1. General Results, most used to calculate the result A name "timonoj.duckdns.org" is domain, public suffix is ".duckdns.org", top-level-domain is ".org", top-level-domain-type is "generic", tld-manager is "Public Interest Registry (PIR)", num .org-domains preloaded: 7098 (complete: 210599) A Good: All ip addresses are public addresses Warning: Only one ip address found: timonoj.duckdns.org has only one ip address. Warning: No ipv6 address found. Ipv6 is the future with a lot of new features. So every domain name should have an ipv6 address. See https://en.wikipedia.org/wiki/IPv6: timonoj.duckdns.org has no ipv6 address. A https://timonoj.duckdns.org/ 221.124.47.85 https://timonoj.duckdns.org/accounts/login/?next=/ Correct redirect https to https A https://www.timonoj.duckdns.org/ 221.124.47.85 https://www.timonoj.duckdns.org/accounts/login/?next=/ Correct redirect https to https A https://221.124.47.85/ 221.124.47.85 https://timonoj.duckdns.org/accounts/login/?next=/ Correct redirect https to https A Good: destination is https A Good: No cookie sent via http. A Good: Every cookie has a SameSite Attribute with a correct value Strict/Lax/None HSTS-Preload-Status: unknown. Domain never included in the Preload-list. Check https://hstspreload.org/ to learn some basics about the Google-Preload-List. A Good: Some urls with http status 200/404 have a complete Content-Type header (MediaType / MediaSubType + correct charset):2 complete Content-Type - header (4 urls) https://timonoj.duckdns.org/.well-known/acme-challenge/check-your-website-dot-server-daten-dot-de Url with incomplete Content-Type - header - missing charset https://www.timonoj.duckdns.org/.well-known/acme-challenge/check-your-website-dot-server-daten-dot-de Url with incomplete Content-Type - header - missing charset A http://timonoj.duckdns.org/ 221.124.47.85 https://timonoj.duckdns.org/ Correct redirect http - https with the same domain name A http://www.timonoj.duckdns.org/ 221.124.47.85 https://www.timonoj.duckdns.org/ Correct redirect http - https with the same domain name B https://timonoj.duckdns.org/.well-known/acme-challenge/check-your-website-dot-server-daten-dot-de Missing HSTS-Header B https://www.timonoj.duckdns.org/.well-known/acme-challenge/check-your-website-dot-server-daten-dot-de Missing HSTS-Header B https://timonoj.duckdns.org/accounts/login/?next=/ sfcsrftoken=sxTobo3Z29PtRYBjcqkKEGTw5zYZlyTWrzqLVsuerOWe6dY6MHiUB12fy2T9TwCD; expires=Mon, 13 Nov 2023 06:34:46 GMT; Max-Age=31449600; Path=/; SameSite=Lax Cookie sent via https, but not marked as secure B https://timonoj.duckdns.org/accounts/login/?next=/ sessionid=xfl0pj2gd10k38v26pq8zp4mp7inam1w; expires=Tue, 15 Nov 2022 06:34:46 GMT; HttpOnly; Max-Age=86400; Path=/; SameSite=Lax Cookie sent via https, but not marked as secure B https://www.timonoj.duckdns.org/accounts/login/?next=/ sfcsrftoken=jTOwaXodHbCRbkHiT07Da7ktDso3QHYCCz8UcwK2LpynaQ8wQdlaazxlKaMWws4A; expires=Mon, 13 Nov 2023 06:34:54 GMT; Max-Age=31449600; Path=/; SameSite=Lax Cookie sent via https, but not marked as secure B https://www.timonoj.duckdns.org/accounts/login/?next=/ sessionid=jpt23c8pzlb47i2jh6k7l3todwvxv833; expires=Tue, 15 Nov 2022 06:34:54 GMT; HttpOnly; Max-Age=86400; Path=/; SameSite=Lax Cookie sent via https, but not marked as secure C Error - no preferred version www or non-www. Select one version as preferred version, then add a redirect https + not-preferred version to https + preferred version. Perhaps in your port 443 vHost something like "RewriteEngine on" + "RewriteCond %{SERVER_NAME} = example.com" + "ReWriteRule ^ https://www.example.com%{REQUEST_URI} [END,QSA,R=permanent]" (three rows, without the "). That should create a redirect https + example.com ⇒ https + www.example.com. Or switch both values to use the non-www version as your preferred version. C Error - more then one version with Http-Status 200. After all redirects, all users (and search engines) should see the same https url: Non-www or www, but not both with http status 200. I https://timonoj.duckdns.org/accounts/login/?next=/ Content problems or problems with resources included - http links, files doesn't exist, different Content-Type definitions. Check the Html-Content - Part. I https://www.timonoj.duckdns.org/accounts/login/?next=/ Content problems or problems with resources included - http links, files doesn't exist, different Content-Type