How do web browsers remember which links have been clicked (and thus, color them purple/differently)?
As of this week, all links in my Google searches have suddenly turned purple, as if they've all been clicked before (even ones I've never clicked). Clicking them doesn't change the color.
My musings —
Is it merely a direct comparison of displayed links to the user's browsing history (handled by the browser)? Is there some sort of clicked-link cache? Is the information local, or is there server involvement (like with headers/cookies)?
Note:
I'd prefer to keep my browsing history and not have to wipe/clear it in the hope that it'll somehow fix the issue. Hence why I'm trying to get at the heart of the issue by backtracking how the links are colored purple/blue in the first place.
In a couple of cursory Google searches, it appears that others are having this problem, and even as of 2013-07-05.
Best Answer
I tested this with Bing and Google search engines in Chrome and Internet Explorer. I initially thought it was just Google that did it, because I hardly ever use any other engine. I found that when I searched Stack Overflow in Bing, it was already purple in both Internet Explorer and Chrome after I had clicked the link from the Google engine (hopefully that's not too confusing).
With that being said, it is indeed each browser that manages the color, but I am very intrigued as to how it works as well. To test this, I then proceeded to clear each individual history item in Chrome's clear history setting and checked the color. To my surprise, when I checked the box "Empty the Cache" the link still remained purple after I refreshed the page. It was actually the box "Clear Browsing History" that returned the links to blue. I tried this in Internet Explorer as well, and the links only returned to blue when only the "History" check-box was checked and the browsing history was cleared, not the "Temporary Internet Files" or "Cookies" check-boxes.
So to answer your question, I would probably say that it is a direct comparison of the user's browsing history data. There could be more to it, but hopefully that helped.