Ask HN: What to do if you see your coworker job searching?

> For all I know he wasn't even looking at jobs for himself...

Or he could just be looking at what is out there. Keeping updated in case he wants to move on in the future. Smart move, if so.

Some companies are stupid enough to fire people the second they get sniff of them considering leaving.

You could get your colleague into serious trouble by reporting something that is neither your, nor your employer's business.

It happens, you don't know the back story.

Seriously though, it's none of your business, and everyone deserves the right to look at other positions, learn what they're worth/what's out there, and move to a new position if it will make them happy. If your coworker wants to leave, doing anything to keep them around is likely to end badly for all involved. If they do leave, look at it this way, you have expanded your network and now have a friend elsewhere in the industry who might someday look out for you!

Usually there are other signs as well when an employee is looking to leave (search online). When those confirm your suspicion you could consider talking about it. But from just a few open browser tabs I don't think you can draw conclusions (it may well have been recruiter spam that looked curious).

Also, I hope I never work with you.

I regularly take a look at what developer roles are on offer. It doesnt mean I want to leave my job.

I use it as a way to see what companies are using what technology.