SRV record
An SRV (service) record tells software which host and port run a particular service for a domain, with priorities and weights for backups and load sharing. Calendar and contacts apps, SIP phones, XMPP chat, Minecraft, Microsoft Teams and email client autoconfiguration all use SRV records.
| Record type | SRV |
|---|---|
| Type number | 33 |
| Used for | Services |
| How common | Common |
| Defined in | RFC 2782 |
Format
_<service>._<protocol>.<name> <ttl> IN SRV <priority> <weight> <port> <target>
| Field | What it means | Accepted values |
|---|---|---|
| Service and protocol | The name says which service and transport this is for. | _sip._tcp, _imaps._tcp, _minecraft._tcp, _xmpp-client._tcp. |
| Priority | Lower is tried first, as with MX. | 0 to 65535. |
| Weight | Among targets with the same priority, the share of traffic each gets. | 0 to 65535. 0 means no preference. |
| Port | The port the service listens on. | 0 to 65535. |
| Target | The host running the service. . means not available here. | A host name with an A or AAAA record, not a CNAME. |
Check an SRV record
Type or paste a record in zone-file form (name, TTL, type, value) or just its value. Each part is explained as you type.
A valid SRV record.
| Part | What it means |
|---|---|
| Name_sip._tls | A service name. Underscore names hold records for a protocol (such as _dmarc or _sip._tcp), not a website. |
| TTL3600 | Resolvers may keep this answer for 1 hour before asking again. Changes can take that long to reach everyone. |
| ClassIN | Internet. Every record you'll write uses IN. |
| TypeSRV | Where a service runs: host and port. |
| Priority100 | Lower is tried first, like MX priority. |
| Weight1 | Among servers with the same priority, higher weight gets a bigger share of traffic. |
| Port443 | The service listens on port 443. |
| Targetsipdir.online.lync.com. | The host that runs the service. Must have an A or AAAA record, not a CNAME. |
Examples
Microsoft Teams (SIP)
_sip._tls 3600 IN SRV 100 1 443 sipdir.online.lync.com.
One of the records Microsoft 365 asks for.
Minecraft server on a custom port
_minecraft._tcp.play 3600 IN SRV 0 5 25566 mc.example.com.
Players type play.example.com and the game finds port 25566.
Two servers sharing load
_xmpp-client._tcp 3600 IN SRV 10 60 5222 a.example.com. _xmpp-client._tcp 3600 IN SRV 10 40 5222 b.example.com.
Same priority, so roughly 60% of clients go to a and 40% to b.
Service not offered
_imap._tcp 3600 IN SRV 0 0 0 .
Clients shouldn't try plain IMAP here.
See it on a real domain
TTL
3600. How TTL works
Common mistakes
- Leaving out the underscores or the protocol label: it's _sip._tcp, not sip.
- Pointing the target at a CNAME or an IP address.
- Some dashboards have separate Service, Protocol and Name fields; filling the whole name into Name as well gives _sip._tcp._sip._tcp.
At your DNS host
- Cloudflare: separate fields for service, protocol, name, priority, weight, port and target.
- Route 53: one value: 10 60 5060 sip.example.com.
- GoDaddy: Service and Protocol fields take the underscore names, such as _sip and _tcp.
Questions
What's the difference between priority and weight?
Priority picks which group of servers is used first (lowest wins). Weight shares traffic within that group.
Do browsers use SRV records?
No. Websites use A, AAAA and HTTPS records. SRV is for other protocols.
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