What's the best way to implement SSL on an existing 2.0.15 site, without breaking anything?

I see you already have ssl on the site

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You can add this to an .htaccess file in your forum folder if you have one, this will force ssl throughout your site.
RewriteEngine On
RewriteCond %{HTTPS} !=on
RewriteRule ^(.*)$ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301,NE]

Run repair settings https://wiki.simplemachines.org/smf/Repair_settings.php

change all the urls, then add a redirect to your htaccess file.

And perhaps take a read of, https://www.simplemachines.org/community/index.php?topic=555034.0

@lesmond yes there is an SSL certificate in existence there, indeed.

@lurkalot Thanks its been a while since I've used repair settings.

I had a look at that community link @lurkalot  but couldn't see in that anything specific to SSL/https ?
 
So I use that and it offers an option to convert all URLs from http to https ?
The once that's done, use the htaccess file (as per @lesmond post)  to force https. 

Correct?


(I have done my 2.1 forum as SSL which was easy as there is an option in the forum settings to force https throughout the site   )

Quote from: LandyVlad on May 26, 2019, 07:47 PMSo I use that and it offers an option to convert all URLs from http to https ?
The once that's done, use the htaccess file (as per @lesmond post)  to force https. 

Correct?

Yes.

You'll also want to check for posted links and images that use http. They may stop your site from showing as secured.

That's what the image proxy feature is for...