Technical reference

Zone Analyzer technical details

This reference documents how Zone Analyzer processes an uploaded DNS export, what stays in your browser, and what is sent to the server when you request screenshots or HTTP status checks.

Author
CategoryUsing the Tools

File parsing

  1. Upload: Files up to 50 MB are accepted. Typical exports are .db, .zone and .txt files in a line-oriented zone format: one complete record per line, with an explicit owner name and a numeric TTL.
  2. Local parsing: The file is read with the browser's FileReader and parsed line by line in the page. Its contents are not uploaded.
  3. Record extraction: Each line becomes a record with a name, TTL, type and data. Blank lines and comments are skipped, and the class field (IN or CHAOS) is ignored. A "; Zone dump of" comment sets the zone name for the records that follow it, so multi-zone dumps keep each record's zone.
  4. Not supported: The parser is not a full RFC 1035 master-file parser. It ignores $ORIGIN, $TTL and $INCLUDE directives, does not reuse the previous owner name on a line that starts with whitespace, does not add the origin to relative names, and does not join parenthesized records that span several lines. A multi-line SOA, for example, appears as several bogus records. Use a one-record-per-line export from your DNS platform or a zone dump tool.
  5. Grid: Records are loaded into a sortable, filterable grid. Your filter settings are remembered in this browser.

What counts as web-facing

A, AAAA and CNAME records are treated as web-facing. Only those records can be sent to Visual Verification or HTTP Status Code Verification. Other record types stay in the grid for review and export.

Visual Verification

  • What is sent: Only the hostnames you select are sent to the server. They are passed to the next page through browser storage, not the URL.
  • How screenshots are taken: Each host is loaded in Cloudflare Browser Rendering at 1280×800, waiting for the page structure to load (up to 15 seconds), and captured as a JPEG.
  • Caching and limits: Screenshots are cached for 1 hour. A site-wide daily screenshot limit applies, and cached screenshots don't count toward it.

HTTP Status Code Verification

  • What is checked: Each selected host is requested and redirects are followed to the final URL. The result shows the final status code, the final URL and whether a redirect happened.
  • Timeouts: A host that doesn't respond within 15 seconds, or can't be reached, is reported as unreachable rather than as an error code.

Export

Export CSV downloads the rows currently visible in the grid, so apply filters first to export a subset.

Analyst notes

Zone Analyzer shows what the export file says. That can differ from what resolvers return if the export is old or the zone has changed. Use Domain Visualizer to compare the file against live DNS.