In-app browsers are components of mobile applications allowing display and limited browsing of web content within an app, all without opening an actual browser.
When you click on a link in an app, such as Facebook for example, instead of opening this link in your device’s browser, its content will be displayed within the app’s “browser”.
Sometimes, images aren’t don’t get displayed when they are opened in these browsers. This usually happens because your images are served on pages loaded over https using http, which isn’t a secure protocol, and this creates mixed content errors.
To resolve this issue, you can edit your .htaccess file located in the root of your website, and add the following code:
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteCond %{HTTPS} !on
RewriteCond %{HTTP:X-Forwarded-Proto} !=https
RewriteRule ^.*$ https://%{HTTP_HOST}%{REQUEST_URI} [L,QSA,NE]
</IfModule>
<IfModule mod_headers.c>
Header set Content-Security-Policy “upgrade-insecure-requests;”
</IfModule>
It will force the images to be served over https, which eliminates the mixed content errors and makes your images appear as intented.