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Local HTTPS for Optimizely, IIS, and Kestrel using certificates (Pt 1)

Cyber security firewall interface protection concept HTTPS certificates. Businesswoman protecting herself from cyber attacks. Personal data security and banking. stock photo

Wasn’t it around 2006 when HTTPS started becoming popular? You’d go to a secure page and almost always see a message saying, “This page contains both secure and nonsecure items. Do you want to display the insecure items?” 1

Display Nonsecure Items

“Helpful” people online posted how to disable the error. Then browsers got smarter and just stopped delivering the non-secure mixed content altogether, relinquishing the error message to the console. 1

Why this trip down memory lane? Because it’s 2023 and some of us are still developing solutions in an unsecure HTTP environment!

One of the easiest ways to minimize UAT/production bugs is to make your development environment as close to identical to the UAT/production environment as possible (and feasible). Let’s start by making your local environment HTTPS-only.

Creating a Self-Signed SSL Certificate

Working on a local machine, we don’t want to spend the money or time going through the process of registering an SSL certificate with the ICANN lookup. They can’t verify https://localhost/mysite anyway. Luckily, we don’t need to. We can use a Self-Signed Certificate, or a Client-side Certificate.

Note: These instructions are for Windows-based computers

Certificate without password

  1. Update the following command with the name of your domain (we’re using “mydomain.local” as an example).
  2. Open a Powershell window with Admin rights and paste the updated command.2
    New-SelfSignedCertificate -Subject "mydomain.local" -DnsName mydomain.local, *.mydomain.local -CertStoreLocation Cert:\LocalMachine\My -NotAfter (Get-Date).AddYears(10)

What do the switches do?

  • -Subject: This will create a friendly name to reference the certificate when browsing the store.
  • -DnsName: This is a key piece of information the system uses to associate a URL/domain with your certificate. Note that there are two entries: an explicit domain and a wildcard domain. The additional wildcard domain will allow you to build subdomains off the main domain without needing a new certificate.
  • -CertStoreLocation: This is where the certificate is stored on your machine.
  • -NotAfter (optional): This sets the certificate’s expiration date. In this case, we’re setting it for 10 years out.

We can use the certificate in a couple of ways:

Assign it to the Trusted Store

  1. At a Windows Run screen (Win + R), type “certlm.msc”. This will open the Local Machine’s Certificate Store.
  2. Open “Personal” > “Certificates”
  3. Find the certificate you just created.
  4. Copy it (Right click + Copy) and paste it inside the “Trusted Root Certification Authorities” > “Certificates” folder (Right click + Paste)

Export it as a file to be imported when needed

  1. At a Windows Run screen (Win + R), type “certlm.msc”. This will open the Local Machine’s Certificate Store.
  2. Open “Personal” > “Certificates”
  3. Find the certificate you just created.
  4. Right-click, choose “All Tasks” > “Export”.
    1. The first screen explains the certificate export process.
    2. Select all of the default values on the next two screens.
    3. Browse to where you want to save the .CER file and type in the name where asked.
    4. Verify the options selected and click “Finish” to create your certificate.
  5. To import the certificate, right-click on the folder and choose “All Tasks” > “Import”. Follow the prompts.

Certificate with password (using PowerShell 5+) 3

Here are the commands to create a password-secured certificate (.PFX)

$cert = New-SelfSignedCertificate -Subject "mydomain.local" -DnsName mydomain.local, *.mydomain.local -CertStoreLocation Cert:\LocalMachine\My -NotAfter (Get-Date).AddYears(10)
$pwd = ConvertTo-SecureString -String "passw0rd!" -Force -AsPlainText
$path = "Cert:\LocalMachine\My" + $cert.thumbprint
Export-PfxCertificate -cert $path -FilePath c:\temp\cert.pfx -Password $pwd
  1. Open a Powershell window with Admin rights.
  2. Paste and update the following line with the name of your domain (we’re using “mydomain.local” as an example)
$cert = New-SelfSignedCertificate -Subject "mydomain.local" -DnsName mydomain.local, *.mydomain.local -CertStoreLocation Cert:\LocalMachine\My -NotAfter (Get-Date).AddYears(10)
  1. Store the encrypted password in memory:
$pwd = ConvertTo-SecureString -String "passw0rd!" -Force -AsPlainText
  1. Determine the location for the newly created certificate:
$path = "Cert:\LocalMachine\My" + $cert.thumbprint
  1. Finally, update the -FilePath in the command below and export your new password-protected certificate so you can import it later.
Export-PfxCertificate -cert $path -FilePath c:\temp\cert.pfx -Password $pwd

Test your new certificate

  1. At a Windows Run screen (Win + R), type “certlm.msc”. This will open the Local Machine’s Certificate Store.
  2. Open “Personal” > “Certificates”
  3. Find the certificate you just created and open it.
  4. Double-check that the “Subject Alternative Name” (DNS Names) has your main site plus wildcard entries for sub-domains.
    Certificate Details
  5. Open a browser and go to your site using HTTPS (mine is https://mydomain.local) and verify that you can access it. If you need help binding the certificate to your IIS site, I will have instructions in part two of this blog.
    Certificate Display Test
  6. If you are still seeing validation issues, I have found that copying or importing the certificate into the “Trusted Root Certification Authorities” > “Certificates” folder works. Other times, waiting for my machine to register the new certificate has given good results in getting it to work.

Important Note!!

DO NOT use a Self-Signed Certificate for a public app or website. They can be easily compromised and are not intended to be used for public-facing sites. 4

How to set up local HTTPS for Optimizely, IIS, and Kestrel now available in part 2!


1 “Stop the ‘Page Contains Secure and Nonsecure Items’ Warning,” 2014.
2 yesman. “Using New-SelfSignedCertificate for Wildcard Certificates.” Stack Overflow, June 9, 2016.
3 Petri IT Knowledgebase. “Create a self-signed certificate using PowerShell,” August 10, 2016.
4 Keyfactor. “What Is a Self-Signed Certificate? Advantages, Risks & Alternatives,” October 14, 2021.,signed%20certificate%20creates%20serious%20risk..

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Nick Hamlin, Lead Technical Consultant

Nick Hamlin is a Lead Technical Consultant with Perficient. He has been programming for over 20 years, focusing on Optimizely CMS and Commerce since 2018. In his free time, he enjoys playing bar trivia, writing music, cooking, and finding cheap airfare to travel the world. Nick is fluent in English & Spanish and has studied French, Portuguese, and German.

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