• Friday, October 1, 2021

On September 30 2021, there will be a small change in how older browsers and devices trust Let’s Encrypt certificates. If you run a typical website, you won’t notice a difference - the vast majority of your visitors will still accept your Let’s Encrypt certificate. If you provide an API or have to support IoT devices, you might have to pay a little more attention to the change.

Let’s Encrypt has a “root certificate” called ISRG Root X1. Modern browsers and devices trust the Let’s Encrypt certificate installed on your website because they include ISRG Root X1 in their list of root certificates. To make sure the certificates we issue are trusted on older devices, we also have a “cross-signature” from an older root certificate: DST Root CA X3.

When we got started, that older root certificate (DST Root CA X3) helped us get off the ground and be trusted by almost every device immediately. The newer root certificate (ISRG Root X1) is now widely trusted too - but some older devices won’t ever trust it because they don’t get software updates (for example, an iPhone 4 or an HTC Dream). Click here for a list of which platforms trust ISRG Root X1.

DST Root CA X3 will expire on September 30, 2021. That means those older devices that don’t trust ISRG Root X1 will start getting certificate warnings when visiting sites that use Let’s Encrypt certificates. There’s one important exception: older Android devices that don’t trust ISRG Root X1 will continue to work with Let’s Encrypt, thanks to a special cross-sign from DST Root CA X3 that extends past that root’s expiration. This exception only works for Android.

The main determining factor for whether a platform can validate Let’s Encrypt certificates is whether that platform trusts ISRG’s “ISRG Root X1” certificate. Some platforms can validate our certificates even though they don’t include ISRG Root X1, because they trust IdenTrust’s “DST Root CA X3” certificate. After September 2021, only those platforms that trust ISRG Root X1 will continue to validate Let’s Encrypt certificates (with the exception of Android).

Test your site with SSL Labs' Server Test. If that doesn’t identify the problem, ask for help in our Community Forums.

If you have any questions about the upcoming expiration, please post to this thread on our forum.


Certificate Compatibility


Platforms that trust ISRG Root X1

Windows >= XP SP3 (assuming Automatic Root Certificate Update isn’t manually disabled)

macOS >= 10.12.1

iOS >= 10 (iOS 9 does not include it)

iPhone 5 and above can upgrade to iOS 10 and can thus trust ISRG Root X1

Android >= 7.1.1 (but Android >= 2.3.6 will work by default due to our special cross-sign)

Mozilla Firefox >= 50.0

Ubuntu >= xenial / 16.04 (with updates applied)

Debian >= jessie / 8 (with updates applied)

Java 8 >= 8u141

Java 7 >= 7u151

NSS >= 3.26

Browsers (Chrome, Safari, Edge, Opera) generally trust the same root certificates as the operating system they are running on. Firefox is the exception: it has its own root store. Soon, new versions of Chrome will also have their own root store.

 

Platforms that trust DST Root CA X3

Windows >= XP SP3

macOS (most versions)

iOS (most versions)

Android >= v2.3.6

Mozilla Firefox >= v2.0

Ubuntu >= precise / 12.04

Debian >= squeeze / 6

Java 8 >= 8u101

Java 7 >= 7u111

NSS >= v3.11.9

Amazon FireOS (Silk Browser)

Cyanogen > v10

Jolla Sailfish OS > v1.1.2.16

Kindle > v3.4.1

Blackberry >= 10.3.3

PS4 game console with firmware >= 5.00

You may want to visit this 2015-2017 community forum discussion for more information about compatibility.

 

Known Incompatible

Blackberry < v10.3.3

Android < v2.3.6

Nintendo 3DS

Windows XP prior to SP3

cannot handle SHA-2 signed certificates

Java 7 < 7u111

Java 8 < 8u101

Windows Live Mail (2012 mail client, not webmail)

cannot handle certificates without a CRL

PS3 game console

PS4 game console with firmware < 5.00