# Calculation of proxy contract storage slot

**URL:** <https://forum.openzeppelin.com/t/calculation-of-proxy-contract-storage-slot/30745>\
**Category:** Upgrades\
**Tags:** proxies\
**Created:** [July 29, 2022, 9:44am UTC](https://forum.openzeppelin.com/t/calculation-of-proxy-contract-storage-slot/30745 "2022-07-29T09:44:59Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![frangio](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.openzeppelin.com/frangio/32/15251_2.png) [@frangio](https://forum.openzeppelin.com/u/frangio)\
**Post date:** [August 10, 2022, 4:27pm UTC](https://forum.openzeppelin.com/t/calculation-of-proxy-contract-storage-slot/30745/2 "2022-08-10T16:27:52Z")

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See:

> **[EIP-1967: Standard Proxy Storage Slots](https://ethereum-magicians.org/t/eip-1967-standard-proxy-storage-slots/3185/4?u=frangio)**
>
> If you have keccak256('eip1967.proxy.implementation') the preimage is known, it is 'eip1967.proxy.implementation'. If you subtract one you get a random number with unknown preimage because keccak256 is a cryptographic hash.

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