About EZ ROM Patcher
EZ ROM Patcher is a free browser-based ROM patching tool built on Rom Patcher JS, the open-source MIT-licensed engine by Marc Robledo. All patching happens on your device. The engine is pulled directly from its GitHub repository and automatically verified before every deploy.
Credits
The patching engine is Rom Patcher JS by Marc Robledo, released under the MIT licence. It implements every patch format this site supports, and the work here is a wrapper around it rather than a reimplementation.
The checksum tool uses the CRC32 and MD5 implementations from Marc Robledo’s SFV Checker, also MIT-licensed. SHA-1 comes from the browser’s built-in Web Crypto API.
Rom Patcher JS also depends on zip.js by Gildas Lormeau for archive handling, and Octicons by GitHub for interface icons.
How this site stays current with upstream
The engine is not copied and forgotten. Every build fetches the current source directly from the upstream GitHub repository, so improvements and new format support land here without a manual port. If GitHub cannot be reached, the build falls back to the last known-good copy committed alongside this site rather than shipping something it has not seen.
That would be risky on its own, so each build runs an automated gate before anything ships. It round-trips real patches through the freshly fetched engine in seven formats, checks that hashes match standard test vectors, exercises the copier-header path end to end, and confirms the APIs this site depends on still exist. If any check fails, the build stops rather than publishing a patcher that cannot patch.
The engine is not quite untouched, and it would be dishonest to imply otherwise. Two lines are rewritten as it is fetched. The first makes it resolve its own Web Workers from an absolute path, because upstream resolves them relative to the current page and this site puts the patcher on more than one route. The second repairs a typo, headerInfo.fileSize where the property is headerInfo.size, which stopped the patcher from stripping a copier header it had added itself: ticking Add header returned a file 512 bytes longer than it should have been, carrying a header the user did not ask for and a checksum that would not match the one in a hack’s readme.
Neither is a hand edit. Both are declared as rules that have to match the upstream source exactly once, each with the reasoning for it written alongside, and the build fails if either stops matching, which is how we find out that upstream has fixed it and the rule can be deleted. Both have been written up as a bug report for the upstream project, with reproductions and suggested diffs.
What this site will not do
We do not host ROMs, link to ROM sites, or help you find copyrighted games. This is a file utility. Supplying the ROM is your responsibility, and dumping it from hardware you own is the lawful route.
Frequently asked questions
Is EZ ROM Patcher open source?
The patching engine is open source. Rom Patcher JS by Marc Robledo is MIT-licensed and available on GitHub, and this site vendors it as published apart from a short list of small corrections: an absolute asset path so the engine finds its own files on nested pages, a property-name fix for an upstream typo that left an unwanted 512-byte header on the output, the removal of two font imports that fetched from Google on every page without ever being used, and a dropped argument that stopped a multi-entry RUP patch from selecting the entry matching your ROM. Each one is recorded in the build with the reasoning behind it, the patching bugs have been prepared as a report for the upstream project, and the build fails if any of them stops matching, so an upstream fix cannot go unnoticed.
How often is the patching engine updated?
Every build pulls the latest upstream source, so a deploy picks up whatever Marc Robledo has published. An automated verification gate runs first and blocks the build if the new version fails its round-trip patch tests.
Is this site affiliated with Marc Robledo?
No. It uses his MIT-licensed open-source engine with attribution, as the licence permits and the project’s documentation encourages, but it is an independent site.