Troubleshooting the "allow-insecure-localhost" Flag in Microsoft Edge

The "allow-insecure-localhost" flag in Microsoft Edge is a crucial setting for developers who need to test applications using self-signed SSL certificates on their local development environments. This flag allows the browser to bypass the usual security checks for localhost, enabling developers to work without the hassle of valid, trusted certificates during development. However, recent versions of Microsoft Edge have seen changes to this flag, causing confusion and frustration among developers.

The Disappearing Flag: What Happened?

In Microsoft Edge Version 88.0.705.50, many developers noticed the disappearance of the "allow-insecure-localhost" flag from edge://flags. This meant they could no longer easily allow insecure SSL certificates for localhost, disrupting their development workflow.

Temporary Expiration and Re-emergence

The removal of the flag turned out to be an unintentional expiration. Later versions of Edge, such as 89.0.767.0, saw the flag return. This was due to a fix implemented in the Chromium project, which Edge is based on. However, the flag's lifespan was limited.

The Permanent Removal in Later Versions

As of Edge v134, the "allow-insecure-localhost" flag is no longer available. The flag was set to expire in M130, and as M130 flags are now permanently expired, the setting is gone.

Workarounds for Different Edge Versions

Depending on the version of Microsoft Edge you are using, different workarounds exist to allow insecure localhost connections:

• Edge v119-133:
  • Go to edge://flags.
  • Search for the flag "Temporarily unexpire M130 flags" (or "M118" for Edge v119-120) and enable it.
  • Restart the browser.
  • Search for "#allow-insecure-localhost" again. It should now be visible.
  • Enable the flag and restart the browser again.
• Edge v133 and later:
  • Using Policies: Modify Edge's policies to allow insecure connections.
    • Navigate to edge://policy.
    • Use the SSLErrorOverrideAllowedForOrigins policy.
    • Set the policy to ["https://localhost"].
    • Alternatively, use the broader SSLErrorOverrideAllowed policy.
    • These policies can be set in Intune or directly in the registry. Refer to the Microsoft Edge policies documentation for detailed instructions.

Alternative Solutions

• Edge Dev Channel: Using the Edge Dev channel (Microsoft Edge Insider Downloads) can sometimes provide a temporary workaround, as the Dev builds might have different flag configurations.
• Using other browsers: Consider using browsers such as Firefox which still provide easy ways to bypass SSL certificate checks for localhost.

Why is This Important?

The ability to easily bypass SSL certificate checks for localhost is vital for web developers. It allows them to:

• Test secure features locally: Develop and test features that require HTTPS without needing to purchase or generate trusted certificates for a local environment.
• Speed up development: Avoid constant interruptions and certificate-related errors during the development process.
• Simulate production environments: Accurately mimic production HTTPS environments on their local machines for testing and debugging.

The Importance of Secure Development

While disabling security checks for localhost can be convenient, it's crucial to remember the importance of secure development practices. Always ensure that your application uses proper SSL certificates in production and that you understand the security implications of bypassing these checks, even in development environments.

By understanding the changes to the "allow-insecure-localhost" flag and utilizing the appropriate workarounds, developers can continue to efficiently develop and test their applications using Microsoft Edge. Remember to stay updated with the latest browser versions and security best practices to ensure a smooth and secure development workflow.