definitions. Check the Html-Content - Part. N https://www.timonoj.duckdns.org/ 221.124.47.85 https://www.timonoj.duckdns.org/accounts/login/?next=/ Error - Certificate isn't trusted, RemoteCertificateNameMismatch N https://www.timonoj.duckdns.org/accounts/login/?next=/ Error - Certificate isn't trusted, RemoteCertificateNameMismatch N https://www.timonoj.duckdns.org/.well-known/acme-challenge/check-your-website-dot-server-daten-dot-de Error - Certificate isn't trusted, RemoteCertificateNameMismatch N https://221.124.47.85/ 221.124.47.85 https://timonoj.duckdns.org/accounts/login/?next=/ Error - Certificate isn't trusted, RemoteCertificateNameMismatch O timonoj.duckdns.org / 221.124.47.85 / 443 Old connection: Cipher Suites without Forward Secrecy (FS) found. Remove all of these Cipher Suites, use only Cipher Suites with Forward Secrecy: Starting with ECDHE- or DHE - the last "E" says: "ephemeral". Or use Tls.1.3, then all Cipher Suites use FS. 16 Cipher Suites without Forward Secrecy found X Fatal error: Nameserver doesn't support TCP connection: ns1.duckdns.org: Timeout X Fatal error: Nameserver doesn't support TCP connection: ns1.duckdns.org / 99.79.143.35: Timeout X Fatal error: Nameserver doesn't support TCP connection: ns2.duckdns.org: Timeout X Fatal error: Nameserver doesn't support TCP connection: ns2.duckdns.org / 35.182.183.211: Timeout X Fatal error: Nameserver doesn't support TCP connection: ns3.duckdns.org: Timeout X Fatal error: Nameserver doesn't support TCP connection: ns3.duckdns.org / 35.183.157.249: Timeout X Fatal error: Nameserver doesn't support TCP connection: ns4.duckdns.org: Timeout X Fatal error: Nameserver doesn't support TCP connection: ns4.duckdns.org / 3.97.51.116: Timeout X Fatal error: Nameserver doesn't support TCP connection: ns5.duckdns.org: Timeout X Fatal error: Nameserver doesn't support TCP connection: ns5.duckdns.org / 99.79.16.64: Timeout X Fatal error: Nameserver doesn't support TCP connection: ns6.duckdns.org: Timeout X Fatal error: Nameserver doesn't support TCP connection: ns6.duckdns.org / 3.97.58.28: Timeout Info: Checking all ip addresses of that domain without sending the hostname only one certificate found. Checking all ip addresses and sending the hostname only one certificate found. Both certificates are the same. So that domain doesn't require Server Name Indication (SNI), it's the primary certificate of that set of ip addresses.: Domain timonoj.duckdns.org, 1 ip addresses, 1 different http results. B No _mta-sts TXT record found (mta-sts: Mail Transfer Agent Strict Transport Security - see RFC 8461). Read the result of server-daten.de (Url-Checks, Comments, Connections and DomainServiceRecords) to see a complete definition. Domainname: _mta-sts.timonoj.duckdns.org 2. Header-Checks (alpha, started 2022-10-23, may be buggy / incomplete) F timonoj.duckdns.org Content-Security-Policy Critical: Missing Header: F timonoj.duckdns.org X-Content-Type-Options Critical: Missing Header: F timonoj.duckdns.org Referrer-Policy Critical: Missing Header: F timonoj.duckdns.org Permissions-Policy Critical: Missing Header: F www.timonoj.duckdns.org Content-Security-Policy Critical: Missing Header: F www.timonoj.duckdns.org X-Content-Type-Options Critical: Missing Header: F www.timonoj.duckdns.org Referrer-Policy Critical: Missing Header: F www.timonoj.duckdns.org Permissions-Policy Critical: Missing Header: 3. DNS- and NameServer - Checks A Info:: 2 Root-climbing DNS Queries required to find all IPv4- and IPv6-Addresses of 6 Name Servers. A Info:: 2 Queries complete, 2 with IPv6, 0 with IPv4. A Good: All DNS Queries done via IPv6. A Good: Some ip addresses of name servers found with the minimum of two DNS Queries. One to find the TLD-Zone, one to ask the TLD-Zone.ns1.duckdns.org (99.79.143.35), ns2.duckdns.org (35.182.183.211), ns3.duckdns.org (35.183.157.249), ns4.duckdns.org (3.97.51.116), ns5.duckdns.org (99.79.16.64), ns6.duckdns.org (3.97.58.28) A Good (1 - 3.0):: An average of 0.3 queries per domain name server required to find all ip addresses of all name servers. A Info:: 6 different Name Servers found: ns1.duckdns.org, ns2.duckdns.org, ns3.duckdns.org, ns4.duckdns.org, ns5.duckdns.org, ns6.duckdns.org, 6 Name Servers included in Delegation: ns1.duckdns.org, ns2.duckdns.org, ns3.duckdns.org, ns4.duckdns.org, ns5.duckdns.org, ns6.duckdns.org, 6 Name Servers included in 1 Zone