> ## Documentation Index
> Fetch the complete documentation index at: https://docs.optimism.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Fjord

> Hardfork registry entry for the Fjord network upgrade, which introduced FastLZ fee estimation and Brotli compression.

<Info>
  **Normative spec:** the [Fjord specification](https://specs.optimism.io/protocol/fjord/overview.html)
  is the canonical definition of this upgrade. This page records activation data
  and operational pointers; it does not restate the spec.
</Info>

Fjord improved fee estimation and batch compression, and added the secp256r1
precompile.

|                                         |                                                                                     |
| --------------------------------------- | ----------------------------------------------------------------------------------- |
| Status                                  | Active                                                                              |
| Governing spec                          | [specs.optimism.io](https://specs.optimism.io/protocol/fjord/overview.html)         |
| Governance approval                     | [proposal](https://gov.optimism.io/t/upgrade-proposal-9-fjord-network-upgrade/8236) |
| Mainnet activation (superchain default) | Wed, 10 Jul 2024 16:00:01 UTC (`1720627201`)                                        |
| Sepolia activation (superchain default) | Wed, 29 May 2024 16:00:00 UTC (`1716998400`)                                        |

## What changed

Per the [spec overview](https://specs.optimism.io/protocol/fjord/overview.html):

* Execution layer: [RIP-7212](https://github.com/ethereum/RIPs/blob/master/RIPS/rip-7212.md)
  precompile for secp256r1 curve support; FastLZ compression for L1 data fee
  calculation; deprecated the `getL1GasUsed` method on the `GasPriceOracle`
  predeploy and the `L1GasUsed` receipt field.
* Consensus layer: constant maximum sequencer drift; Brotli channel
  compression; increased max bytes per channel and max channel bank size.