The safest and most "verified" way to play a randomized 3DS Pokémon game is not to download a pre-made QR code from a stranger, but to create the file yourself. This guarantees the file matches your specific game version and isn't corrupted.

Use a secondary 3DS that doesn't store your primary saves or Nintendo Account. Install the code there first. If it runs for 3+ hours without glitches, it’s likely safe.

For Gen 7 (Ultra Sun/Moon), verified randomizer QR codes have become so stable that competitive players host "blind randomizer tourneys"—everyone scans the same verified code and must adapt on the fly.