SSLWatchSSL certificate chain explained (leaf, intermediate, root)
What a certificate chain is, why "incomplete chain" errors happen and how to fix them.
Browsers trust a small set of root certificates. Roots sign intermediate certificates, and intermediates sign your site's leaf certificate.
Why chains break
If your server sends only the leaf and not the intermediate, some browsers and most APIs/curl fail with "unable to get local issuer certificate".
How to fix
Install the "full chain" file from your certificate authority (for Let's Encrypt, fullchain.pem). Then re-run our checker – the chain section should list leaf → intermediate.