1. General Results, most used to calculate the result A name "2a01:238:301b::1226" is ipv6 address, public suffix is not defined A Good: All ip addresses are public addresses A Good: destination is https A Good: No cookie sent via http. A Good: every cookie sent via https is marked as secure A Good: Every cookie has a SameSite Attribute with a correct value Strict/Lax/None A Excellent: All cookies (except Cloudflare __cfduid) are Prefix-Cookies:4 Cookies complete, 4 __Host-Cookies, 0 __Secure-Cookies, 0 __cfduid-Cookies (Cloudflare) A Good: every https has a Strict Transport Security Header A Good: HSTS max-age is long enough, 63072000 seconds = 730 days A Good: HSTS has includeSubdomains - directive A Good: HSTS has preload directive Warning: HSTS preload sent, but not in Preload-List. Never send a preload directive if you don't know what preload means. Check https://hstspreload.org/ to learn the basics about the Google-Preload list. If you send a preload directive, you should **immediately** add your domain to the HSTS preload list via https://hstspreload.org/ . If Google accepts the domain, so the status is "pending": Note that new entries are hardcoded into the Chrome source code and can take several months before they reach the stable version. So you will see this message some months. If you don't want that or if you don't understand "preload", but if you send a preload directive and if you have correct A-redirects, everybody can add your domain to that list. Then you may have problems, it's not easy to undo that. So if you don't want your domain preloaded, remove the preload directive. A Good: All urls with http status 200/404 have a complete Content-Type header (MediaType / MediaSubType + correct charset) N https://[2a01:0238:301b:0000:0000:0000:0000:1226]/ 2a01:238:301b::1226 Error - Certificate isn't trusted, RemoteCertificateNameMismatch 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.2a01:238:301b::1226 2. Header-Checks A www.server-daten.de Content-Security-Policy Ok: Header without syntax errors found: default-src 'none'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; script-src 'self'; connect-src 'self'; child-src 'self'; frame-src 'self'; frame-ancestors 'self'; form-action 'self'; base-uri 'self'; report-uri /-cspr.html; report-to default B Info: Header-Element is deprecated. report-uri /-cspr.html A Good: default-src directive only with 'none' or 'self', additional sources are blocked. A Good: default-src without 'unsafe-inline' or 'unsave-eval'. A Good: report-to label defined, report-to - header defined and the label is a member. default A Good: form-action directive found. That reduces the risk sending data to unwanted domains. form-action is a navigation-directive, so default-src isn't used. A Good: frame-ancestors directive found. That limits pages who are allowed to use this page in a frame / iframe / object / embed / applet. frame-ancestors is a navigation-directive, so default-src isn't used. A Good: base-uri directive found. That limits the URLs which can be used in a document's <base> element. Because it's a document directive, default-src isn't used, so an own directive is required. A Good: No object-src found, but the default-src used as fallback is defined and restricted. A Good: script-src without 'unsafe-inline' and 'unsafe-eval' found. That's the recommended configuration. A Good: script-src without * and a scheme found. A Good: script-src without data: schema found. Why is this important? The data: schema allows hidden code injection. Insert <script src='data:application/javascript;base64,YWxlcnQoJ1hTUycpOw=='></script> in your page and see what happens. A Good: frame-src without data: defined or frame-src missing and the default-src used as fallback not allows the data: schema. That blocks hidden code injection. Insert <iframe src="data:text/html;charset=utf-8;base64,PCFET0NUWVBFIGh0bWw+PGh0bWw+PGJvZHk+PHA+YmVmb3JlPHNjcmlwdCB0eXBlPSJ0ZXh0L2phdmFzY3JpcHQiPmFsZXJ0KCdYU1MnKTwvc2NyaXB0PjxwPmFmdGVyPC9ib2R5PjwvaHRtbD4="></iframe> in your page and see what happens. A report-to Ok: Header without syntax errors found: {"group":"default","max_age":3600,"endpoints":[{"url":"https://www.server-daten.de/-cspr.html"}],"include_subdomains":false} A Ok: Header without syntax errors found: {"group":"default","max_age":3600,"endpoints":[{"url":"https://www.server-daten.de/-cspr.html"}],"include_subdomains":false} A