The tool supports all the common formats for NES/SNES/GBA/N64/TG-16/SMS/Genesis/Neo Geo/PS1 saves found on sites like GameFAQs.
You can check it out at https://savefileconverter.com/
I found that saves on those sites are often in largely-unhelpful legacy formats like DexDrive or Wii Virtual Console. This site will convert those files into "regular" saves that can be directly loaded by an emulator. Many flash carts can also use files in this same format, and they can also be written to real carts/memory cards.
There's also a couple of firsts here: TG-16 saves in Wii VC format couldn't be loaded by any save converter that I'm aware of, and JanErikGunner on github recently figured out the format and this is the only implementation I'm aware of. Also, eeprom saves within an N64 dexdrive/controller pak file used to require editing in a hex editor to be usable in an emulator and this tool will output a file that requires no editing.
I also included a list of places I've found to download save files, which I've found useful when searching for a particular game.
Now you can unlock all the cheats in GoldenEye 64, unlock all the extra levels in Yoshi's Island on SNES, or unlock the 4 swords palace in Link to the Past on GBA.
Everything is open source and the code can be found at https://github.com/euan-forrester/save-file-converter
Have I missed any formats? Anything else I should add?