Paste a certificate bundle to check whether it forms a complete, correctly ordered chain. The checker links each certificate to its issuer by comparing subject and issuer names, then reports the order, any missing intermediate, any self-signed root, and any certificate that has expired or is not yet valid. Everything runs in your browser and nothing is uploaded.
It links each certificate to the next by comparing issuer and subject names, then reports the ordering, any gap, any expired or not-yet-valid certificate, whether the first entry is wrongly a CA, and whether a self-signed root has been included unnecessarily.
Does it verify signatures?
No. It checks structure and ordering, which is what actually goes wrong in practice. For cryptographic verification run openssl verify -CAfile root.crt -untrusted intermediate.crt certificate.crt.
Should the root be in my chain file?
No. Clients that trust the root already have it, and clients that do not will not start trusting it because your server sent it. Send the leaf and the intermediates only.
How do I get the chain a live server is sending?
Run openssl s_client -connect example.com:443 -servername example.com -showcerts </dev/null and paste the output here. See fetching a certificate from a server.