definitions: ns1.duckdns.org, ns2.duckdns.org, ns3.duckdns.org, ns4.duckdns.org, ns5.duckdns.org, ns6.duckdns.org, 1 Name Servers listed in SOA.Primary: ns1.duckdns.org. A Good: Only one SOA.Primary Name Server found.: ns1.duckdns.org. A Good: SOA.Primary Name Server included in the delegation set.: ns1.duckdns.org. A Good: Consistency between delegation and zone. The set of NS records served by the authoritative name servers must match those proposed for the delegation in the parent zone. Ordered list of name servers: ns1.duckdns.org, ns2.duckdns.org, ns3.duckdns.org, ns4.duckdns.org, ns5.duckdns.org, ns6.duckdns.org A Good: All Name Server Domain Names have a Public Suffix. A Good: All Name Server Domain Names ending with a Public Suffix have minimal one IPv4- or IPv6 address. A Good: All Name Server ip addresses are public. A Good: Minimal 2 different name servers (public suffix and public ip address) found: 6 different Name Servers found Warning: No Name Server IPv6 address found. IPv6 is the future, so your name servers should be visible via IPv6.: 6 different Name Servers found Warning: All Name Servers have the same Top Level Domain / Public Suffix. If there is a problem with that Top Level Domain, your domain may be affected. Better: Use Name Servers with different top level domains.: 6 Name Servers, 1 Top Level Domain: duckdns.org Warning: All Name Servers have the same domain name. If there is a problem with that domain name (or with the name servers of that domain name), your domain may be affected. Better: Use Name Servers with different domain names / different top level domains.: Only one domain name used: Warning: All Name Servers from the same Country / IP location.: 6 Name Servers, 1 Countries: CA A Info: Ipv4-Subnet-list: 6 Name Servers, 3 different subnets (first Byte): 3., 35., 99., 4 different subnets (first two Bytes): 3.97., 35.182., 35.183., 99.79., 6 different subnets (first three Bytes): 3.97.51., 3.97.58., 35.182.183., 35.183.157., 99.79.143., 99.79.16. A Good: Name Server IPv4-addresses from different subnet found: A Good: Nameserver supports Echo Capitalization: 6 good Nameserver X Nameserver Timeout checking Echo Capitalization: ns5.duckdns.org A Good: Nameserver supports EDNS with max. 512 Byte Udp payload, message is smaller: 6 good Nameserver Nameserver doesn't pass all EDNS-Checks: ns1.duckdns.org: OP100: ok. FLAGS: ok. V1: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. V1OP100: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found, no OPT100 expected, no OPT100 found. V1FLAGS: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. DNSSEC: ok. V1DNSSEC: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. NSID: ok. COOKIE: ok. CLIENTSUBNET: ok. Nameserver doesn't pass all EDNS-Checks: ns1.duckdns.org / 99.79.143.35: OP100: ok. FLAGS: ok. V1: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. V1OP100: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found, no OPT100 expected, no OPT100 found. V1FLAGS: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. DNSSEC: ok. V1DNSSEC: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. NSID: ok. COOKIE: ok. CLIENTSUBNET: ok. Nameserver doesn't pass all EDNS-Checks: ns1.duckdns.org / 99.79.143.35: OP100: ok. FLAGS: ok. V1: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. V1OP100: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found, no OPT100 expected, no OPT100 found. V1FLAGS: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. DNSSEC: ok. V1DNSSEC: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. NSID: ok. COOKIE: ok. CLIENTSUBNET: ok. Nameserver doesn't pass all EDNS-Checks: ns2.duckdns.org: OP100: ok. FLAGS: ok. V1: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. V1OP100: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found, no OPT100 expected, no OPT100 found. V1FLAGS: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. DNSSEC: ok. V1DNSSEC: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. NSID: ok. COOKIE: ok. CLIENTSUBNET: ok. Nameserver doesn't pass all EDNS-Checks: ns2.duckdns.org / 35.182.183.211: OP100: ok. FLAGS: ok. V1: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. V1OP100: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found, no OPT100 expected, no OPT100 found. V1FLAGS: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. DNSSEC: ok. V1DNSSEC: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. NSID: