How can you tell if your copy of a game is good or bad? The Redump project can answer that, and here's how it works.
Every game has a digital fingerprint called a "hash", and when two files have the same hash you know they're identical. The Redump project records the hashes of many videogames. Just compare your game's hash to the one in Redump and if they match, your copy's good!
To guarantee the best quality each PS1 game at Vimm's Lair is scanned nightly with the latest Redump data. Why nightly? Redump contributors aren't perfect, so over time corrections are made which changes the hash. Those changes are flagged for review, so if you see a flagged game and know where to find the new copy please lend a hand and upload it.