Why Your Proxy Gets Detected: A Look at IP Disguise
Why sites still recognize you behind a proxy: the full toolkit of detection methods — datacenter IPs, ASN flags, blacklists, consistency signals — and how to test your own disguise score.
A common puzzle: "I'm on a proxy, my IP has changed — why does the site still know I'm not an ordinary user?"
Because sites have never looked at just the IP number itself. This article walks through the mainstream detection methods.
Method One: IP Type — Datacenter or Residential
This is the highest-weighted signal. IP databases (MaxMind, IP2Location, and others) tag every IP range with a type:
| Type | Example | Risk level |
|---|---|---|
| Hosting / Datacenter | Alibaba Cloud, AWS, OVH ranges | High — ordinary people don't browse from datacenters |
| Residential | Home broadband | Low |
| Mobile | Mobile data | Lowest — hundreds of users behind carrier-grade NAT |
| Business | Corporate lines | Medium |
The cheap proxies that cost a few dollars a month are, in the vast majority of cases, datacenter IPs. One glance and the site concludes: this IP belongs to a cloud provider's ASN with a hosting type — flagged as "proxy/crawler" on the spot.
In the disguise score on the IPchase homepage, "IP type" is the very first item.
Method Two: ASN and Organizational Ownership
Behind every IP sits an ASN (autonomous system number). Ordinary residential users carry carrier ASNs like AS4134 (China Telecom) or AS9808 (China Mobile); datacenter IPs carry AS45102 (Alibaba Cloud) or AS16509 (AWS).
Sites don't need a blacklist to pre-filter — the ASN prefix alone does it. The companion signal is reverse DNS (the PTR record): a datacenter IP's PTR often literally reads ecs-xxx.aliyun.com.
Method Three: IP Reputation Blacklists
Blacklist services (Spamhaus, AbuseIPDB, Scamalytics, and others) collect the historical behavior of IP ranges:
- How many crawlers have used this range
- How many spam signups and credential-stuffing attempts came from it
- How many sites have banned it
Cheap shared proxies get passed around among hundreds or thousands of people, and their blacklist records are a horror show. You did nothing wrong, but your IP already has a long rap sheet.
Method Four: Time Zone and Language Consistency
Your IP says United States, but the browser time zone is Asia/Shanghai, the system language is Chinese, and the screen matches a China-market device — pieced together, the site instantly knows "this is a user in China on a US proxy."
None of this takes sophisticated technology — it's cross-referencing a few fields. A truly good disguise means every signal points to the same place.
Method Five: TCP Fingerprinting (JA3/JA4)
During the TCP handshake, the operating system's TCP/IP stack betrays its characteristics (window size, option ordering, and so on), and the cipher suite order in the TLS Client Hello varies by system and browser. These get distilled into JA3/JA4 fingerprints.
The server can cross-check: a connection claiming to be iPhone Safari with a Linux TCP fingerprint — busted.
Method Six: WebRTC and DNS Exits
The two classic leak points are themselves detection signals:
- WebRTC leaks: the real IP and the proxy IP appear at the same time
- DNS leaks: the HTTP exit is in the US while the DNS exit is your carrier
A site doesn't need to "catch" your real IP — spotting the inconsistency is enough to flag you.
How to Test Your Own Disguise Score
Check yourself against each method above:
- IP type and ASN: the IPchase homepage test shows whether your IP is flagged as datacenter
- DNS exit consistency: the "DNS exit" item in the homepage's six-dimension check
- WebRTC exposure: the fingerprint test page
- Time zone/language consistency: the "disguise consistency" item in the fingerprint test
- IP blacklists: paste the IP into AbuseIPDB or similar to check its history
IPchase's disguise score is the quantified combination of items 1–4, and it runs in under a minute.
If You Want a Better Disguise Score, Here's the Direction
- Change IP type: residential and mobile-network proxies are a full tier above datacenter IPs (mind the compliance boundaries — this article covers principles only)
- Fix consistency: align time zone, language, WebRTC, and DNS exit with the IP's location
- Control behavior: make request frequency and access patterns look human
- Accept reality: there is no 100% disguise, only "making the cost of judging you outweigh the benefit"
Summary
Sites detect proxies with a combination: IP type > blacklists > consistency signals > TCP fingerprints. Datacenter IP + time zone mismatch + WebRTC leak — those three account for the majority of exposures.
Run the IPchase test once and see which item is holding your disguise score back.
Check your own network: run a full disguise check on the homepage, or try the fingerprint test.