ok. COOKIE: ok. CLIENTSUBNET: ok. Nameserver doesn't pass all EDNS-Checks: ns2.duckdns.org / 35.182.183.211: OP100: ok. FLAGS: ok. V1: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. V1OP100: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found, no OPT100 expected, no OPT100 found. V1FLAGS: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. DNSSEC: ok. V1DNSSEC: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. NSID: ok. COOKIE: ok. CLIENTSUBNET: ok. Nameserver doesn't pass all EDNS-Checks: ns3.duckdns.org: OP100: ok. FLAGS: ok. V1: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. V1OP100: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found, no OPT100 expected, no OPT100 found. V1FLAGS: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. DNSSEC: ok. V1DNSSEC: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. NSID: ok. COOKIE: ok. CLIENTSUBNET: ok. Nameserver doesn't pass all EDNS-Checks: ns3.duckdns.org / 35.183.157.249: OP100: ok. FLAGS: ok. V1: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. V1OP100: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found, no OPT100 expected, no OPT100 found. V1FLAGS: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. DNSSEC: ok. V1DNSSEC: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. NSID: ok. COOKIE: ok. CLIENTSUBNET: ok. Nameserver doesn't pass all EDNS-Checks: ns3.duckdns.org / 35.183.157.249: OP100: ok. FLAGS: ok. V1: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. V1OP100: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found, no OPT100 expected, no OPT100 found. V1FLAGS: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. DNSSEC: ok. V1DNSSEC: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. NSID: ok. COOKIE: ok. CLIENTSUBNET: ok. Nameserver doesn't pass all EDNS-Checks: ns4.duckdns.org: OP100: ok. FLAGS: ok. V1: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. V1OP100: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found, no OPT100 expected, no OPT100 found. V1FLAGS: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. DNSSEC: ok. V1DNSSEC: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. NSID: ok. COOKIE: ok. CLIENTSUBNET: ok. Nameserver doesn't pass all EDNS-Checks: ns4.duckdns.org / 3.97.51.116: OP100: ok. FLAGS: ok. V1: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. V1OP100: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found, no OPT100 expected, no OPT100 found. V1FLAGS: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. DNSSEC: ok. V1DNSSEC: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. NSID: ok. COOKIE: ok. CLIENTSUBNET: ok. Nameserver doesn't pass all EDNS-Checks: ns4.duckdns.org / 3.97.51.116: OP100: ok. FLAGS: ok. V1: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. V1OP100: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found, no OPT100 expected, no OPT100 found. V1FLAGS: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. DNSSEC: ok. V1DNSSEC: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. NSID: ok. COOKIE: ok. CLIENTSUBNET: ok. Nameserver doesn't pass all EDNS-Checks: ns5.duckdns.org: OP100: ok. FLAGS: ok. V1: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. V1OP100: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found, no OPT100 expected, no OPT100 found. V1FLAGS: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. DNSSEC: ok. V1DNSSEC: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. NSID: ok. COOKIE: ok. CLIENTSUBNET: ok. Nameserver doesn't pass all EDNS-Checks: ns5.duckdns.org / 99.79.16.64: OP100: ok. FLAGS: ok. V1: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. V1OP100: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found, no OPT100 expected, no OPT100 found. V1FLAGS: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. DNSSEC: ok. V1DNSSEC: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. NSID: ok. COOKIE: ok. CLIENTSUBNET: ok. Nameserver doesn't pass all EDNS-Checks: ns5.duckdns.org / 99.79.16.64: OP100: ok. FLAGS: ok. V1: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. V1OP100: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found, no OPT100 expected, no OPT100 found. V1FLAGS: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. DNSSEC: ok. V1DNSSEC: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. NSID: ok. COOKIE: ok. CLIENTSUBNET: ok. Nameserver