About checkzone.dev

A free, open-source BIND zone file validator

What Is This Tool?

checkzone.dev is a free online tool that validates BIND DNS zone files. If you manage DNS infrastructure using BIND9 (the most widely deployed DNS server software on the internet), you know that a single syntax error in a zone file can take down DNS resolution for an entire domain. This tool lets you catch those errors before they cause problems.

How It Works

The process is straightforward:

1. Paste your zone file into the code editor on the validator page
2. Enter the FQDN (Fully Qualified Domain Name) for the zone, such as example.com
3. Click "Validate" to submit your zone file for checking

Behind the scenes, your zone file is sent to a backend API that runs named-checkzone -- the same validation utility included with BIND9 itself. This means you get the exact same validation that your production DNS server would perform, but without needing to SSH into a server or install BIND locally.

What Gets Checked

The named-checkzone utility validates:

• Zone file syntax and formatting
• SOA (Start of Authority) record correctness
• NS (Name Server) record presence and validity
• Record type syntax (A, AAAA, CNAME, MX, TXT, SRV, PTR, etc.)
• CNAME conflicts (CNAME records cannot coexist with other record types at the same name)
• Missing trailing dots on fully qualified domain names
• TTL (Time To Live) values
• Serial number format in SOA records

Privacy and Security

Your zone file content is sent to our validation API solely for the purpose of running the check. We do not store, log, or retain any zone file data after the validation is complete. See our privacy policy for full details.

That said, if your zone files contain sensitive internal infrastructure details, consider running named-checkzone locally instead. The tool is available in the bind9-utils package on most Linux distributions.

Who Built This

checkzone.dev was built by Jamie Wood, a software engineer who got tired of deploying zone file changes only to find out there was a typo. Rather than keep running named-checkzone manually on a local machine, this tool makes it accessible to anyone with a browser.