X-Content-Type-Options Ok: Header without syntax errors found: nosniff A Referrer-Policy Ok: Header without syntax errors found: strict-origin A Permissions-Policy Ok: Header without syntax errors found: camera=(self) A X-Frame-Options Ok: Header without syntax errors found: SAMEORIGIN B Info: Header is deprecated. May not longer work in modern browsers. SAMEORIGIN. Better solution: Use a Content-Security-Policy Header with a frame-ancestors directive. DENY - use 'none', SAMEORIGIN - use 'self'. If you want to allow some domains to frame your page, add these urls. A X-Xss-Protection Ok: Header without syntax errors found: 1; mode=block B Info: Header is deprecated. May not longer work in modern browsers. 1; mode=block A www.server-daten.de 2a01:238:301b::1226 Content-Security-Policy Ok: Header without syntax errors found: default-src 'none'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; script-src 'self'; connect-src 'self'; child-src 'self'; frame-src 'self'; frame-ancestors 'self'; form-action 'self'; base-uri 'self'; report-uri /-cspr.html; report-to default B Info: Header-Element is deprecated. report-uri /-cspr.html A Good: default-src directive only with 'none' or 'self', additional sources are blocked. A Good: default-src without 'unsafe-inline' or 'unsave-eval'. A Good: report-to label defined, report-to - header defined and the label is a member. default A Good: form-action directive found. That reduces the risk sending data to unwanted domains. form-action is a navigation-directive, so default-src isn't used. A Good: frame-ancestors directive found. That limits pages who are allowed to use this page in a frame / iframe / object / embed / applet. frame-ancestors is a navigation-directive, so default-src isn't used. A Good: base-uri directive found. That limits the URLs which can be used in a document's <base> element. Because it's a document directive, default-src isn't used, so an own directive is required. A Good: No object-src found, but the default-src used as fallback is defined and restricted. A Good: script-src without 'unsafe-inline' and 'unsafe-eval' found. That's the recommended configuration. A Good: script-src without * and a scheme found. A Good: script-src without data: schema found. Why is this important? The data: schema allows hidden code injection. Insert <script src='data:application/javascript;base64,YWxlcnQoJ1hTUycpOw=='></script> in your page and see what happens. A Good: frame-src without data: defined or frame-src missing and the default-src used as fallback not allows the data: schema. That blocks hidden code injection. Insert <iframe src="data:text/html;charset=utf-8;base64,PCFET0NUWVBFIGh0bWw+PGh0bWw+PGJvZHk+PHA+YmVmb3JlPHNjcmlwdCB0eXBlPSJ0ZXh0L2phdmFzY3JpcHQiPmFsZXJ0KCdYU1MnKTwvc2NyaXB0PjxwPmFmdGVyPC9ib2R5PjwvaHRtbD4="></iframe> in your page and see what happens. A report-to Ok: Header without syntax errors found: {"group":"default","max_age":3600,"endpoints":[{"url":"https://www.server-daten.de/-cspr.html"}],"include_subdomains":false} A Ok: Header without syntax errors found: {"group":"default","max_age":3600,"endpoints":[{"url":"https://www.server-daten.de/-cspr.html"}],"include_subdomains":false} A X-Content-Type-Options Ok: Header without syntax errors found: nosniff A Referrer-Policy Ok: Header without syntax errors found: strict-origin A Permissions-Policy Ok: Header without syntax errors found: camera=(self) A X-Frame-Options Ok: Header without syntax errors found: SAMEORIGIN B Info: Header is deprecated. May not longer work in modern browsers. SAMEORIGIN. Better solution: Use a Content-Security-Policy Header with a frame-ancestors directive. DENY - use 'none', SAMEORIGIN - use 'self'. If you want to allow some domains to frame your page, add these urls. A X-Xss-Protection Ok: Header without syntax errors found: 1; mode=block B Info: Header is deprecated. May not longer work in modern browsers. 1; mode=block 3. DNS- and NameServer - Checks 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. A Good: Every https result with status 200 has a minified Html-Content with a quota lower then 110 %. A Good: Every https connection via port 443 supports the http/2 protocol via ALPN. A Info: No img element found, no alt attribute checked A Duration: 50220 milliseconds, 50.220 seconds