Dencun is the Ethereum network upgrade that went live on March 13, 2024, combining the Deneb consensus layer upgrade with the Cancun execution layer upgrade. Its most impactful change was EIP-4844 (Proto-Danksharding), which introduced blob transactions — slashing the cost for Layer 2 rollups to post data to Ethereum by 80–95%.
What Is Dencun?
The name “Dencun” follows Ethereum’s convention of naming upgrades after astronomical bodies:
- Cancun (execution layer): Named after the Mexican city, responsible for the EVM-level changes including EIP-4844
- Deneb (consensus layer): A star in the Cygnus constellation, responsible for Beacon Chain changes
Key EIPs in Dencun
| EIP | Name | Summary |
|---|---|---|
| EIP-4844 | Proto-Danksharding | Blob transactions for cheap L2 data posting |
| EIP-1153 | Transient Storage | New TSTORE/TLOAD opcodes for within-transaction temporary storage |
| EIP-4788 | Beacon block root | Exposes consensus layer data to EVM |
| EIP-5656 | MCOPY opcode | Efficient memory copying in EVM |
| EIP-6780 | SELFDESTRUCT limit | Restricts SELFDESTRUCT behavior |
| EIP-7516 | BLOBBASEFEE opcode | Returns blob base fee to smart contracts |
EIP-4844 Impact
EIP-4844 was the transformative change:
- Introduced blob-carrying transactions — 128 KB chunks of temporary data
- Created a separate blob gas market with its own base fee
- Blobs pruned after ~18 days; only KZG commitments remain
L2 cost reductions after Dencun:
| Network | Fee Reduction |
|---|---|
| Arbitrum | ~80–90% |
| Optimism/Base | ~85–90% |
| zkSync Era | ~80% |
| Polygon zkEVM | ~85% |
What Came Next
Dencun represented the halfway point toward Full Danksharding. The next major Ethereum upgrade — Pectra (2025) — builds on Dencun by increasing blob capacity and introducing EIP-7702 for account abstraction.
Sources
- Ethereum Foundation Dencun blog post
- EIP-4844.com: blob tracking and education
- L2fees.info: post-Dencun fee comparison