HACKER Q&A
📣 Timothee

What do social networks put unique IDs in link sharing for?


When I copy a link to share a tweet, or a YouTube video or any number of websites, there's often an ID unique to me attached to the link. (YouTube even changes it for every share)

e.g. https://youtu.be/dQw4w9WgXcQ?si=2W5B4wtJZFr7-Ps4 (yes, it's Rick Astley)

I understand it's for tracking and analytics generally speaking, but practically, what do these sites really get from them?

The signals from me sharing a particular link, and others clicking it seem very minute and not very valuable. I suppose you could establish parts of a social network over time, but how valuable is that in practical terms? What can they do with that, that they couldn't do without? How is it worth it to add to all links and have the infrastructure to store and track and analyze?

Is it simply cheap enough that "why not"?

Thanks!

  👤 toast0 Accepted Answer ✓
I didn't do anything with link tracking when I was at FB, so I dunno what they do... But when I was at Yahoo, we instrumented all (or mostly all) the links on a page, so that we could see what links people were clicking on (in aggregate) and maybe figure out some session stuff, and we could tag things for analytics like cpcs and what not (went into the logs, not into the link tag), and then we could see for pages like X, revene was this, and all that kind of thing.

But we didn't get any value if a tag escaped into someone else's session, so we'd try our best to have the links be clean it you copied them, and try to make them clean in the address bar and all that. And if you were a robot u-a, then no tracking at all, clean links only.

👤 al_borland
Any time I copy a link to share with someone, I delete the ? and everything after. I want to send the person the link, not whatever metadata the site is trying to collect.
👤 gtirloni
Offer you and your network more relevant ads.
👤 moomoo11
Can't speak for YT but these sorts of identifiers are used for basically what you said - tracking and analytics in order to make more money, at scale.

Social media sites are concerned with one thing - ads.

That ID is probably stored somewhere in their backend. I'm sure 0.1% of users will strip that query param out (literally nobody does lol), but now their server has registered that you created a share link with si=1234

Now your friend Sally opens that link, and they register that this other user opened a share link with si=1234

What happens next is used to make more money.

👤 karmakurtisaani
I didn't realize they did this. So it means if I share a video with the identifier for example here, they can match my username here with my YouTube username. Since my real identity is known to them via gmail, I pretty much lose all anonymity here as well (in their eyes at least). Then,if there's ever a leak of that data, my online identity is entirely compromised.
👤 d--b
My guess is that a person that gets other people to click on links is given a higher “influence score”, or something like that.
👤 KomoD
> what do these sites really get from them? What can they do with that, that they couldn't do without?

Well they can attribute traffic more easily.

> Is it simply cheap enough that "why not"?

Well yeah that too, and the data is valuable.