Privacy @lemmy.ml TootSweet @lemmy.world 1 day ago

(Solved) How Does YouTube Know Where I Left Off On A Video?

Yesterday, I started watching a video on YouTube but closed out of my browser (Firefox) only a few minutes into the video.

I've got my Firefox set to delete all cookies, history, form data, etc on every close. (Pretty much everything but bookmarks.) The image on this post is a screenshot of my relevant settings.

Today, after having exited my browser and fully shut down my computer for a while, I remembered the video and decided to continue watching it.

In Firefox, I searched for the video (I used the search term "gnu taler" -- something worth looking into especially for folks interested in this particular Lemmy community by the way). In the search results, the video I was searching for showed the red bar at the bottom indicating I'd watched only the first few minutes of it.

Which seems weird given that I'd cleared all my browser data since I watched the first few minutes.

So I did some experimentation. I closed my browser completely again and opened it back up, searched in YouTube, and it still had the indicator. I updated to the latest version of Firefox in the Arch package repository. Same indicator. I tried the same in Chromium (which I've also got set to delete all browser data on close). Still the indicator. I installed Tor Browser Bundle (specifically torbrowser-launcher on Arch Linux), changed none of the default settings at all, and searched in YouTube. The indicator is present. In Tor Browser Bundle.

Anybody have any idea how that's possible?

My only guesses are:

That search is so niche as to be literally unique (which if true makes me sad -- I really hope GNU Taler takes off and becomes widespread) and YouTube is using that to identify me.
YouTube doesn't know where I left off at all. Not even my browser knows (because if it was my browser keeping track, it wouldn't persist between browsers). It's something else on my system that my browsers depend on or tap into.

The only other pieces of relevant info I can think to share:

There's another video (also about GNU Taler) that I watched all the way through the same day that I started the video this post is about. It doesn't show any indicator.
I tried searching on my phone's browser. No indicator. But then I'm not sure my phone ever shows indicators. I haven't tried this on any other devices on my network or anything.
I still haven't watched the video in question. Heh.

Thanks in advance for any insight you might have.

Edit: Sorry for neglecting to mention previously that at no point during any of the above did I log in to YouTube. And the "Sign in" button was visible at the top of the page indicating I wasn't logged in. Since multiple people asked, I figured I should edit my OP with that info.

Edit2: Two more things to mention. I think some folks are thinking I copied the link and pasted it between browsers during the above test or something? The only reason the timestamp is included in the link I posted above is because when I copied it into this post, I didn't think to remove the timestamp. But I didn't do anything like copying the link from the search results in one browser and then paste the link into TBB or anything. In each separate browser, immediately after opening the browser, I went to YouTube (by typing "youtube.com<enter>" into the address bar) and put "gnu taler" into the search bar and hit enter. And in each browser, YouTube somehow remembered where I'd left off in a whole different browser -- with a different IP address in the case of the switch from Chromium to TBB. And no urls were copied between browsers in any of the above.

The other thing to mention. Changing my search term to the full title of the video ("Building an Open Source Payment System - Sebastian Javier Marchano, Taler System" sans quotes) gives the relevant video as the top search result, but no "left off" indicator. And I'm in the Firefox in which I first noticed it had remembered.

Oh, actually, one more thing to mention. After posting this, I continued watching. I'm probably about 3/4 done with it now. But I closed my browser again before completing it, reopened my browser, and searched "gnu taler". It gives the indicator, but the position of the indicator is roughly (possibly exactly) where it was when I first noticed it had remembered. Not where I left off after watching to roughly the 3/4 mark.

Edit3: Wow! Ok. I'm 99% sure folks smarter than me have hit upon what's going on here. Thanks in particular to Tony N and Chozo for the right answer. It looks like YouTube has a feature where, depending on your search terms, it may automatically skip you a certain ways into the video. (Like "oh, you searched for 'gnu taler'? Well, in this video result, this bit in the middle is the part that's relevant to your search terms, so we'll just start you such-and-such-many seconds into the video.") The red bar doesn't mean "you've watched this" at all. And YouTube isn't "remembering me" between browsers. It's just consistently (as long as I use the specific search terms "gnu taler") suggesting that I start that video 273 seconds in rather than from the beginning. And anyone who searches that exact search term should get similar results... unless they're on mobile for some weird reason? That paired with the coincidence that I'm pretty sure I just happened to have stopped the video yesterday right about at the same place where YouTube recommends you start had me very confused. Whatever the case, I'm satisfied this must be the right answer. Thanks again, ya'll!

23 comments

YouTube isn't remembering your progress for this video. I just opened an incognito window and searched YouTube for "gnu taler" as you mention, and in my results I see the same progress bar. I've never seen this video before, and certainly have never watched it.

