Every check in ReferenceLib is an automated comparison against a public scholarly database. Nothing is verified by a person, and nothing is verified by a language model. Here is exactly what each label means and where it comes from.
Results in Find Evidence and Evidence My Paragraph come from OpenAlex, a free, open scholarly index. Each result carries a peer-review label: "Likely peer reviewed" is based on the source type OpenAlex records for the journal. That label is upgraded to "Peer reviewed, verified" only when DOAJ (the Directory of Open Access Journals) independently confirms the journal itself is listed as a genuine, open-access, peer-reviewed publication. Preprints are excluded from results by default. A source with unknown peer-review status is never shown as verified.
The Verify a Reference tab checks a pasted DOI, title or full reference against Crossref, the official DOI registration database publishers use. A DOI match confirms the reference exists exactly as recorded by the publisher. Where no DOI is found, the tool falls back to a title search against the same database and says so explicitly, since a title match is lower confidence than a DOI match.
A verified label confirms a source exists in these public databases and meets the stated evidence criteria. It does not guarantee that a specific assessor, module or institution will accept the source, and it does not check whether the source actually supports the point you are using it for. That judgement stays yours.