UPDATE: Timelines in this post were updated in March 2020 and October 2020 to reflect the best available information.
HTTPS traffic is encrypted and protected from snooping and modification by an underlying protocol called Transport Layer Security (TLS). Disabling outdated versions of the TLS security protocol will help move the web forward toward a more secure future. All major browsers (including Firefox, Chrome, Safari, Internet Explorer and Edge Legacy) have publicly committed to require TLS version 1.2 or later by default starting in 2020.
Starting in Edge 84, reaching stable in July 2020, the legacy TLS/1.0 and TLS/1.1 protocols will be disabled by default. These older protocol versions are less secure than the TLS/1.2 and TLS/1.3 protocols that are now widely supported by websites:
To help users and IT administrators discover sites that still only support legacy TLS versions, the
edge://flags/#show-legacy-tls-warnings flag was introduced in Edge Canary version 81.0.392. Simply set the flag to Enabled and restart the browser for the change to take effect:
Subsequently, if you visit a site that requires TLS/1.0 or TLS/1.1, the lock icon will be replaced with a “Not Secure” warning in the address box, alongside the warning in the F12 Developer Tools Console:
As shown earlier in this post, almost all sites are already able to negotiate TLS/1.2. For those that aren’t, it’s typically either a simple configuration option in either the server’s registry or web server configuration file. (Note that you can leave TLS/1.0 and TLS/1.1 enabled on the server if you like, as browsers will negotiate the latest common protocol version).
In some cases, server software may have no support for TLS/1.2 and will need to be updated to a version with such support. However, we expect that these cases will be rare—the TLS/1.2 protocol is now over 11 years old.
Obsolete TLS Blocks Subdownloads
Often a website pulls in some page content (like script or images) from another server, which might be running a different TLS version. In cases where that content server does not support TLS/1.2 or later, the content will simply be missing from the parent page.
You can identify cases like this by watching for the message
net::ERR_SSL_OBSOLETE_VERSION in the Developer Tools console:
Group Policy Details
Organizations with internal sites that are not yet prepared for this change can configure group policies to re-enable the legacy TLS protocols.
For the new Edge, use the SSLVersionMin Group Policy. This policy will remain available until the removal of the TLS/1.0 and TLS/1.1 protocols from Chromium in May 2021. Stated another way, the new Edge will stop supporting TLS/1.0+1.1 (regardless of policy) in May 2021.
For IE11 and Edge Legacy, the policy in question is the (dubiously-named) “Turn off encryption support” found inside Windows Components/Internet Explorer/Internet Control Panel/Advanced Page. Edge Legacy and IE will likely continue to support enabling these protocols via GP until they are broken from a security POV; this isn’t expected to happen for a few years.
IE Mode Details
The New Edge has the ability to load administrator-configured sites in Internet Explorer Mode. IEMode tabs depend on the IE TLS settings, so if you need an IEMode site to load a TLS/1.0 website after Spring of 2021, you’ll need to enable TLS/1.0 using the “Turn off encryption support” group policy found inside Windows Components/Internet Explorer/Internet Control Panel/Advanced Page.
If you need to support a TLS/1.0 site in both Edge and IE Modes (e.g. the site is configured as “Neutral”), then you will need to set both policies (SSLVersionMin and “Turn off Encryption Support”).
Thanks for your help in securing the web!