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
CURL VariantsActionwww/non-www, trailing slash, HTTP→HTTPSREVIEW
www / non-www
Inconsistent — duplicate content risk
HTTP → HTTPS
Use 301 (permanent) instead of 302 (temporary)
BTLS Certificate Expiry & Recommendations253 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
A+DNS Records3 A records, 103 ms lookupPASS
| A | 3.210.78.247, 52.54.28.120, 3.224.232.42 |
| AAAA | — |
| CNAME | — |
| NS | ns-1020.awsdns-63.net, ns-1904.awsdns-46.co.uk, ns-247.awsdns-30.com, ns-1117.awsdns-11.org |
| MX | 10 aspmx.l.google.com 20 alt1.aspmx.l.google.com 20 alt2.aspmx.l.google.com 30 aspmx4.googlemail.com 30 aspmx3.googlemail.com 30 aspmx5.googlemail.com 30 aspmx2.googlemail.com |
| TXT | SPF v=spf1 ip4:100.25.59.11 ip4:205.201.128.0/20 ip4:198.2.128.0/18 ip4:148.105.8.0/... e622flctk14s3cs3ccdauh8uth jetbrains-domain-verification=bt8q7duih10l9pmf5fo5yy8wf klaviyo-site-verification=TGmZS7 stripe-verification=c8d270a115adc8c5a0a84fb24e17b7d05f66aad648d01e86f15548c6d025... amazonses:+SIz2NZPqYri3C+PSIyKShZIbuI4rNpbLlES7lmvpu4= _vg2bua41v8x489g1y55hg3hr4h3qmj0 slack-domain-verification=iuNWYimCCkEpnistAJvWc4YOZF8izoZ23TCDek0I google-site-verification=975UaH3lkKONB88HjWDDg34p8cdCqyTVSq_KGBAXrmU openai-domain-verification=dv-A4cFxdrYIEodfG6UiQU0qxnT openai-domain-verification=dv-ieCpefZUqvVQwb8f7o4SlFye spacelift-domain-verification=519xtPXm klaviyo-site-verification=RKdcF3 h1-domain-verification=sjPBeaGqQwEe8YhJ3W8JVNJa7WDQFAzc6AHkURoErkh324Yy pardot_208162_*=c15d5cb1b9f31e26058e1f30bda9e5d65c57cfeea37b34af8e1dd88474460e90 pardot_208162_*=610bfb45f202232a79db94c298b30d14332a62a6894e695b025fa7949d7b03fa docker-verification=b4ead4c5-fd66-42a5-a684-8f2e7f4c1417 apple-domain-verification=bMPI889zOgALUenN MS=ms66530579 aliyun-site-verification=1acfc148-50be-45c8-a021-3c933fc8eff9 anthropic-domain-verification-z4335b=YssTBALPY7K784Sri4FjVHjd3 rippling-domain-verification=9692f0635321f04d atlassian-sending-domain-verification=423a5faf-1cfa-4704-a38a-f7adae302dd6 |
| 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.
ARedirect Chain1 redirect(s), 865 ms totalPASS
https://duolingo.com
409 ms · HTTP/1.1
https://www.duolingo.com/
456 ms · HTTP/1.1 FINAL
| # | URL | Status | Time | Protocol | Server |
|---|---|---|---|---|---|
| 1 | https://duolingo.com | 302 | 409 ms | HTTP/1.1 | nginx/1.22.1 |
| 2 | https://www.duolingo.com/ | 200 | 456 ms | HTTP/1.1 | duo-api |
See the visual redirect chain in the HTTP Probe tab →
If permanent, use 301 instead.
302 (Found) is for genuinely temporary redirects — if this redirect is permanent, switch to 301 to preserve SEO equity.
Learn more ▾ ▴
Search engines treat 302 as temporary, keeping the original URL indexed and not transferring full link equity to the destination. Use 301 (Moved Permanently) for permanent redirects (HTTP→HTTPS, www-vs-non-www, URL restructures).
Source: Google Search Central
A+Crawlabilityrobots.txt present, sitemap with 4 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+Domain Intelligenceduolingo.com — via Amazon Registrar, Inc., 16 years, 5 months old, hosted on AWSPASS
225 days
January 26, 2027
253 days
Issued by Amazon
16 years, 5 months
Registered January 26, 2010
Not enabled
Protects against DNS spoofing
AWS
ASN AS14618
3.210.78.247
Amazon Registrar, Inc.
Expiry timeline
Recommended actions
- Enable DNSSEC to protect visitors from DNS spoofing
- Enable registrar lock (clientTransferProhibited) to block unauthorized domain transfers
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
The domain can be transferred without an unlock step. Enable registrar lock (clientTransferProhibited) in your registrar's control panel to protect against unauthorized or accidental transfers.
Without registrar lock, an attacker who phishes your registrar credentials can transfer the domain in minutes — total brand hijack.
Learn more ▾ ▴
Registrar lock (clientTransferProhibited, clientUpdateProhibited, clientDeleteProhibited) requires extra verification before any transfer/update/delete. Every major registrar offers it free. Combined with 2FA on your registrar account, it's the strongest defense against domain hijacking.
Source: ICANN / domain-security best practice