How to use the DNS lookup
- Enter a domain name such as
example.com(a full web address works too; only its host name is used), or an IP address for a reverse lookup. - Choose which records to look up. Common records asks for the eight types most sites use.
- Each record type is listed with its name, its TTL and its value, and notes point out common problems, such as two SPF records or a missing DMARC policy.
What the record types mean
- A and AAAA: the IPv4 and IPv6 addresses the name points to.
- CNAME: an alias. The name is another name’s nickname, and resolves to whatever that name resolves to.
- MX: the servers that receive the domain’s email, tried in order of priority (lowest first).
- NS: the name servers that hold the domain’s records.
- TXT: free text, used for SPF (which servers may send the domain’s email), site ownership checks and DKIM keys.
- SOA: the zone’s administrative record: its primary name server, contact, serial number and timers.
- CAA: which certificate authorities may issue SSL certificates for the domain.
- SRV: where a service runs, for names such as
_sip._tcp.example.com. - DMARC: the TXT record at
_dmarc.example.comthat tells receivers what to do with mail failing SPF and DKIM.
TTL and caching
The TTL (time to live) is how long resolvers may keep a record before asking again. After you change a record, some visitors can see the old value until the old TTL runs out. Lower the TTL a day before a planned change, and raise it again afterwards.
Where the answers come from
The lookup is made by this site’s server, through its DNS resolver, so you see what the internet sees rather than your own computer’s cache. Resolvers cache too: a record changed a few minutes ago may still show its old value here until its TTL expires. The name you enter is sent to this site to run the lookup; the result is kept for about a minute so that repeating the same lookup is instant.