full block usually earns:
the block subsidy
plus all transaction fees from included transactions
As transaction fees become a larger portion of miner revenue, mining full blocks becomes increasingly attractive.
For this reason, most miners switch to a complete block template as soon as possible.
Empty Block Mining vs Normal Block Mining
Empty Block Mining
Contains:
only the coinbase transaction.
Advantages:
fastest possible start
minimal preparation time
Disadvantages:
little or no transaction fee income
Normal Block Mining
Contains:
the coinbase transaction
regular Bitcoin transactions
Advantages:
higher total rewards
confirms pending transactions
Disadvantages:
requires more time to assemble the candidate block
Does Empty Block Mining Harm the Network?
Occasional empty blocks are considered normal and do not threaten Bitcoin's security.
However, if miners consistently produced empty blocks:
transaction confirmations would slow down
the mempool would grow
transaction fees could increase because fewer transactions would be confirmed
In practice, empty blocks represent only a small percentage of all mined blocks, and most miners prefer collecting transaction fees whenever possible.
Can an Empty Block Still Earn the Block Reward?
Yes.
An empty block is fully valid as long as it satisfies Bitcoin's consensus rules and includes the required coinbase transaction.
The miner receives:
the block subsidy
any transaction fees included in the block
Since an empty block contains no regular transactions, the fee portion is typically zero or negligible.