For some reason, YouTube is adding a timestamp argument to the URL within the search results. Not sure why, maybe it's a "smart" detection of moving you to the spot in the video that's relevant to the term "gnu taler". But it certainly has nothing to do with you, specifically.
- Why do they keep making bad decisions??????
- This is the right answer. It happens to me all the time when I search for something very specific.
- https://www.youtube.com/watch?v=tFhn3IO23lE&t=273s&pp=ygUJZ251IHRhbGVy
  
  &t=273s means 273 seconds, removing that should start the video from the beginning
  
  https://www.youtube.com/watch?v=tFhn3IO23lE&pp=ygUJZ251IHRhbGVy
Unless I'm missing something, the timestamp in the URL (t=273s) jumps the video to 273 seconds into the video. The link itself is what remembers where to start the video.
- I think OP is referring to the little red progress bar that appears at the bottom of a youtube thumbnail, which appears before you follow any link, timestamped or not, to the video
- Not sure I understand what you're getting at here.
  
  Yes, I linked to the video and didn't think to remove the t=273s bit when I included the link in the OP. And, yes, I understand that having a &t=273s in the url makes it start not right at the beginning. My question is how did it know where to start (and how much red bar to show on the video thumbnail in the search results) given that my cookies had been deleted and, on subsequent tests, I even switched browsers.
  
  I was purposefully telling my browsers to forget all the information YouTube could use to remember that and it still remembered somehow.
  
  Now, I am concerned regarding the privacy aspect of how on earth it still persisted in TBB. But even when sites fingerprint you, if you delete your cookies they almost always at least pretend not to know you when you visit. I'd expect YouTube/Google to use fingerprinting to sell my information and do targeted advertising or whatever. But it's weird that they'd even let on to me that they had figured out who I was even though I wasn't sending them any cookies.
  
  When I search YouTube for GNU Taler, it gives me the same video with the same timestamp on the red bar. (273 seconds) It's not where I stopped watching it, I've never watched it. It's just the part of the video where they start talking about GNU Taler.
Google is more than capable of uniquely identifying your system without cookies or any other client-side storage. Browser fingerprinting is widespread.

Also, did you return to that video with the same IP address as when you first watched it?

I'll just assume you didn't log in to youtube when watching. :)
- Maybe your system, not everyone's.
  
  Pedantic. (And I didn't say everyone's, did I?)
  
  Practically everyone's when playing videos on YouTube.
- Also, did you return to that video with the same IP address as when you first watched it?
  
  That's (part of) why I tried Tor Browser Bundle, though. Because it would give me a different IP address. (And when I visited YouTube via TBB, it gave me the little superscript after the YouTube logo indicating a different country than I was in.)
  
  I’ll just assume you didn’t log in to youtube when watching. :)
  
  Ha! Should have thought to mention that. But yes, you're right. I didn't log in or anything. (And for that matter, in every test I did, when I first got to the home page, I got the "search to get started" prompt that YouTube gives as of pretty recently when you don't have any cookies on visiting the index page.)
  
  I'm sure it's tedious, but run those tests again, and when you do, before and after watching the video, go to https://www.youtube.com/feed/history and see if it tracked it. I understand you're logged out, but maybe you're somehow selected for a test of some sort of logged out experience.
  
  That being said, I ran through your replication steps and could not reproduce it (even down to pulling up the same video). I also doubt that Youtube would create a feature useful for people logged out of their service, since they want to encourage you to log in because they get better data for selling ads.
It doesn't remember my spot even when I'm watching in their app logged into an account. Is it even a feature they offer?
I assume you're not, but you aren't logged in are you?

Otherwise I'd say fingerprinting or identifying your machine like another commenter suggested
- Yeah, forgot to mention I hadn't logged in or anything. But that's right. I didn't log in during any of that testing. I've edited that detail in.
  
  Still weird that it could possibly fingerprint even while using TBB, though.
~~Are you logged into Youtube/Google?~~ EDIT: I see your comment in another reply saying you're not logged in. Keeping the rest of my comment below for posterity

Youtube keeps a watch history, and allows you to resume videos where you left off of. This works across devices if you're logged in. This functionality is enabled by default, and can be turned off in https://myactivity.google.com/

https://support.google.com/youtube/answer/95725

These settings are on an account level and tracked server side. Since the history can be accessed across devices, the browser you use and cookie retention have no effect on the ability for the viewing history to be retained.
Start by first not using Google YouTube. Next switch to librewolf

Anyway the link has a time stamp in it. Look at the t parameter
- Right, the link has a timestamp in it. But I don't know how the search results page knew what timestamp to put in the link to the video even after switching to TBB.
I've had YouTube load in a new incognito tab where I left off, then revert back to the start half a second later. Google just being google

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