Censorship Resistance
How the alt mempool and Shared Mempool protect UserOp inclusion.
From the very beginning, ERC-4337 was designed to support a decentralized, censorship-resistant transaction flow for Account Abstraction. A key part of that vision was the creation of a separate, peer-to-peer mempool for UserOperations, distinct from Ethereum’s native transaction mempool. However, realizing this architecture took time — and until late 2024, most bundlers relied on private, isolated queues that undermined the original goals.
⚠️ Centralization Risk Without Global Propagation
In a fragmented ecosystem:
Bundlers can selectively drop or ignore
UserOperationsUsers relying on a single RPC or bundler can be censored
Unlike Ethereum’s canonical mempool, inclusion guarantees are weaker unless the network shares UserOps widely.
🌐 Shared Mempool: Live and Decentralized
As of November 2024, the ERC-4337 Shared Mempool is live on Ethereum, Arbitrum, and Optimism. This milestone was achieved through a multi-team collaboration involving Etherspot, Candide, Alchemy, and others, marking a transition from private relays to a decentralized propagation layer for UserOps:
Bundlers publish metadata to IPFS
Peers use this metadata to discover compatible UserOps
Valid operations propagate across nodes via gossip
Rather than requiring users to target a specific bundler, the shared mempool enables any participating bundler to see and process a submitted UserOperation — mimicking the visibility guarantees of Ethereum’s base-layer mempool.
This makes censorship significantly harder. A malicious or non-cooperative bundler can no longer act as a gatekeeper: other bundlers will still see the UserOp and can include it in a valid bundle.
💡 Design Implications for Developers
Always integrate multiple bundler endpoints
Prefer relayers that participate in the Shared Mempool
Monitor submission status and resubmit if needed
🌿 From Training Wheels to Full Decentralization
The rollout of the shared mempool follows a staged maturity framework, inspired by Vitalik’s rollup decentralization stages:
Stage 0: Private Queues — No mempool, just per-bundler UserOp handling
Stage 1: Permissioned Sharing — Only whitelisted bundlers propagate UserOps
Stage 2: Controlled Decentralization — Shared but semi-restricted propagation
Stage 3: Fully Permissionless — Any compliant bundler can join and relay
The ecosystem is currently transitioning from Stage 1 to Stage 2, with growing adoption of peer-to-peer relays and emerging tooling to inspect and verify bundler behavior.
🤝 Relevance to EIP-7702
Even outside of ERC-4337, the Shared Mempool helps:
EIP-7702 introduces temporarily smart-enabled EOAs
These can be relayed via the UserOp mempool, not the canonical one
This enhances censorship resistance for wallets adopting 7702 logic
Ethereum.org recommends using the UserOp mempool as a best practice for 7702 onboarding:
“Consider using the UserOperation mempool for relaying smart EOA transactions to avoid base-layer censorship.”
📖 Learn more:
⭐️ Why This Matters
Without a shared propagation layer, censorship resistance is impossible. The ERC-4337 shared mempool finally delivers on the standard’s decentralization promise — improving inclusion guarantees, reducing single bundler risk, and making it easier for wallets to route UserOps through resilient pathways.
Even with this infrastructure in place, users must still choose bundler-connected RPCs that support the mempool. Ecosystem adoption is growing fast, and continued tooling will make it easier to monitor bundler behavior and performance in this new permissionless layer.
✅ Summary
Censorship resistance in Account Abstraction depends on open submission infrastructure. The live Shared Mempool, now standard in the ERC-4337 ecosystem, ensures that UserOperations can’t be easily suppressed or filtered, and even benefits 7702 workflows.
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