# L2BEAT ossification

> How long the critical contracts of each tracked project have gone unchanged, and how much value they secured meanwhile, with the exit window where the project has one.

Ossification measures how battle-tested the code securing a project is: the share of recorded code-bug exploits ([published, onchain-verified dataset](https://github.com/l2beat/ossification-dataset)) whose exploited code was younger than the project's critical contracts are today. The clock starts at the ossification genesis, and every critical change resets it. Battle-tested exposure is the value they secured over the unchanged period, in USD-years.

Ossification is not calculated while any critical contract lacks verified source code. Critical changes per year count the trailing 36 months, or the time since the ossification genesis if shorter. The exit window is how long users have to leave before a permitted critical change takes effect; it does not affect ossification.

## Layer 2s (/layer2s/projects/{slug})

- [Arbitrum One](https://l2beat.com/layer2s/projects/arbitrum): ossification 53%, clock since 2026 Aug 31, battle-tested exposure $450.46 M·years of Canonical TVS, 6.3 critical changes / year across 46 contracts, exit window: None
- [BOB](https://l2beat.com/layer2s/projects/bob): ossification 47%, clock since 2026 Sep 16, battle-tested exposure $313.14 K·years of Canonical TVS, 7.6 critical changes / year across 14 contracts, exit window: None
- [Scroll](https://l2beat.com/layer2s/projects/scroll): ossification 44%, clock since 2026 Sep 22, battle-tested exposure $2.61 M·years of Canonical TVS, 8.3 critical changes / year across 51 contracts, exit window: None
- [Morph](https://l2beat.com/layer2s/projects/morph): ossification 44%, clock since 2026 Sep 22, battle-tested exposure $1.03 M·years of Canonical TVS, 11 critical changes / year across 19 contracts, exit window: None
- [Ronin](https://l2beat.com/layer2s/projects/ronin-network): ossification 44%, clock since 2026 Sep 21, battle-tested exposure $0.00·years of Canonical TVS, 9.3 critical changes / year across 14 contracts, exit window: None
- [OP Mainnet](https://l2beat.com/layer2s/projects/op-mainnet): ossification 43%, clock since 2026 Sep 24, battle-tested exposure $73.97 M·years of Canonical TVS, 7.3 critical changes / year across 26 contracts, exit window: None
- [Ink](https://l2beat.com/layer2s/projects/ink): ossification 43%, clock since 2026 Sep 24, battle-tested exposure $3.55 M·years of Canonical TVS, 7.5 critical changes / year across 24 contracts, exit window: None
- [Unichain](https://l2beat.com/layer2s/projects/unichain): ossification 43%, clock since 2026 Sep 24, battle-tested exposure $2.56 M·years of Canonical TVS, 8.7 critical changes / year across 24 contracts, exit window: None
- [Katana](https://l2beat.com/layer2s/projects/katana): ossification 39%, clock since 2026 Sep 30, battle-tested exposure $483.51 K·years of Canonical TVS, 20 critical changes / year across 34 contracts, exit window: None
- [ZKsync Era](https://l2beat.com/layer2s/projects/zksync-era): ossification 38%, clock since 2026 Oct 01, battle-tested exposure $4.74 M·years of Canonical TVS, 14 critical changes / year across 30 contracts, exit window: None
- [Starknet](https://l2beat.com/layer2s/projects/starknet): ossification 33%, clock since 2026 Oct 06, battle-tested exposure $9.80 M·years of Canonical TVS, 13 critical changes / year across 48 contracts, exit window: None
- [Base Chain](https://l2beat.com/layer2s/projects/base): ossification 32%, clock since 2026 Oct 07, battle-tested exposure $66.80 M·years of Canonical TVS, 8.0 critical changes / year across 24 contracts, exit window: None
- [Linea](https://l2beat.com/layer2s/projects/linea): ossification 31%, clock since 2026 Oct 08, battle-tested exposure $2.67 M·years of Canonical TVS, 10 critical changes / year across 18 contracts, exit window: None
- [Mantle](https://l2beat.com/layer2s/projects/mantle): ossification 30%, clock since 2026 Oct 09, battle-tested exposure $12.69 M·years of Canonical TVS, 5.0 critical changes / year across 12 contracts, exit window: None
- [Celo](https://l2beat.com/layer2s/projects/celo): ossification 30%, clock since 2026 Oct 09, battle-tested exposure $45.20 K·years of Canonical TVS, 11 critical changes / year across 30 contracts, exit window: None
- [Lighter](https://l2beat.com/layer2s/projects/lighter): ossification 25%, clock since 2026 Oct 11, battle-tested exposure $14.64 M·years of Canonical TVS, 35 critical changes / year across 5 contracts, exit window: None
- [Taiko Alethia](https://l2beat.com/layer2s/projects/taiko): ossification 24%, clock since 2026 Oct 12, battle-tested exposure $132.71 K·years of Canonical TVS, 27 critical changes / year across 44 contracts, exit window: None

## Privacy protocols (/privacy/projects/{slug})

- [Tornado Cash](https://l2beat.com/privacy/projects/tornado-cash): ossification 99%, clock since 2020 May 18, battle-tested exposure $2.65 B·years of Canonical TVS, 0 critical changes / year across 21 contracts, exit window: Infinite
- [Privacy Pools](https://l2beat.com/privacy/projects/privacy-pools): ossification 83%, clock since 2025 May 22, battle-tested exposure $5.87 M·years of Canonical TVS, 1.3 critical changes / year across 17 contracts, exit window: Infinite
- [Railgun](https://l2beat.com/privacy/projects/railgun): ossification 50%, clock since 2026 Sep 09, battle-tested exposure $10.23 M·years of Canonical TVS, 1.0 critical changes / year across 8 contracts, exit window: 7d
- [zk.money](https://l2beat.com/privacy/projects/zkmoney): ossification 42%, clock since 2026 Sep 25, battle-tested exposure $1.04 K·years of Canonical TVS, 0 critical changes / year across 21 contracts, exit window: Infinite
- [zkAPI](https://l2beat.com/privacy/projects/zkapi): ossification 39%, clock since 2026 Sep 30, battle-tested exposure $71.91·years of Canonical TVS, 0 critical changes / year across 2 contracts, exit window: None

## DeFi protocols (/defi/projects/{slug})

- [Uniswap V3](https://l2beat.com/defi/projects/uniswapv3): ossification 75%, clock since 2026 Mar 06, battle-tested exposure $565.18 M·years of TVL (source: DefiLlama), 1.0 critical changes / year across 8 contracts