On April 21, 2026, the Bitcoin Core development team officially released version 31.0, bringing the most significant transaction processing architecture change since Bitcoin's inception. This upgrade centers on "Cluster Mempool" and introduces Tor/I2P privacy broadcasting capabilities, marking a major breakthrough in Bitcoin network performance and privacy protection.
Why This Upgrade Matters
Bitcoin's mempool (memory pool) is the staging area for unconfirmed transactions, from which miners select transactions to include in blocks. The previous architecture was inefficient when handling complex transaction dependencies, leading to:
- Suboptimal block template construction
- Inaccurate fee estimation
- RBF (Replace-By-Fee) decisions that could harm overall network welfare
Version 31.0's Cluster Mempool fundamentally redesigns this system.
Cluster Mempool: A Revolutionary Architecture Change
Core Concept
Tip
Cluster Definition: Transactions connected through any combination of parent/child relationships are considered part of the same cluster.
The new architecture introduces two key limits:
- Maximum 64 transactions per cluster
- Maximum 101 kB per cluster
This replaces the previous ancestor/descendant count limits, allowing nodes to more precisely evaluate the economic value of transaction groups.
Three Core Improvements
1. Smarter Block Template Construction
Transactions are now ordered based on the feerate at which they are expected to be mined. When miners construct blocks, algorithms can more accurately select the most profitable transaction combinations, avoiding missed high-value transactions or inclusion of low-value ones.
Old architecture: Per-transaction evaluation, may miss global optimum
New architecture: Cluster-based evaluation, selects feerate-diagram-optimal combinations
2. Improved RBF Validation Logic
Warning
Major Change: Transaction replacements are now only accepted if "the resulting mempool's feerate diagram is strictly better than before the replacement."
This eliminates all known cases where replacements made the mempool worse off, which was possible under previous RBF rules and harmed overall network welfare.
3. Efficient Memory Management
When the mempool is full, the system can now more precisely decide which transactions to evict. Feerate-based ordering ensures low-value transactions are removed first while high-value transactions are retained.
New RPC Commands
Developers and advanced users can utilize two new RPC commands:
| Command | Function |
|---|---|
getmempoolcluster | Query cluster information for a specific transaction |
getmempoolfeeratediagram | Get the feerate distribution diagram of the mempool |
Tor/I2P Privacy Broadcasting: Protecting Your Identity
The Problem
When you send a Bitcoin transaction, your IP address is exposed to the nodes that first receive it. Observers can analyze transaction propagation patterns to track the sender's geographic location and even correlate multiple transactions from the same person.
The Solution: -privatebroadcast
The new -privatebroadcast option in v31.0 provides revolutionary privacy protection:
Tip
When enabled, transactions are broadcast exclusively through Tor or I2P networks, providing two layers of protection:
- IP Hiding: Receiving nodes never know the sender's real IP
- Transaction Isolation: Each transaction uses a separate connection, preventing correlation
New RPC Commands
| Command | Function |
|---|---|
getprivatebroadcastinfo | Query transactions currently being privately broadcast |
abortprivatebroadcast | Remove specified transactions from the private broadcast queue |
Usage Recommendations
Warning
Privacy broadcasting increases transaction propagation latency. If you need fast confirmations and aren't concerned about privacy, you may not need to enable this feature.
When to enable:
- Sending large transactions
- Users with high privacy requirements
- Operating in potentially monitored network environments
Other Important Updates
Performance Improvements
| Item | Old Value | New Value |
|---|---|---|
| Default database cache | 450 MiB | 1024 MiB |
| Minimum fee estimator bucket | 1 sat/vB | 0.1 sat/vB |
Tip
The doubled database cache means significantly faster Initial Block Download (IBD) speeds—great news for new node operators.
Embedded ASMap Data
For the first time, AS (Autonomous System) mapping data is embedded, allowing the ASMap feature to work without external files. This helps improve node peer connection diversity, enhancing network decentralization.
GUI Upgrade
The graphical interface has been upgraded to Qt 6.8, bringing a more modern user experience.
Removed Features
Danger
The following options have been removed—verify your configuration before upgrading:
-paytxfeeandsettxfee(deprecated options)-maxorphantxoption- CPFP carveout feature
Impact on Different Users
Regular Bitcoin Users
- More accurate fee estimation: Wallets can more precisely suggest appropriate fees
- Faster confirmation times: Fee competition becomes fairer during congestion
- Optional privacy enhancement: Enable privacy broadcasting when needed
Node Operators
- More efficient memory usage: Cluster limits prevent memory explosion
- Faster sync speeds: Doubled cache accelerates initial synchronization
- Better peer connections: Embedded ASMap improves network topology
Miners
- Maximized block revenue: Smarter block templates select the most profitable transactions
- More stable fee income: Improved RBF logic prevents low-fee replacement attacks
Developers
- New RPC commands: More mempool state query tools
- More predictable transaction behavior: Cluster limits make transaction dependencies clearer
How to Upgrade
Node Operators
- Backup your
wallet.datandbitcoin.conf - Download v31.0 from bitcoincore.org
- Verify the SHA256 hash of the download
- Stop your existing node and replace the executable
- Start the new version and monitor logs for normal operation
Warning
v31.0 requires higher compiler versions (Clang 17.0+, GCC 12.1+)—users compiling from source take note.
Regular Users
If your wallet (such as Sparrow or Electrum) connects to your own node, upgrading the node will automatically benefit from new features. If using third-party nodes, you'll need to wait for service providers to upgrade.
Looking Forward
Bitcoin Core v31.0 is an important milestone in Bitcoin protocol evolution. The Cluster Mempool architecture lays the foundation for future improvements, including:
- More refined RBF policies: Feerate-diagram-based decision logic is extensible
- Layer 2 integration optimization: Lightning Network and other second-layer protocols will benefit from more predictable on-chain behavior
- Further privacy enhancements: Privacy broadcasting is just the first step
Tip
Bitcoin Core development follows conservative principles. Each upgrade undergoes rigorous testing—v31.0rc4 ran on testnet for weeks before the official release to ensure stability.
Conclusion
Bitcoin Core v31.0 represents years of effort from the Bitcoin Core development team. Cluster Mempool redefines transaction processing logic, while the privacy broadcasting feature responds to the community's long-standing demand for privacy protection.
Whether you're a node operator, miner, developer, or regular user, this upgrade deserves attention. It not only improves network performance but also builds a more solid foundation for Bitcoin's long-term development.
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