About Check-Host.cc

Check-Host.cc is a free, ad-free, distributed network monitoring tool. Users trigger real-time checks — ping, HTTP, TCP, UDP, DNS, and MTR — from our global nodes. We do not crawl websites; every probe is a single on-demand request initiated by a human user.

Information for Security Systems & Cloudflare

If your firewall, WAF, or Cloudflare rule is blocking our probes, the information below will help you identify and whitelist legitimate Check-Host traffic.

User-Agent

Check-Host check-host.cc

All HTTP checks sent by our nodes use the following User-Agent. You can use this to identify and whitelist our requests at the application layer.

Traffic Behaviour

Our nodes never crawl. Each probe is a single HTTP request (or ICMP/TCP/UDP packet) — either triggered by a user on the website, or sent as a scheduled monitoring probe for a registered domain.

Single request per probe — no recursive crawling
User-triggered checks or scheduled monitoring probes for registered domains
No session cookies, no JavaScript execution
HEAD or GET requests for HTTP checks

Node IP List

All egress IPs used by our check nodes are listed at the URL below in plain-text format, one per line. This list is updated automatically when nodes are added or removed.

check-host.cc/ips

Cloudflare — Global WAF Rule

To whitelist Check-Host across your entire Cloudflare zone in one rule, use any of the identifiers below. Combine them with OR for maximum coverage. This covers both on-demand checks and monitoring probes.

Match by User-Agent

http.user_agent contains "Check-Host"

Match by IP List

check-host.cc/ips

Import check-host.cc/ips into a Cloudflare custom IP List, then reference it in your rule expression.

Example WAF expression

(http.user_agent contains "Check-Host") or (ip.src in $check_host_ips)

Paste this into Security → WAF → Custom Rules → Edit expression.

Check Types

The following probe types are available on demand. Monitoring automatically runs these probes on a schedule for registered domains.

Ping (ICMP)

ICMP Echo Request to the target host. Reports round-trip time and packet loss.

HTTP/HTTPS

Single HTTP GET/HEAD request. Reports status code, response time, and redirect chain.

TCP Connect

TCP handshake to a given host and port. Reports connection time or timeout.

UDP Probe

UDP packet sent to a host and port. Useful for checking DNS or game servers.

DNS Lookup

DNS query performed from the node. Reports resolved IPs and query time.

MTR Trace

Combined traceroute and ping. Shows each network hop and its latency.

Uptime Monitoring

Coming soon

Register a domain and Check-Host will probe it automatically at regular intervals from our global nodes. Each monitoring probe is a single lightweight request — identical to a user-triggered check, just scheduled. No crawling, no indexing, no JavaScript execution. Probes appear with the same User-Agent and node IPs as regular checks.

Automated periodic probes — single request per interval
Same User-Agent and node IPs as on-demand checks
No data crawled or indexed — only availability & latency recorded
Alerts on downtime or response anomalies

Rate Limits

To ensure fair use and protect targets from abuse, checks are throttled per requesting IP and per target host. Live checks (continuous mode) have tighter limits than single checks.

Window	Per IP — Normal	Per IP — Live	Per Target — Normal	Per Target — Live
10 seconds	6	2	11	3
1 minute	30	7	39	13
1 hour	250	50	200	50
1 day	—	—	2,000	500

Need higher limits for production use or monitoring at scale? You can request an API key via our contact page — API keys receive significantly increased quotas.

Request an API key →

API Documentation

Check-Host.cc provides a public JSON API. You can trigger checks and read results programmatically.

docs.check-host.cc

Contact

For abuse reports, whitelisting requests, partnerships, or general questions, please use our contact page.

Contact →

Machine-Readable Data

A JSON summary of this information is available for automated systems.

check-host.cc/about.json