A domain-validated certificate (DV) is an X.509 digital certificate typically used for Transport Layer Security (TLS) where the identity of the applicant has been validated by proving some control over a DNS domain.
The sole criterion for a domain-validated certificate is proof of control over a domain. Typically control over a domain is determined using one of the following:
- Response to email sent to the email contact in the domain's whois details
- Response to email sent to a well-known administrative contact in the domain, e.g. (admin@, postmaster@, etc.)
- Publishing a DNS TXT record
- Publishing a nonce provided by an automated certificate issuing system
A domain-validated certificate is distinct from an Extended Validation Certificate in that this is the only requirement for issuing the certificate. In particular, domain-validated certificates do not assure that any particular legal entity is connected to the certificate, even if the domain name may imply a particular legal entity controls the domain.
Most web browsers may show a lock (often in grey, rather than the green lock typically used for an Extended Validation Certificate) and a DNS domain name. A legal entity is never displayed, as domain-validated certificates do not include a legal entity in their subject.
- Mozilla Firefox historically showed domain validated certificates with a grey lock, but was modified to show a green lock for DV connections after Mozilla launched Let's Encrypt (which only provides domain-validated certificates).
- Safari shows domain-validated certificates with a grey lock.
- Microsoft Edge displays domain-validated certificates with a hollow grey lock.
- Chrome and Chromium display a green lock.
As the low assurance requirements allow domain-validated certificates to be issued quickly without requiring human intervention, domain-validated certificates have a number of unique characteristics:
- Domain-validated certificates are used in automated X.509 certificate issuing systems.
- Domain-validated certificates are often cheap or free.
DV does not authenticate the certificate holder as a real world entity
Domain validation reduces validation requirements for both Certificate Authorities and applicants. However Domain Validation does not assert the certificate belongs to a specific real world entity, but rather a DNS domain name - whether that domain has any association with a company or otherwise.