Paste one citation. RefCheck will check it for a hallucinated or mismatched record and for a retraction notice. This uses one of the five free daily checks, or 1 credit if you are signed in.
The checker searches Crossref and OpenAlex first, then the databases that fit the reference type. You get a verdict (real, real with errors, likely fabricated, or unconfirmed), a corrected citation when the record disagrees, and a retraction flag when one exists.
Need the whole bibliography? Use verify references. Looking specifically for made-up citations? Read hallucinated citation checker.