Three validation levels, differing in what the issuer checked before issuing.
DOMAIN VALIDATED
The issuer confirmed you control the domain, usually by checking a file on the server or a DNS record. Issued in minutes, automatically.
Free AutoSSL certificates are domain validated. So are most paid certificates.
ORGANISATION VALIDATED
The issuer additionally verified the legal entity behind the domain: company registration, address, sometimes a telephone check. Takes days and requires documentation.
EXTENDED VALIDATION
The most rigorous checks on the organisation, following a defined standard. Takes longest and costs most.
WHAT DIFFERS IN THE BROWSER
Almost nothing. Browsers once displayed a green bar with the company name for EV certificates. They no longer do. A visitor cannot distinguish the three without inspecting the certificate manually.
WHAT DIFFERS IN ENCRYPTION
Nothing. All three encrypt identically.
WHICH TO CHOOSE
Domain validated for almost every site. Organisation or extended validation only where a partner, regulator or payment processor specifically requires it in writing.
