Bot signals · Web crawler

What is Dead Link Checker?

Dead Link Checker crawls websites to find broken links so they can be fixed. Its Auto Check service runs it through subscribers’ websites on a regular basis.

risk.is_crawler

Official documentation All web crawlers

01 · Profile

Dead Link Checker at a glance.

What to look for in your logs, and what the lookup API returns for its addresses.

Type: Web crawler
User agent: www.deadlinkchecker.com
robots.txt: User-agent: www.deadlinkchecker.com
API flag: risk.is_crawler

A user agent alone never sets a flag. Anyone can claim to be Dead Link Checker; the flag follows the address the request comes from.

02 · In the response

What a match looks like.

A lookup of a Dead Link Checker address sets risk.is_crawler. The flags come with geolocation and network data in the same response, for API keys on every paid plan.

The response says which kind of bot an address belongs to, not which operator. A request that claims to be Dead Link Checker while risk.is_crawler is false should not be trusted as Dead Link Checker.

GET /api/lookup/{ip}?key=YOUR_API_KEY

{
  // … location and network fields …
  "risk": {
    "is_ai": false,
    "is_crawler": true,
    "is_scanner": false
  }
}

03 · Control

Allow or block Dead Link Checker.

robots.txt

User-agent: www.deadlinkchecker.com
Disallow: /

Dead Link Checker follows Disallow and Crawl-delay directives in a www.deadlinkchecker.com group where it can. It does not support wildcards in robots.txt.

To enforce it

robots.txt is a request. Well-behaved bots follow it; impostors using its name don’t.
Firewall, WAF or CDN. Many offer bot rules you can allow or deny by category. Use them to enforce what robots.txt only asks for.
In your app. Look up the client address and allow or deny on risk.is_crawler, alongside the user agent.
Never on the user agent alone. Blocking the name stops only honest clients; allowing it lets anyone in who borrows it.