Prevent http page from redirecting to https page
I have a website (userbob.com) that normally serves all pages as https. However, I am trying to have one subdirectory (userbob.com/tools/) always serve content as http. Currently, it seems like Chrome's HSTS feature (which I don't understand how it works) is forcing my site's pages to load over https. I can go to chrome://net-internals/#hsts and delete my domain from Chrome's HSTS set, and the next query will work as I want without redirecting to an https version. However, if I try to load the page a second time, it ends up redirecting again. The only way I can get it to work is if I go to chrome://net-internals/#hsts and delete my domain from Chrome's HSTS set after each request. How do I let browsers know that I want all my pages from userbob.com/tools/ to load as http? My site uses an apache/tomcat web server.
(Just FYI, the reason I want the pages in the tools directory to serve pages over http instead of https is because some of them are meant to iframe http pages. If I try to iframe an http page from an https page I end up getting mixed-content errors.)
Answer
HTTP Strict Transport Security (or HSTS) is a setting your site can send to browsers which says "I only want to use HTTPS on my site - if someone tries to go to a HTTP link, automatically upgrade them to HTTPS before you send the request". It basically won't allow you to send any HTTP traffic, either accidentally or intentionally.
This is a security feature. HTTP traffic can be intercepted, read, altered and redirected to other domains. HTTPS-only websites should redirect HTTP traffic to HTTPS, but there are various security issues/attacks if any requests are still initially sent over HTTP so HSTS prevents this.
The way HSTS works is that your website sends a HTTP Header Strict-Transport-Security with a value of, for example, max-age=31536000; includeSubDomains on your HTTPS requests. The browser caches this and activates HSTS for 31536000 seconds (1 year), in this example. You can see this HTTP Header in your browsers web developer tools or by using a site like https://securityheaders.io . By using the chrome://net-internals/#hsts site you are able to clear that cache and allow HTTP traffic again. However as soon as you visit the site over HTTPS it will send the Header again and the browser will revert back to HTTPS-only.
So to permanently remove this setting you need to stop sending that Strict-Transport-Security Header. Find this in your Apache/Tomcat server and turn it off. Or better yet change it to max-age=0; includeSubDomains for a while first (which tells the browser to clear the cache after 0 seconds and so turns it off without having to visit chrome://net-internals/#hsts, as long as you visit the site over HTTPS to pick up this Header, and then remove the Header completely later.
Once you turn off HSTS you can revert back to having some pages on HTTPS and some on HTTP with standard redirects.
However it would be remiss of me to not warn you against going back to HTTP. HTTPS is the new standard and there is a general push to encourage all sites to move to HTTPS and penalise those that do not. Read his post for more information:
https://www.troyhunt.com/life-is-about-to-get-harder-for-websites-without-https/
While you are correct that you cannot frame HTTP content on a HTTPS page, you should consider if there is another way to address this problem. A single HTTP page on your site can cause security problems like leaking cookies (if they are not set up correctly). Plus frames are horrible and shouldn't be used anymore :-)