doesn't pass all EDNS-Checks: ns6.duckdns.org: OP100: fatal timeout. FLAGS: fatal timeout. V1: fatal timeout. V1OP100: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found, no OPT100 expected, no OPT100 found. V1FLAGS: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. DNSSEC: fatal timeout. V1DNSSEC: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. NSID: fatal timeout. COOKIE: fatal timeout. CLIENTSUBNET: fatal timeout. Nameserver doesn't pass all EDNS-Checks: ns6.duckdns.org / 3.97.58.28: OP100: ok. FLAGS: ok. V1: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. V1OP100: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found, no OPT100 expected, no OPT100 found. V1FLAGS: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. DNSSEC: ok. V1DNSSEC: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. NSID: ok. COOKIE: ok. CLIENTSUBNET: ok. Nameserver doesn't pass all EDNS-Checks: ns6.duckdns.org / 3.97.58.28: OP100: ok. FLAGS: ok. V1: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. V1OP100: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found, no OPT100 expected, no OPT100 found. V1FLAGS: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. DNSSEC: ok. V1DNSSEC: SOA NOT expected, but found, BADVER expected, NOERR found, Version 0 expectend and found. NSID: ok. COOKIE: ok. CLIENTSUBNET: ok. A Good: All SOA have the same Serial Number Warning: No CAA entry with issue/issuewild found, every CAA can create a certificate. Read https://en.wikipedia.org/wiki/DNS_Certification_Authority_Authorization to learn some basics about the idea of CAA. Your name server must support such an entry. Not all dns providers support CAA entries. 4. Content- and Performance-critical Checks A Good: All checks /.well-known/acme-challenge/random-filename without redirects answer with the expected http status 404 - Not Found. Creating a Letsencrypt certificate via http-01 challenge should work. If it doesn't work: Check your vHost configuration (apachectl -S, httpd -S, nginx -T). Every combination of port and ServerName / ServerAlias (Apache) or Server (Nginx) must be unique. Merge duplicated entries in one vHost. If you use an IIS, extensionless files must be allowed in the /.well-known/acme-challenge subdirectory. Create a web.config in that directory. Content: <configuration><system.webServer><staticContent><mimeMap fileExtension="." mimeType="text/plain" /></staticContent></system.webServer></configuration>. If you have a redirect http ⇒ https, that's ok, Letsencrypt follows such redirects to port 80 / 443 (same or other server). There must be a certificate. But the certificate may be expired, self signed or with a not matching domain name. Checking the validation file Letsencrypt ignores such certificate errors. Trouble creating a certificate? Use https://community.letsencrypt.org/ to ask. A Good: Every https result with status 200 supports GZip. https://timonoj.duckdns.org/accounts/login/?next=/ Warning: Https + http status 200 + Inline CSS / JavaScript found. Don't use inline CSS / JavaScript. These are compiled and re-used ressources, save these with a long Cache-Control max-age - header. https://www.timonoj.duckdns.org/accounts/login/?next=/ Warning: Https + http status 200 + Inline CSS / JavaScript found. Don't use inline CSS / JavaScript. These are compiled and re-used ressources, save these with a long Cache-Control max-age - header. https://timonoj.duckdns.org/accounts/login/?next=/ Warning: Https result with status 200 found, Html-Content is too big. Should be max. 110 %. May contain inline CSS / JavaScript, too much comments or white space. Re-used ressources - create files with a long Cache-Control max-age header. Remove comments and white space. https://www.timonoj.duckdns.org/accounts/login/?next=/ Warning: Https result with status 200 found, Html-Content is too big. Should be max. 110 %. May contain inline CSS / JavaScript, too much comments or white space. Re-used ressources - create files with a long Cache-Control max-age header. Remove comments and white space. https://timonoj.duckdns.org/accounts/login/?next=/ Warning: Https connections (Standard Port 443) found without support of the http/2 protocol via ALPN. Http/2 is the new Http-Version (old: http 1.1) with some important new features. Update your server software so http/2 is available. Only one TCP-connection per Server (that's a