Find out if your ISP is hijacking your DNS and showing you sponsored pages.
When you visit a website that doesn't exist, your browser should show a "Site not found" error. Some ISPs intercept these failed lookups and silently redirect you to a sponsored page instead. This is called DNS hijacking — and most people never realise it's happening.
ispcheck detects this in one command and tells you exactly which ISP is doing it.
✗ Bharti Airtel Limited (2401:4900:50:9::7a3) is hijacking your DNS
Got a response for a domain that cannot exist:
http://vteaavshc22753qcv7w411ek.com [200]
Body: "<html>...Verifying…"
Go to the Releases page and download the file for your system:
| System | File |
|---|---|
| Linux (64-bit) | ispcheck-linux-amd64 |
| Linux (ARM, e.g. Raspberry Pi) | ispcheck-linux-arm64 |
| macOS (Intel) | ispcheck-darwin-amd64 |
| macOS (Apple Silicon / M1/M2/M3) | ispcheck-darwin-arm64 |
| Windows | ispcheck-windows-amd64.exe |
Open a terminal, go to where the file was downloaded, and run:
chmod +x ispcheck-linux-amd64 # make it executable (use your filename)
./ispcheck-linux-amd64 # run itDouble-click the .exe file, or open Command Prompt, navigate to the download folder, and run:
ispcheck-windows-amd64.exe
# Run with a random test domain (recommended)
./ispcheck
# Test with a specific domain
./ispcheck somefakedomain.comNo flags, no config, no account needed.
Hijacking detected:
✗ Bharti Airtel Limited (2401:4900:50:9::7a3) is hijacking your DNS
Your ISP is intercepting failed DNS lookups and redirecting you to their own page. The tool shows you which ISP and which DNS server is responsible.
Clean:
✓ ISP is NOT monetizing error pages
Your connection is clean. Failed lookups fail properly without any redirection.
1. Enable DNS-over-HTTPS in your browser (easiest, fixes it just for that browser)
- Firefox: Settings → Privacy & Security → DNS over HTTPS → Select Max Protection → Choose Cloudflare
- Chrome: Settings → Privacy and Security → Security → Use secure DNS → With Cloudflare (1.1.1.1)
2. Use a VPN (fixes it for all traffic)
Any VPN routes your traffic outside the ISP's network entirely.
3. Change DNS on your router (fixes it for all devices on that network)
Set your router's DNS to 1.1.1.1 (Cloudflare) or 8.8.8.8 (Google).
⚠️ This may not work on Airtel — they intercept DNS queries on port 53 regardless of which server you configure.
4. Linux only — DNS-over-TLS system-wide
Edit /etc/systemd/resolved.conf:
[Resolve]
DNS=1.1.1.1#cloudflare-dns.com
DNSOverTLS=yesThen restart: sudo systemctl restart systemd-resolved
This fixes it for all apps on your system, not just the browser.
ispcheck generates a random 24-character domain name (e.g. vteaavshc22753qcv7w411ek.com) that cannot possibly be registered or exist. It then makes an HTTP request to that domain.
- Clean ISP: DNS returns "not found" → connection fails → no response
- Hijacking ISP: DNS returns the ISP's own server IP → connection succeeds → ISP serves a redirect or sponsored page
If a response is received, the tool looks up who owns the DNS server your system is using and names them.
Requires Go 1.24+.
git clone https://github.com/Latencot/ispcheck.git
cd ispcheck
go build -o ispcheck .
./ispcheck- Bharti Airtel (India)
- Reliance Jio (India)
- BSNL (India)
- Comcast (USA) — discontinued
- Verizon (USA) — discontinued
- British Telecom (UK) — discontinued
Built by Latencot