dns.pizza
Domain Intelligence Report

web4u.cz

Full ownership history report — $29 at AboutUsCompare
Gathering intelligence... (12/12)
DNS
WHOIS
Security
Email
DNSSEC
Threats
Deliverability
SSL/TLS
HTTP
Tech Stack
Subdomains
Archive
Safe
Healthy
no attacks or spoofing
Up
HTTP 200
reachable and responding
Right
Set up Page Watch
it is what it is
Ready
22d to renew
you see what's coming
Outline
WHOIS
Web4U s.r.o. · registered 25 years ago · expires Dec 16, 2026
DNS
1 A · 1 MX · 2 NS · 1 CAA · 1 PTR · 1 SOA · 4 TXT · 1 AAAA
SSL/TLS
Let's Encrypt · TLSv1.3 · ⚠ 22d left · 2 SANs
Email Auth
SPF ✓ · DKIM ✓ · DMARC ✓ (p=reject)
DNSSEC
signed · valid chain of trust
Tech Stack
Host: Web4U s.r.o. · Email: Self-hosted · OpenResty
HTTP
2 redirect → 200 · HSTS ✓ · CSP ✓ · X-Frame ✓ · Nosniff ✗
Security
B (190/225) · 1 high
Threats
risk: none
Deliverability
96% A+ (96/100 points) · 1 MX · 2 IPs · 2 issue(s)
Subdomains
10 found · 97 answered (15 timed out) — imap, mail, mx, mx2, pop, pop3 +4 more
Web Archive
first snapshot 2001-02-21 · 25y archived
DNS Recordschecked 2.4d ago
Details
1 A · 1 MX · 2 NS · 1 CAA · 1 PTR · 1 SOA · 4 TXT · 1 AAAA
WHOISchecked 2.4d ago
Details
Web4U s.r.o.
Registered 25 years ago
Expires Dec 16, 2026
Renewal history →
Then vs Nownew
No card for this name. We compare then and now for domains that are in the top million and had an AboutUs page. That says nothing about this domain’s age or safety.
Check what it is now →
SSL/TLSchecked 2.4d ago
Details
Valid certificate
Issuer: Let's Encrypt
Protocol: TLSv1.3
Expires in 22 days
2 SAN(s)
Securitychecked 2.4d ago
Details
B
190/225
1 high1 medium
Weakest: Basic Security, Advanced Security
Email Authchecked 2.4d ago
Details
SPFDKIMDMARC
Policy: reject
DNSSECchecked 2.4d ago
Details
Valid chain of trust
Tech Stackchecked 2.4d ago
Details
Web4U s.r.o.OpenRestyEmail: Self-hosted
HTTP / Headerschecked 2.4d ago
Details
2 redirect(s) → 200
HSTSCSPX-FrameNosniff
Threatschecked 2.4d ago
Details
Risk: none · score 0
Zone census
Subdomainschecked 2.4d ago
Details
10 found · 97 answered · 15 timed out (unknown)
imapmailmxmx2poppop3smtpwebmailwwwwww2
Click a subdomain for its full report
Web Archivechecked 2.4d ago
Details
First archived: 2001-02-21
~25 years of history
Deliverabilitychecked 2.4d ago
Details
96%A+
96/100 points · 2 issue(s)
1 MX · 2 IP(s)

IPv6

Measured 2026-11-15 15:46 UTC · aaaa.bot
A

Website, mail and DNS all work over IPv6.

The published IPv6 address accepted a connection when we tried it.

  • ✓ web4u.cz answers (1 of 1 addresses)
  • ✓ www.web4u.cz answers (1 of 1)
  • ✓ Mail: 1 of 1 servers have IPv6
  • ✓ Nameservers: 2 of 2 have IPv6
Details: published addresses and what answered

Loads over IPv6 with a valid certificate after 1 redirect: HTTP 200.

web4u.czPublished2001:1568::19Answers when we connect✓ answers on 443
www.web4u.czPublished2001:1568::19Answers when we connect✓ answers on 443
MailPublishedmx.web4u.czAnswers when we connect✓ has IPv6
NameserversPublishedns.web4u.czns2.web4u.czAnswers when we connect✓ has IPv6✓ has IPv6
First measured with IPv6 on 2026-11-04Changes are recorded from here on, each with its date.
Full check on aaaa.bot →Permanent receipt iUr64cOaVgJSON

See where it lives on the IPv4 map →

Lineage

Our records: Jan 2, 2009 → Nov 15, 2026

Oldest registry snapshot we hold: 2025 · 1 renewal on record. These dates are when our records begin, not when the domain was registered.

DNS provider

  • web4u.cz
    Jan 2009 – Jun 2026

IPv6

  • IPv6published, and answering
    First measured Nov 2026
What changed
  1. IPv6 first measured: published, and answering on Nov 4, 2026web4u.cz has 1 IPv6 address. Grade A. Measured by aaaa.bot, 2026-11-04 23:50 UTC. No earlier IPv6 record is held, so this is not a "gained" date.
  2. Renewed +1 year between Nov 8, 2025 and Nov 29, 2025Expiry moved from 2025-12-16 to 2026-12-16.

Solid bar: the stretch we observed that name. Dot: a single sighting. Dotted line: no record between sightings of the same name. Nothing is drawn between different names.

Registrar and renewals: 21 WHOIS/RDAP snapshots, 2025-01-12 to 2026-05-13 (ledger built 2026-09-27). Every renewal

DNS provider, WHOIS snapshots: 173 WHOIS/RDAP snapshots that listed nameservers, 2009-01-02 to 2026-06-15 (who.is archive). Both sources feed one row per provider (hover a bar to see which); a change is placed between the nearest observations on either side, and where the two sources disagree, both are listed under What changed.

Want to know when web4u.cz changes?

Monitor it free — 5 monitors, uptime checks every 5 minutes, email alerts when something breaks. No card required.

Monitor web4u.cz

Explore related

Registered in 2000 — the same year as twitter.com, yandex.net and wordpress.com.

AgeDomains from 2000TLD.cz domainsRegistrarWeb4U s.r.o.IPv6Does web4u.cz have IPv6?