Since KA uses a YouTube player, I imagine your YouTube settings could make a difference.

1. Go to your Account Settings page.

2. Select Playback from the left-hand menu.

3. Check or uncheck Always show captions.

4. Check Show automatic captions by speech recognition (when available) to enable automatic captions for videos that don't already have captions provided.

5. Click Save.

Let me know if this works for you!

The above answer does nothing but change your default settings for direct youtube videos. Khanacademy has a glitch that auto activates subtitles. Needs a fix. Is there a way to report this bug (not that I doubt they already know about it.)? It seems such a small thing and yet is terribly annoying.

Hi Marc, you can report this to staff here:
https://khanacademy.zendesk.com/hc/en-us/requests/new

I had the same issue and it was so annoying I found a script to resolve it. 

https://gitlab.com/zalent/khanacademy-disable-sub

I still haven't found a way to automatically start the videos at 2x speed, which I would really like. Perhaps these can be added as settings.

I mainly watch videos in the iPad app, but sometimes I watch them on the website in either Safari on the iPad or Chrome on a Windows 10 computer. I have found that when I turn off captions, they stay off for me. This is true in all three platforms. When you refer to subtitles, do you actually mean captions, which are the onscreen text in the same language as what is being spoken, or do you mean subtitles in the theatrical movie sense in which a translation of what is being said in the video is what is displayed on the screen? If this is what you are referring to, I have not used them on Khan Academy, so I don’t know how to turn them off or on and how to keep them off. But if you are referring to same language captions, it could be that something on your platform (maybe cookies) is keeping the changes from transferring across videos.

Yes we're referring to Closed Captioning. But that's interesting that you're not having the same issue. I am using Chrome on Windows 10 and I resorted to a greasemonkey script for the fix. Do you have any further advice for me to check if this is a cookie thing?

I don't usually touch cookies because I don't want to lose certain settings. I suggest you report this using the "Report a Problem" link here in the Help Center. They may be able to give you a step-by-step procedure to check cookies.

Okay,

So, I experienced the same problem. The YouTube video popups through the Khan Academy platform (NOT the Khan Academy YouTube channel itself) were constantly forgetting that I had previously disabled the Closed Captions option (some people are describing them as 'Subtitles'). This is was a small annoyance but something I felt that should have been trivial to solve.

The first suggestion was something that had already been mentioned and that's to go in to your own particular YouTube Account settings and to disable "Always show captions" in the Playback settings section. That doesn't have any effect.

The real problem: Cookies. Websites store cookies to save information about your visit to the website. Ask yourself: What blocks/disables cookies other than the browser itself? Ad Blockers. Why? Malicious ads can potentially read personal/confidential information about you and some ad blockers will go as far as to disable generic cookies on all websites as a blanket rule in order to protect you from malware or big data companies along aside the service of disabling advertisements from your videos and websites. Ad Blocker cookie management conflicts are actually a very common issue that many users face with website functionality as opposed to conflicts with the browser's own cookie settings, which most common users don't modify.

So, obviously, the solution is to disable your adblocker for Khan Academy. Do you have an ad blocker installed on your browser? Well, it's worth checking for an icon along the top bar of your browser. AdBlock Plus, Ghostery, UBlock Origin are common ad blockers. If you find one installed, simply left click on the icon while on any page of the Khan Academy website for a drop down menu with options. Almost all mainstream ad blockers will allow you to disable ad blocking for specific websites in the main drop down menu. Once you've disabled ad blocking, you might have to refresh the page or completely close/reopen your browser before the settings can take effect and you might also have to disable closed captions one more time.

I have a feeling that will be a solution to many others in the future. Good Luck! Cheers