Checksum Calculator — CRC32, MD5 & SHA
Compute every common checksum at once and compare against an expected value. This is usually the missing step when a game rejects an edited save.
Intended for your own single-player save files. Editing saves in multiplayer or online games breaks their terms of service and can get your account banned. Always keep a backup of the original file before you change anything.
Many saves store a checksum so the game can reject edited files. After changing a save you usually need to recompute the checksum over the right byte range — often everything except the checksum field itself — and write it back. CRC-32 is by far the most common, and note that games frequently store it byte-reversed.
Frequently Asked Questions
Why does my game reject an edited save?
Because most saves store a checksum, and the game recalculates it on load. Change one byte and the stored checksum no longer matches, so the save is treated as corrupt. You need to recompute it over the correct byte range and write the new value back.
Which algorithm do save files use?
CRC-32 by a wide margin — it is fast and only four bytes. MD5 and simple byte sums also appear. SHA is rare in saves because it is slower and produces a much longer value.
Why is CRC-32 shown twice?
Because byte order matters. A CRC of 0x12345678 is very often stored in a file as 78 56 34 12, little-endian. The second row gives you that reversed form so you can match what is actually in the file.
Which bytes should the checksum cover?
That depends entirely on the format, and finding out is the hard part. A common pattern is every byte except the checksum field itself. Compare a known-good save's stored value against checksums of different ranges until one matches.
Why is MD5 here if it is broken?
MD5 is broken for security — you can construct two files with the same hash — but it is perfectly fine as an integrity check, and plenty of older games use it. Never use it for passwords or signatures.