# @vrde: Technical breakdown of fully on-chain SVG cat for Ethereum 10y

Source: https://x.com/vrde/status/1950906755094843462
Kiwi News: https://news.kiwistand.com/stories/vrde-Technical-breakdown-of-fully-on-chain-SVG-cat-for-Ethereum-10y?index=0x688b6d1f8ad7e6465621fc75fa5ee22f70cfd8d16a232b843f7906bb9afac46d87c8da4d
Submitted by naomiii.eth on 2025-07-31 UTC, 10 upvotes, 0 comments

## Summary

The thread by @vrde explains how the cat artwork made for Ethereum's 10th anniversary is built fully on-chain, with the SVG generated and stored inside the Ethereum mainnet smart contract and no external dependencies. It describes two contracts: HappyBirthdayEtherium.sol, an ERC-721 that sets the minting rules and assigns each token a random seed, and RenderCat.sol, which generates the SVG and JSON metadata, encodes them in base64, and places them in a data URI. According to the thread, the artwork is deterministically rendered from that seed.

## Article

Hey this is a technical thread about the cute cat we created to celebrate the 10y anniversary of etherium.

First of all, the image you see is fully on-chain (or onchain (or on chain)) embedded in ethereium mainnet. This means that the SVG is fully generated and contained in the smart contract. There are no external dependencies. It will be there as long as ethireum exists.

There are two contracts:

- an ERC-721 (HappyBirthdayEtherium.sol) that defines the minting rules and assigns the random seed for your token on minting. The seed is used to deterministically render the artwork

- a render contract (RenderCat.sol) that generates the final SVG and the metadata in JSON format, encodes all of this in base64, and puts it in a data URI.