DNS 記錄說明器
選擇任一 DNS 記錄類型（A、AAAA、CNAME、MX、TXT、NS、SOA、CAA、PTR、SRV），取得詳細說明與範例。
A — IPv4 Address
Maps a hostname to a 32-bit IPv4 address. The most fundamental DNS record — it tells browsers where to send requests.
Format
<hostname> <TTL> IN A <IPv4 address> Examples
example.com. 3600 IN A 93.184.216.34www.example.com. 300 IN A 93.184.216.34 Common uses
- Primary name-to-IP mapping for websites
- Round-robin load balancing (multiple A records)
- Pointing a root domain to a hosting server
AAAA — IPv6 Address
Maps a hostname to a 128-bit IPv6 address. The IPv6 equivalent of the A record.
Format
<hostname> <TTL> IN AAAA <IPv6 address> Examples
example.com. 3600 IN AAAA 2606:2800:220:1:248:1893:25c8:1946 Common uses
- IPv6 connectivity for dual-stack servers
- Required for full IPv6 support alongside A records
CNAME — Canonical Name
Creates an alias from one hostname to another. The resolver looks up the target name and returns its address.
Format
<alias> <TTL> IN CNAME <canonical name> Examples
www.example.com. 3600 IN CNAME example.com.blog.example.com. 300 IN CNAME example.github.io. Common uses
- Pointing www to the root domain
- CDN integration (point subdomain to CDN hostname)
- Platform aliases (e.g. GitHub Pages, Netlify)
MX — Mail Exchange
Specifies the mail servers that accept email for a domain. Multiple MX records with different priorities provide redundancy.
Format
<domain> <TTL> IN MX <priority> <mail server> Examples
example.com. 3600 IN MX 10 mail1.example.com.example.com. 3600 IN MX 20 mail2.example.com. Common uses
- Routing incoming email to the correct server
- Google Workspace, Microsoft 365, or custom mail server setup
- Lower priority number = higher preference
TXT — Text
Stores arbitrary text strings. Used for domain verification, email authentication (SPF, DKIM, DMARC), and other machine-readable data.
Format
<domain> <TTL> IN TXT "<text string>" Examples
example.com. 3600 IN TXT "v=spf1 include:_spf.google.com ~all"example.com. 3600 IN TXT "google-site-verification=abc123" Common uses
- SPF records to authorise outgoing mail servers
- Domain ownership verification for Google, AWS, etc.
- DMARC and DKIM email authentication
NS — Name Server
Identifies the authoritative name servers for a domain. Delegating a subdomain uses NS records.
Format
<domain> <TTL> IN NS <name server> Examples
example.com. 86400 IN NS ns1.example.com.example.com. 86400 IN NS ns2.example.com. Common uses
- Identifying which servers hold DNS records for a domain
- Delegating subdomain DNS to a different provider
SOA — Start of Authority
Contains administrative information about a DNS zone: primary name server, responsible party, and refresh parameters.
Format
<domain> <TTL> IN SOA <primary NS> <admin email> <serial> <refresh> <retry> <expire> <min TTL> Examples
example.com. 86400 IN SOA ns1.example.com. admin.example.com. 2024010101 86400 7200 3600000 300 Common uses
- Zone transfer control between primary and secondary servers
- Serial number increments trigger zone replication
- Negative caching TTL (minimum field)
CAA — Certification Authority Authorization
Specifies which certificate authorities are allowed to issue SSL/TLS certificates for the domain.
Format
<domain> <TTL> IN CAA <flags> <tag> "<value>" Examples
example.com. 3600 IN CAA 0 issue "letsencrypt.org"example.com. 3600 IN CAA 0 issuewild ";" Common uses
- Preventing unauthorised CAs from issuing certificates for your domain
- Restricting wildcard certificate issuance
- Mandatory CA compliance requirement for many auditors
PTR — Pointer (Reverse DNS)
Maps an IP address back to a hostname. Used in reverse DNS lookups (the .in-addr.arpa zone).
Format
<reversed IP>.in-addr.arpa. <TTL> IN PTR <hostname> Examples
34.216.184.93.in-addr.arpa. 3600 IN PTR example.com. Common uses
- Email deliverability — mail servers check PTR records to validate senders
- Network diagnostics and logging
- Security analysis and IP reputation
SRV — Service Locator
Specifies the location (hostname and port) of a service. Used by protocols like SIP, XMPP, and Microsoft services.
Format
_<service>._<proto>.<domain> <TTL> IN SRV <priority> <weight> <port> <target> Examples
_xmpp-client._tcp.example.com. 86400 IN SRV 10 5 5222 xmpp.example.com. Common uses
- VoIP/SIP server discovery
- XMPP (Jabber) client-to-server connections
- Microsoft Teams, Skype for Business, and Exchange Autodiscovery
How to use
- Select a DNS record type from the dropdown above.
- Read the description, format reference, and examples to understand what the record does.
- Use the examples as a template when configuring DNS in your registrar or DNS provider.
Related network tools
- WHOIS Formatter — parse raw WHOIS output including name server info
- SSL/TLS Grade Info — understand CAA records and certificate security
- HTTP Headers Decoder — inspect headers related to DNS prefetch and preconnect
常見問題
- Is this DNS explainer free?
- Yes, completely free with no signup and no usage limits.
- Does my data leave my device?
- No. This is a reference page — no data is sent anywhere.
- Does it work on mobile?
- Yes. The tool is mobile-first and works on iPhone Safari and Android Chrome.
Last updated: By jarvisbox