5 ms·

Facebook visits pages that you post in messages and stays for many seconds

24 points by antoineMoPa 10y ago

taneq 10y ago
Um yeah, the moment you type/paste a link in a post, it loads a preview and tries to pick a good representative picture of the page. As far as I can tell the image is even mirrored on Facebook's CDN for faster loading. It's not like they're subtle about it.
- squiggy22 10y ago
  Correct. This is the open graph bot. You can force fb to scrape your site at will and clear the current cached image preview. https://developers.facebook.com/tools/lint https://developers.facebook.com/tools/lint
- antoineMoPa 10y ago
  This is the part that happens before you send the message. The post is talking about the automated browser that visits the link after you post it and waits for 15 seconds with socket.io (thus javascript activated).
  - taneq 10y ago
    Oh. Something to do with trackbacks then, maybe?
omarforgotpwd 10y ago
Facebook probably sends an HTTP request to the link to get an image preview. I doubt that any human or computer is actually "looking" at the link for 15 seconds, more likely they just messed with the concept of time on the preview agent's Javascript interpreter so they can determine the layout of the "final page" with all animations and JS completed.
powera 10y ago
This is not secret, surprising, or newsworthy, and the implication that it's for the NSA is pure conspiracy theory.
killwhitey 10y ago
Previous discussion: https://news.ycombinator.com/item?id=11875419 https://news.ycombinator.com/item?id=11875419
- powera 10y ago
  That seems different? Exposing (possibly private) URLs in messages via the API seems like a bug (though int64s aren't really guessable when you have DoS protection). Just visiting the link shared is completely normal behavior.
lbrandy 10y ago
> But why? Go ahead and post a link in a message (I chose this one: http://imgur.com/gallery/wjANVCD http://imgur.com/gallery/wjANVCD). A little visual preview will appear. Where do you think this comes from? > And classify you as a good citizen for the NSA so that you don’t get killed in a drone attack Or maybe that.
- pshc 10y ago
  Occam's Razor strikes again.
- antoineMoPa 10y ago
  Why stay for so long though? Fetching an image is fast and using an automated browser is a bit overkill. Maybe they wait for 15 seconds in case the server is slow...
  - powera 10y ago
    Anti-virus. The post seems to be complaining that Facebook is using a browser, which probably means they're testing for malware.
  - GauntletWizard 10y ago
    Or to detect JavaScript triggered malware or other nefarious behavior. Running a full headless browser for link scanning is actually quite doable for Facebook's scale.
  - morgante 10y ago
    There are definitely some sites (particularly news sites) which can take 15 seconds to actually render the main content of the page.
  - corecoder 10y ago
    JavaScript, webfonts, XHR... In my experience, if you don't wait most of the times you get a blank page.
  - kochthesecond 10y ago
dack 10y ago
I don't think this is a big deal. You're posting a message _on their site_. It's reasonable for them to inspect the url.
umhan35 10y ago
I guess it stays for many seconds because it waits JavaScript to finish executing to get an image preview. It's not uncommon that some sites needs many seconds (or even longer) to load.
awqrre 10y ago
also, if you want a URL to stay private, don't email it to anyone using a cloud email service (including yourself)...

24 points by antoineMoPa 10y ago

taneq 10y ago

Um yeah, the moment you type/paste a link in a post, it loads a preview and tries to pick a good representative picture of the page. As far as I can tell the image is even mirrored on Facebook's CDN for faster loading. It's not like they're subtle about it.

squiggy22 10y ago
Correct. This is the open graph bot. You can force fb to scrape your site at will and clear the current cached image preview. https://developers.facebook.com/tools/lint https://developers.facebook.com/tools/lint
antoineMoPa 10y ago
This is the part that happens before you send the message. The post is talking about the automated browser that visits the link after you post it and waits for 15 seconds with socket.io (thus javascript activated).
- taneq 10y ago
  Oh. Something to do with trackbacks then, maybe?

omarforgotpwd 10y ago

Facebook probably sends an HTTP request to the link to get an image preview. I doubt that any human or computer is actually "looking" at the link for 15 seconds, more likely they just messed with the concept of time on the preview agent's Javascript interpreter so they can determine the layout of the "final page" with all animations and JS completed.

powera 10y ago

This is not secret, surprising, or newsworthy, and the implication that it's for the NSA is pure conspiracy theory.

killwhitey 10y ago

Previous discussion: https://news.ycombinator.com/item?id=11875419 https://news.ycombinator.com/item?id=11875419

powera 10y ago
That seems different? Exposing (possibly private) URLs in messages via the API seems like a bug (though int64s aren't really guessable when you have DoS protection). Just visiting the link shared is completely normal behavior.

lbrandy 10y ago

> But why? Go ahead and post a link in a message (I chose this one: http://imgur.com/gallery/wjANVCD http://imgur.com/gallery/wjANVCD). A little visual preview will appear. Where do you think this comes from? > And classify you as a good citizen for the NSA so that you don’t get killed in a drone attack Or maybe that.

pshc 10y ago
Occam's Razor strikes again.
antoineMoPa 10y ago
Why stay for so long though? Fetching an image is fast and using an automated browser is a bit overkill. Maybe they wait for 15 seconds in case the server is slow...
- powera 10y ago
  Anti-virus. The post seems to be complaining that Facebook is using a browser, which probably means they're testing for malware.
- GauntletWizard 10y ago
  Or to detect JavaScript triggered malware or other nefarious behavior. Running a full headless browser for link scanning is actually quite doable for Facebook's scale.
- morgante 10y ago
  There are definitely some sites (particularly news sites) which can take 15 seconds to actually render the main content of the page.
- corecoder 10y ago
  JavaScript, webfonts, XHR... In my experience, if you don't wait most of the times you get a blank page.
- kochthesecond 10y ago

dack 10y ago

I don't think this is a big deal. You're posting a message _on their site_. It's reasonable for them to inspect the url.

umhan35 10y ago

I guess it stays for many seconds because it waits JavaScript to finish executing to get an image preview. It's not uncommon that some sites needs many seconds (or even longer) to load.

awqrre 10y ago

also, if you want a URL to stay private, don't email it to anyone using a cloud email service (including yourself)...