Short Answer: Absolutely OK.

A little lengthier answer:
At my workplace, we routinely ask for a candidate’s Stack Overflow / Stack Exchange username. Contribution to the Stack Exchange community leaves a much clearer trail of where someone is at with their skills.

I know others who ask for GitHub accounts and refuse to accept candidates without a GitHub account*.

In our case, we won’t remove a candidate for consideration if they don’t have an account.

Ultimately, it’s just one piece of the interviewing puzzle as you’re trying to identify a match between the company’s needs and the candidate’s skills. It’s not a make-or-break factor; it merely helps confirm impressions made during the interview.

_{* To be clear, I don’t condone that approach, and I think it causes that team to miss out on otherwise well qualified candidates. I brought it up to point out having heard of more extreme stances and to show that just asking for a Stack Overflow account name is pretty mild in comparison.}

Some additional qualifiers based upon comments:

1. We don’t look at Meta Stack Overflow and meta type posts. Meta is different, and we understand that. It’s also really easy to miss the context behind those types of posts. IMO, they are closer to noise than signal when it comes to evaluating a candidate.

2. Likewise, comments and review activity aren’t considered. They lack context and they don’t have a meaningful correlation to the candidate’s ability to do the job.

3. We have found a solid correlation between a candidate’s performance in an interview and the level of Q&A that they engage in. Their Stack Overflow / Stack Exchange account becomes a supporting factoid, equivalent to a submitted code sample during the interview process.

Obligatory xkcd strip on interviews. Elaboration.

Asking point-blank what their SO user name is probably not appropriate. It would sound very direct, and I would find such a question a little invasive. Asking what online resources they use when they are problem-solving is much more appropriate. And if they answer that they are a StackOverflow user, then I think you could ask them how interactive they are. If they mention that they are an active ask-er/answer-er, then asking them what their username is would be appropriate.

I think it’s acceptable for an interviewer to ask, but if a candidate refuses then it shouldn’t be a deal-breaker.

Some people work with specialized, proprietary tools that don’t have any questions on StackOverflow (I just checked). Some people don’t have time to spend answering other people’s general questions. I know some developers who don’t ask or answer on SO mostly because of language barriers.

There are great developers out there who just don’t participate much in the StackExchange ecosystem.

It sounds like this opinion is not particularly popular, but I don’t think it is okay to ask for this information.

Stack Exchange is a place of learning; you shouldn’t have to worry about being judged for asking “dumb questions” later down the line. I know I come to Stack Exchange to broaden my knowledge, not just of programming, but in all sorts of subjects. As long as I’ve put in some effort to solve questions on my own, I shouldn’t have to feel self-conscious for asking a question that most experts on the subject would be expected to know the answer to.

Moreover, this would exacerbate the issue of users keeping multiple accounts, one for asking questions, and one for providing answers. I’ve already seen this a number of times on SE. I think users do it because they appear more knowledgeable with less questions asked.

I think it is mildly inappropriate to ask a candidate for information they did not volunteer (with a few obvious exceptions, like criminal background, etc.) It is also at least potentially dangerous, since in many places there are laws forbidding employment discrimination that limit what questions you can ask. If participation on a particular site turns out to correlate with race, age, gender or other category for which discrimination is forbidden then you are potentially opening yourself up to a lawsuit. You may even actually be factually committing such discrimination (almost certainly unintentionally).

According to this quick Google search result social media searches run the risk of an employer discovering information it is otherwise illegal to ask about, potentially exposing itself to a discrimination suit. In some places it is not legal to ask about disability or pregnancy. Since SO and SE are professional sites, it is more reasonable to claim that discrimination was not the purpose of the question, but…

I personally would ask something like “do you participate in any professional websites that you would like us to know about, but didn’t quite make it onto your resume?” And I would not regard it as a negative for those who had no such participation, other than that other candidates they are competing with might help themselves with their answer.

Would you consider it appropriate if you were asked for your Stack Exchange username in a SW job interview (or as a pre-interview screening question)?

Some good candidates will not have a StackExchange account. So if you can only offer onsite interviews to 5 people and expect 100 applicants, this might be a good strategy to simply provide a better way to distinguish initial candidates.

But do keep in mind you cannot eliminate candidates who do not have a StackOverflow account unless you are willing to take the risk of people who otherwise would be excellent candidates not having accounts.

If you want to use this as part of the interview process, I would strongly recommend it as one option of many – github and StackExchange are both potential (not comprehensive).

Just make sure this isn’t presented as mandatory.

I would volunteer MY profile it if possible in an interview as an interviewee. It can naturally come up in regards to questions about “do you code for fun?” or “what do you do to learn outside work?” or any question like that.

It does help to find these, though.

Also, keep in mind a StackExchange account can show two different stories*:

• Ability to ask meaningful questions
• Ability to provide meaningful answers

Both can be good or bad, depending on your profile and ratio of questions/answers.

