DPI-CHECKER

🇷🇺 Русский | 🇬🇧 English

Internet Censorship & Blocking Detector — a client-side web tool for detecting DPI/TSPU blocking, checking site availability, detecting geo-restrictions, and checking if an IP is whitelisted on Russia's mobile internet.

What it does

• TCP 16-20 DPI detection — tests 35+ hosting providers using the TCP 16-20 method to detect deep packet inspection interference
• Site availability check — checks 175+ websites across 17 categories (social media, news, messengers, streaming, etc.) with automatic retry on failure
• GeoBlock check — detects whether services (AI assistants, streaming platforms, etc.) are geo-restricted for your actual exit IP, including split-tunnel and policy-based routing scenarios
• IP Whitelist check — checks if any IPv4 address is present in Russia's mobile internet whitelist (zarazaex/TWL), with subnet-level scoring and ISP info via ipapi.is
• Network info — displays your IP, ASN, ISP (with favicon), and geolocation via ipapi.is
• Statistics — saves test history to localStorage and displays availability charts across runs

How DPI detection works

The TCP 16-20 method works as follows:

1. Alive check — verifies the host is reachable via a HEAD request
2. POST 64KB — sends a 64KB POST body; if the connection times out while the host is alive, TSPU/DPI is cutting the stream → status DPI
3. Large URI — sends repeated HEAD requests with ~7KB query strings (~63KB total); timeout → status Suspicious
4. All checks pass → OK

More about the method: github.com/net4people/bbs/issues/490

Provider suite from: hyperion-cs/dpi-checkers

How GeoBlock detection works

Services in the GeoBlock category sit behind Cloudflare. Every Cloudflare-proxied domain exposes a /cdn-cgi/trace endpoint that returns the client IP and country as seen by Cloudflare — readable cross-origin.

The checker fetches https://{domain}/cdn-cgi/trace for each service. Because the request goes to the actual service domain, it follows the user's routing policy — including split-tunnel VPN and domain-based routing rules (e.g. Keenetic, MikroTik). This means the IP and country returned reflect what the service actually sees, not the general browser IP.

The loc field from the trace response is compared against each service's known blocked-country list. If the country matches, the status is GeoBlocked.

chatgpt.com/cdn-cgi/trace response:
  ip=203.0.113.42   ← actual exit IP seen by the service
  loc=PL            ← country seen by the service → checked against blockedIn list
  colo=WAW          ← Cloudflare datacenter

How IP Whitelist check works

Checks whether an IPv4 address is present in the zarazaex/TWL whitelist — a crowdsourced list of IPs accessible via Russian mobile internet during connectivity restrictions.

Three sources are checked in parallel:

Source	Description	Max score
verified.txt	Direct IP match in the verified list	95%
subnets.c.json	IP falls within a verified subnet	up to 90%
subnets.json	IP falls within a raw (unverified) subnet	up to 70%

Score formula for subnet matches: maxScore × (base + 0.4 × subnet_fill%), where base is 0.5 for verified subnets and 0.3 for raw subnets. The final score is the maximum across all sources.

ISP information (org name, ASN, country, city) is fetched from ipapi.is.

Site check statuses

Status	Meaning
OK	Accessible
Blocked	Unreachable (connection failed or timed out after 3 attempts)
DPI	Host alive but POST 64KB timed out — DPI detected
Suspicious	Large URI request timed out — possible DPI
GeoBlocked	Reachable, but exit IP country is on the service's blocked-country list

Configuration

Sites and categories are defined in src/shared/config/config.ts. Each category has an optional checker field:

export const CONFIG = [
  // GeoBlock services — uses cdn-cgi/trace checker with per-service geo-block lists
  {
    id: 'geoblock',
    en: 'GeoBlock',
    checker: 'cdn-trace',
    sites: [
      {
        d: 'chatgpt.com',
        name: 'ChatGPT',
        blockedIn: ['CN', 'RU', 'BY', 'KP', 'CU', 'IR', 'SY', 'VE', 'MM'],
      },
    ],
  },

  // DPI providers — uses TCP 16-20 checker
  {
    id: 'providers',
    en: 'Providers (TCP 16-20)',
    sites: [{ d: 'example.com', flag: 'US', name: 'Provider' }],
  },

  // All other categories — uses simple HTTP reachability checker
  {
    id: 'social_intl',
    en: 'Social Media (International)',
    ru: 'Соцсети (международные)',
    sites: [{ d: 'twitter.com', name: 'X / Twitter' }],
  },
];

Checkers

Category	Checker	File
providers	TCP 16-20 DPI detection	src/shared/api/check-dpi-provider.ts
geoblock	cdn-cgi/trace + geo-block verdict	src/shared/api/check-cdn-trace.ts
all others	Simple HTTP fetch with 2 retries	src/shared/api/check-site.ts

Stack

• Next.js 16 / React 19
• Mantine UI v9
• next-intl (EN / RU, locale in URL: /en/, /ru/)
• TypeScript