Third-party-Tools to check your configuration


If you want to create a certificate, check your website or if you want to find hidden problems in your configuration: One of the following tools may be helpful. Some are small, some check a lot of things. Trouble to understand the results? Start a new topic in #help.

  1. Tools from active forum members:

1.1. Letsdebug - @_az

Checks a lot of things if the certificate creation doesn’t work. Option http/dns - checks. The main page is

with a Certificate Transparency search that removes duplicated pre/leaf-versions and some other features.

1.2 Unboundtest - Unbound DNS checker - @jsha

Use this server to make DNS queries against an Unbound instance and get logs. The Unbound instance is configured very similarly to Let’s Encrypt’s production servers, and is started fresh for each query so there are no caching effects.

1.3 Check your website - @JuergenAuer

Checks http / https / non-www / www to find wrong redirects and loops. Shows nameserver, ipv4 + ipv6, dnssec, certificates, incomplete chains, connection-settings, other dns-records (txt, CAA), mixed content, EDNS.

Check ipv4, ipv6, add a non-standard-port (5001, 8080 to check Synology- or Speedtest-configuration). Add a Hostname. So you can check a new ipv4/ipv6 address without having a DNS A- or AAAA-record.

Two Certificate Transparency monitors (CertSpotter + The list removes pre-certificates and shows a hitted limit. Subresource Integrity Check shows possible integrity hash values.

  1. Certificate Transparency Logs:


CRT / Comodo:

Use one of these search engines to find your certificates. Both are logging precertificates and leaf certificates. So creating one certificate -> two entries. Helpful if you don’t understand an Expiration mail (see ).

  1. Checking your DNS CAA configuration:

Use “Load Current Policy” to check if your CAA entry is correct. If your domain name is, check, and com.

  1. Checking your DNSSEC - configuration. - graphical output

  1. Tools to check your DNS - propagation - with ipv6-, curl- and other online-checks, Certificate-request-check - allows A, AAAA, TXT and CAA - check - mailserver, dns and other checks

  1. The Public Suffix List:

If you want to get a Letsencrypt certificate, your domain must end with a public suffix.

  1. If you want a certificate to secure your internal server, but you don’t have a domain name: There are some free domain provider.

Some of them have limitations. So if you have an important project, don’t use them.

You’ve got a new certificate. Now check your installation:

  1. Global SSL-configuration:

The main reference to check your SSL-configuration.

  1. The Mozilla website check - SSL and other parts

  1. Mozilla SSL Configuration Generator (Linux)

  1. IISCrypto (Windows 8 / 12 / 16)

  1. Check your mixed content warnings: FireFox or Chrome (Desktop), Then Ctrl + Shift + I, open the console. There the wrong links are listed.

  2. Online:

Has one limit: Doesn’t understand my own Letsencrypt EC-384 bit certificate. EC-256 works.

If you use cPanel, Plesk, Synology DiskStation Manager (DSM) or Pfsense: These tools have integrated solutions to create and install Letsencrypt certificates. So it’s the best idea to use these tools. Don’t mix them with command line tools.






If you want to use Cloudflare with https, you must have a valid certificate. Two options:

  • Use the integrated Cloudflare solution with a (not public trusted) internal Cloudflare Certificate to encrypt the traffic Your Server <–> Cloudflare. See
  • Create a Letsencrypt certificate, then activate Cloudflare. If you have Cloudflare activated or if your Letsencrypt certificate is expired -> deactivate Cloudflare or use dns-01 validation to create a new Letsencrypt certificate. You can’t use Cloudflare with an expired LE-certificate and http-01 validation.

Additional stuff:

  1. The Google HSTS Preload list

Requires Strict Transport Security header, domains are added to the Chrome Source code. Then browsers load the domain only via https.

  1. Static pages with configurations (no interactive online check):

  1. Certificate Transparency Search Engine with API:

  2. EDNS - Check:

Checks the correct answers if the DNS query contains EDNS-OPT records.

  1. DANE - Check and hash calculation

  1. Subresource Integrity hash calculation (hash check is included in my own tool)

Ideas, questions, other tools? Send a message or use the contact form of my profile link. Or use this topic:

Third-party-Tools to check your configuration - Discussion
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split this topic #2

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