*it also might show you spend way, way, WAY too much time on here…

Yes, but I think it would be most worthwhile as a pre-screening question. Realistically, you aren’t going to be able to act on the information during the interview in a meaningful way if that’s the first time you’re asking about it. It’d be like waiting until they were in the office to ask for code samples. The other benefit of being a pre-screening question is that if they do decide they don’t want to share it for whatever reason, they can make that decision without being on the hotseat.

In general, I think its a great/acceptable resource. If they do have one, it would make for excellent talking points during the interview itself, especially if you can find an answer they gave with a code sample, or if they’ve answered a few questions related to what they would be working on. This has the added advantage of being a specific topic they’ve clearly put some time into before, and developed a written answer to. (If that answer isn’t well formed or flat out wrong, that’s likewise a very useful indicator).

I think it’s reasonable for an employer to ask for it, but I don’t think its reasonable for that to be a make-or-break qualifier.

Joel mentions that a high rep equates to getting high paying jobs but by his own logic, unless you’re under employed you may not have time to flex your mental skills and get a large amount of rep. So the man who waxes poetic about Stack Exchange (and rightfully so) admits that it’s really an indicator of both high employability and under employment.

I do this all the time.

IMHO asking for online reputation sources is like asking for your resume, with one important difference: faking a good online reputation is way harder than faking a good resume.

Stack Exchange is a good place to find out about the candidate’s communication skills.

There’s nothing I respect more than a great programmer. But if you can manage to become a great programmer and a great communicator, there’s almost nothing you can’t accomplish. – Jeff Atwood

GitHub is where most high profile projects are hosted (at least for the technology stack we use), and if the candidate contributed to some of these projects it says a lot about the quality of his work (good projects will not accept pull requests lacking documentation and/or unit tests).

There may be cultural differences between Europe and the USA on this, but here’s my perspective on this…

When you are applying for a job, as a candidate you are wanting to present yourself, your experience and your ability to do the job in question. You are actively shaping how you are presented to make it a simple choice for the employer to say yes, this is our new employee.

Employers are trying to identify who out of their candidates are capable of doing the work, have the ability to settle into the companies’ culture and to hopefully avoid recruiting an employee that’s causes more problems than they solve.

So, when I’m recruiting, I do not, and will not ask a candidate for their Stack Exchange identity, or their Facebook username, Twitter account or Google ID. I would consider all these as private personal activities, and would respect the candidates’ reasonable expectation that these were not work-related issues, unless by their conduct they made them so.

If on an application, a CV mentioned their Stack Exchange identity, I would ignore it, other than noting that they use Stack Exchange, mildly positive for a graduate, kind of expected for anyone with commercial experience.

My interview process is about giving the opportunity for a candidate to demonstrate that they can do the work we are recruiting for. If they can demonstrate that, and look like a reasonable social mix then they will probably be offered the job.

I could see the Stack Exchange account being used like references, in that job is offered, subject to satisfactory references, but I’m still far from convinced that this is fair, and not undue intrusion into their non-work life.

If as part of an interview process I was asked if I use and contribute on Stack Exchange, the answer would be yes, but if asked for my user name, I would say ‘I’ll have to get back to you on that’. The reason why is this: I have never been employed to contribute to Stack Exchange, and until that changes, it’s completely part of my private, personal life.

Now, consider what the effect would be on Stack Exchange if your profile became part of the interview process.

People would soon learn that you would have to have a pretty exceptional profile for it to be a significant factor in you being invited for interview, and that it’s never going to make up for a bad interview. In short, its only effect will be to prevent you from getting a job.

So, just like you take great care about what goes in your CV, you would do the same on Stack Exchange. No comments, only very carefully thought-out answers, and if you were not 100% sure, you wouldn’t post. Would you leave up a down voted answer? Or badly received questions? Of course not.

Stack Exchange will be the worse for it.

I will typically search for a candidate’s information on Stack Overflow before I conduct the interview. It is public information after all, and then usually during an interview I will ask them what kinds of resources they use to learn something new, or solve a problem that they’re having trouble with. If the person mentions Stack Overflow, bonus points to them, but it’s not necessarily a deal breaker.

Most of my questions are open-ended and revolve around problem-solving and approaches to requirements, and they are never a question that could be answered by reading online documentation, so I’m looking for people who are always learning and exploring.

As for GitHub, I do also ask if they participate in any open-source projects, and if they mention GitHub, I consider that a bonus as well.

I’ve never been asked about Stack Overflow at a job interview. As I’ve used this handle for more than a decade, and some of the politically oriented posts with this handle can be seen as ranging from trotskyist to ayn randist. My politics are none of their business (other than running for elected office, and maybe not even then), and I would not tell them this handle. I’m also winding down use of this nickname and ramping up usage of a different one.

I’m sure I could learn more about a candidate in 5 minutes by looking at the questions and answers they have posted on SE than by a 30 minute interview.

Yes, you could. I’ve been in the workforce for a long time, and I’ve had some bad experiences. Someone interviewing me and checking my posting history might wonder if I’d be posting about them too.

and refuse to accept candidates without a GitHub account

My current employer prohibits contributing to open source projects as they are terrified of having GPL code infecting their codebase.