performance boost), Header-Compression and Server Pushs are available. Domain Sharding and Inline-CSS/Javascript shouldn't used with http/2. https://www.timonoj.duckdns.org/accounts/login/?next=/ Warning: Https connections (Standard Port 443) found without support of the http/2 protocol via ALPN. Http/2 is the new Http-Version (old: http 1.1) with some important new features. Update your server software so http/2 is available. Only one TCP-connection per Server (that's a performance boost), Header-Compression and Server Pushs are available. Domain Sharding and Inline-CSS/Javascript shouldn't used with http/2. https://timonoj.duckdns.org/accounts/login/?next=/ Critical: Some script Elements (type text/javascript) with a src-Attribute don't have a defer / async - Attribute. Loading and executing these JavaScripts blocks parsing and rendering the Html-Output. That's bad if your site is large or the connection is slow / mobile usage. Use "async" if the js file has only functions (so nothing is executed after parsing the file) or is independend. Use "defer" if the order of the scripts is important. All "defer" scripts are executed before the DOMContentLoaded event is fired. Check https://developer.mozilla.org/en-US/docs/Web/HTML/Element/script to see some details.: 4 script elements without defer/async. https://www.timonoj.duckdns.org/accounts/login/?next=/ Critical: Some script Elements (type text/javascript) with a src-Attribute don't have a defer / async - Attribute. Loading and executing these JavaScripts blocks parsing and rendering the Html-Output. That's bad if your site is large or the connection is slow / mobile usage. Use "async" if the js file has only functions (so nothing is executed after parsing the file) or is independend. Use "defer" if the order of the scripts is important. All "defer" scripts are executed before the DOMContentLoaded event is fired. Check https://developer.mozilla.org/en-US/docs/Web/HTML/Element/script to see some details.: 4 script elements without defer/async. Warning: CSS / JavaScript found without GZip support. Send these ressources with GZip. 14 external CSS / JavaScript files without GZip found - 0 with GZip, 14 complete A Good: All images with internal compression not sent via GZip. Images (.png, .jpg) are already compressed, so an additional GZip isn't helpful. 2 images (type image/png, image/jpg) found without additional GZip. Not required because these images are already compressed Warning: CSS / JavaScript files with a missing or too short Cache-Control header found. Browsers should cache and re-use these files. 14 external CSS / JavaScript files without Cache-Control-Header, 0 with Cache-Control, but no max-age, 0 with Cache-Control max-age too short (minimum 7 days), 0 with Cache-Control long enough, 14 complete. Warning: Images with a missing or too short Cache-Control header found. Browsers should cache and re-use these files. 2 image files without Cache-Control-Header, 0 with Cache-Control, but no max-age, 0 with Cache-Control max-age too short (minimum 7 days), 0 with Cache-Control long enough, 2 complete. A Good: All checked attribute values are enclosed in quotation marks (" or '). A Good: All img-elements have a valid alt-attribute.: 2 img-elements found. A Good: Domainname is not on the "Specially Designated Nationals And Blocked Persons List" (SDN). That's an US-list of individuals and companies owned or controlled by, or acting for or on behalf of, targeted countries. It also lists individuals, groups, and entities, such as terrorists and narcotics traffickers designated under programs that are not country-specific. Collectively, such individuals and companies are called "Specially Designated Nationals" or "SDNs." Their assets are blocked and U.S. persons are generally prohibited from dealing with them. So if a domain name is on that list, it's impossible to create a Letsencrypt certificate with that domain name. Check the list manual - https://www.treasury.gov/resource-center/sanctions/sdn-list/pages/default.aspx https://timonoj.duckdns.org/.well-known/acme-challenge/check-your-website-dot-server-daten-dot-de 5.800 seconds Warning: 404 needs more then one second https://www.timonoj.duckdns.org/.well-known/acme-challenge/check-your-website-dot-server-daten-dot-de 5.937 seconds Warning: 404 needs more then one second A Duration: 1716534 milliseconds, 1716.534 seconds