Forward-confirmed reverse DNS

A verification check that an IP address's hostname belongs to the operator, and that the hostname points back to the same address.

Why it matters

This check is the reliable way to confirm a visitor really comes from the company it names, for operators that publish their hostnames. You rarely need to run it by hand: good bot protection and agent monitoring do it for you. What matters is that your rules rely on it, rather than on a name anyone can type.

More terms in getting in

• robots.txt A file at the root of your site that tells crawlers and agents which pages they may visit.
• Bot protection Services such as Cloudflare, Akamai or DataDome that block or challenge automated visitors.
• CDN Content delivery network: the service that sits in front of your site and delivers it quickly around the world.
• CAPTCHA or challenge A test that tries to tell people from bots, such as picking out images or waiting on a “checking your browser” page.
• Rate limit A cap on how many requests a visitor can make in a given time.
• Verification Checking that a visitor claiming to be a known agent really is, using the proof its operator publishes: IP ranges, reverse DNS or a signature.

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