A ransomware checker online can help answer “what encrypted my files?” That is a different question from “can my files be decrypted?” Keeping those steps separate prevents false expectations.
What identification tools look at
Ransom notes, filename extensions, sample files and known signatures can help narrow down a ransomware family. Some services can identify a family even when the visible extension is generic.
What identification cannot promise
Correctly identifying STOP/Djvu does not mean the corresponding key is available. Decryption depends on cryptographic and variant-specific conditions.
Protect sensitive sample data
Do not upload confidential originals casually. When a service requests a sample, understand its privacy policy and use non-sensitive encrypted examples where possible.
Use multiple trusted signals
Cross-check the ransom note, extension and a recognized ransomware-response catalog before choosing a decryptor.
Compare catalog approaches in NoMoreRansom vs STOP/Djvu tools.