Infrastructure
· 9 checks — DNS, redirects, IPv6, crawlability, URL variants, and domain intelligence rolled into one auditable list.DCDN & DeliveryActionNo CDN detectedFIX
Consider using a CDN to improve global delivery speed and reduce origin load.
CIPv6 ReadinessActionNo IPv6 supportREVIEW
IPv6 support is increasingly important for global accessibility. About 40% of internet users have IPv6 connectivity.
No AAAA records — same impact as 'no IPv6 (AAAA) records'; IPv6-preferring clients pay extra latency falling back to IPv4.
Source: Google IPv6 stats
BTLS Certificate Expiry & Recommendations261 days until leaf cert expires — 4 issues to addressREVIEW
Certificate validity
Recommended actions
- Prefer TLS 1.3 — TLS 1.2 is acceptable but TLS 1.3 removes RSA key exchange and improves latency
- Enable HSTS: Strict-Transport-Security: max-age=31536000; includeSubDomains
- Enable DNSSEC on your domain for DNS spoofing protection
- Enable OCSP stapling on your TLS server to remove a CA roundtrip and protect user privacy
ADNS Records8 A records, 28 ms lookupPASS
| A | 54.84.143.251, 100.29.202.49, 3.219.15.9, 107.23.188.132, 23.20.46.217, 3.216.117.250, 34.203.20.106, 50.19.252.1 |
| AAAA | — |
| CNAME | — |
| NS | — |
| MX | — |
| TXT | — |
| CAA | Lookup not available with standard resolver |
CAA record lookup requires a specialized DNS resolver. This check will be available in a future update.
Informational: CAA (Certification Authority Authorization) records weren't checked in this scan.
SPF helps prevent email spoofing. Add a TXT record starting with 'v=spf1'.
Without SPF, receiving servers can't validate sending IPs — your domain is easier to spoof in phishing.
Learn more ▾ ▴
SPF complements DMARC. Both should be published. SPF records list authorized sending IPs (e.g., `v=spf1 include:_spf.google.com ~all` for Google Workspace). After publishing, verify in Google Postmaster Tools or mxtoolbox.
Source: RFC 7208 (SPF)
A+Redirect ChainNo redirects — direct accessPASS
https://www.duolingo.com
417 ms · HTTP/1.1 FINAL
| # | URL | Status | Time | Protocol | Server |
|---|---|---|---|---|---|
| 1 | https://www.duolingo.com | 200 | 417 ms | HTTP/1.1 | duo-api |
A+Crawlabilityrobots.txt present, sitemap with 5 URLsPASS
User-agent: *
Disallow: /sessions/
Disallow: /extend_session/
Disallow: /session_element_solutions/
Disallow: /friendships/
Disallow: /vocabularies/
Disallow: /diagnostics/
Disallow: /skills/
Disallow: /translations/
Disallow: /translation/
Disallow: /contribute/
Disallow: /documents/
Disallow: /matchmaker/
Disallow: /logger/
Disallow: /events/
Disallow: /facebook/
Disallow: /twitter/
Disallow: /words/
Disallow: /translate_jobs/
Disallow: /oauth/
Disallow: /data/
Disallow: /unsubscribe
Disallow: /deactivate
Disallow: /pm/
Disallow: /profile/
Disallow: /register/
Sitemap: https://www.duolingo.com/sitemap_index.xml
# Certain social media sites are added to allow crawlers to access page markup when links to /profile are shared.
User-agent: Twitterbot
Allow: /profile/
User-agent: facebookexternalhit
Allow: /profile/
A+URL Variantswww/non-www, trailing slash, HTTP→HTTPSPASS
www / non-www
Preferred variant: www
HTTP → HTTPS
Consistent
A+Domain Intelligenceduolingo.com — via Amazon Registrar, Inc., 16 years, 5 months old, hosted on AWSPASS
163 days
January 26, 2027
261 days
Issued by Amazon
16 years, 5 months
Registered January 26, 2010
Not enabled
Protects against DNS spoofing
AWS
ASN AS14618
32.194.155.93
Amazon Registrar, Inc.
Expiry timeline
Recommended actions
- Enable DNSSEC to protect visitors from DNS spoofing
DNSSEC protects against DNS spoofing attacks. While not required, enabling DNSSEC adds an additional layer of security. Contact your DNS provider to enable it.
Without DNSSEC, an attacker who can poison your DNS can hijack your domain — and SSL certs alone don't stop them.
Learn more ▾ ▴
DNSSEC adds cryptographic signatures to DNS records, preventing forged responses from poisoning resolver caches. Without it, an attacker who controls the network path can redirect your domain to a malicious server before any HTTPS handshake happens. Most modern registrars (Cloudflare, Google Domains, Route 53) enable it with one toggle.
Source: ICANN / RFC 4033