DNS Zone File Validator | BIND Syntax Check

DNS zone file validator that checks BIND records for syntax errors, bad TTLs, missing SOA fields and unterminated names. Runs offline. Free. Designed specifically for developers and professionals, this free online validator runs entirely in your browser to process tasks quickly and securely. Enjoy unlimited usage with no data tracking and no registration required.

Also known as: dns zone file validator · bind zone file checker · validate dns zone file online · zone file syntax checker · check soa serial number · dns record validator online · bind zone file linter · rfc 1035 zone file check

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Zone File Input

Validation Report

Syntax errors, RFC violations and record counts will appear here.

About DNS Zone File Validator

Check a BIND zone file for the mistakes that break a zone load before you push it to a name server. The validator parses master file syntax the way named-checkzone does, then reports syntax errors, malformed record data and RFC violations with the line number that caused each one, entirely in your browser.

Key Features

Parses BIND master file syntax including $ORIGIN, $TTL, multi-line parenthesized records and semicolon comments
Validates rdata per record type: IPv4 for A, IPv6 for AAAA, preference plus exchange for MX, four fields for SRV, quoted strings for TXT and CAA
Flags the RFC 1034 rule that a CNAME cannot share a name with any other record, and that a CNAME cannot sit at the zone apex
Checks the SOA block for all seven fields, a nonzero serial, an @-free contact address and sane refresh, retry and expire ordering
Reports missing apex NS records, duplicate records, TTLs above the RFC 2181 maximum and relative names used with no $ORIGIN
Filter findings by message, error code or line number, then copy or download the full text report

Use Cases

Catch a typo in a zone file before a production DNS change takes a company site offline
Review a zone exported from Route 53, Cloudflare or GoDaddy before importing it into a self-hosted BIND or Knot server
Confirm a new CAA or SRV record is well formed when adding Let's Encrypt issuance or a SIP service
Check a pull request that edits zone data when your team keeps DNS in Git and applies it from CI
Teach the master file format to a junior engineer without giving them access to a live name server
Verify that an incremented SOA serial and the refresh timers will actually propagate to secondaries

Supported Formats

BIND master file (.zone, .db)

RFC 1035 master file format

SOA, NS, A, AAAA, CNAME, MX, TXT, SPF, PTR, SRV, CAA, DNAME

DNSSEC types: DS, DNSKEY, RRSIG, NSEC, NSEC3, CDS, CDNSKEY

Modern types: TLSA, SSHFP, SVCB, HTTPS, URI, NAPTR

Related Keywords

dns zone file validator

bind zone file checker

validate dns zone file online

zone file syntax checker

check soa serial number

dns record validator online

bind zone file linter

rfc 1035 zone file check

Why does my zone fail with a CNAME and other data error?

RFC 1034 section 3.6.2 says that if a name has a CNAME record, it can have no other records at all. A resolver that follows the CNAME would have no way to decide which answer wins, so BIND refuses to load the zone rather than serve an ambiguous one. This bites most often at the apex, where people try to point example.com at a CDN with a CNAME while the zone already has SOA and NS records there. Use an A or AAAA record at the apex, or a provider-specific flattening record such as ALIAS or ANAME, and keep CNAME records on subdomains like www.

Your zone file never leaves this page

Parsing and validation run in JavaScript in your browser. Nothing is uploaded, logged or sent to a DNS server, so internal zones with private hostnames and addresses stay on your machine.

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Frequently asked questions

What is DNS Zone File Validator used for?

DNS zone file validator that checks BIND records for syntax errors, bad TTLs, missing SOA fields and unterminated names. Runs offline. Free.

Is DNS Zone File Validator free to use?

Yes. DNS Zone File Validator is completely free with no usage limits, and there is no paid tier required to use it.

Do I need an account to use DNS Zone File Validator?

No. DNS Zone File Validator works immediately in your browser with no signup, login, or email address required.

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