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Let's Encrypt root certificate expiration: how to continue using Diawi on iOS <10

On and all our subdomains, we use Let's Encrypt to generate SSL certificates and provide navigation through secure HTTPS connexions. However, on September 30, 2021, the root certificate used by Let's Encrypt to sign their SSL certificates has expired on some older systems like iOS <10.

To continue using Diawi (and many many other websites) on those older iOS devices, there is a solution!

When you navigate to, if you get a Cannot verify server identity popup with Cancel, Details and Continue options: you are affected. You could tap on Continue to visit the page, but since Diawi uses an Apple process for app installation that is not handled by Safari but the system, the installation will fail anyway.

In order to visit Diawi and install apps, the solution is to download and install the new root certificate manually on the device from this official Let's Encrypt address: (you will have to tap Continue when the "Cannot verify server identity" popup appears on that address).

Then tap on the Install button for the ISRG Root X1 certificate and it will become marked in green as "Verified".

That's it. The new certificate is valid until 2035 and you are able to continue using Diawi.

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About Greg
Paris, France Website
App deployment ninja, maintainer of Diawi and huge coffee lover.