Recently, while looking for jobs, I found an online advertising company which had a vacancy at a position I was interested in, and I applied for it.

I also run a semi-popular open source project that focuses on blocking online advertising.

Does the above situation create a conflict of interest, and can it affect my career development negatively?

  • 6
    The simply answer is "Yes, of course". Can you explain what you are looking for in an answer beyond the obvious?
    – nvoigt
    Aug 12, 2017 at 11:48
  • 4
    It would show competency but I think you would need to remove yourself from the open source.
    – paparazzo
    Aug 12, 2017 at 13:55
  • That would be an extreme version of a conflict of interest. I refrained several times from open sourcing because of much smaller problems
    – Sascha
    Aug 14, 2017 at 9:17
  • 1
    Not an answer, but I just want to say thank you for contributing to these projects that make browsing the internet bearable ;)
    – Erik
    Aug 15, 2017 at 9:47

4 Answers 4


Well, I think the first question you have to ask is: does it create a conflict of interest within myself? Why would I work for a company creating advertisements which I'm so dedicated on blocking? A good answer would be (but I'm not sure if it applies to you): because I want to create 'good' ads which are relevant, non-obtrusive and not distracting the user. In that case, you create value both for your new employer and for users of your open-source project. Your experience with ads and ad-blockers can even be a unique selling point (compared to other candidates)!

It's certainly something you should bring up during the hiring process (maybe in your application letter, but at the latest during the first interview). If your employers finds out later that you've been involved in writing an ad-blocker (even if you don't contribute actively anymore), that's a sure way to get fired.

  • Someone would actually get fired for this kind of thing you reckon? What country/jurisdiction are you thinking about here? Dec 10, 2018 at 15:49
  • Employment contracts may have a clause that bars the employee from doing work “on the side” (whether paid or not) which leads to a conflict of interest, or require the employee to obtain permission from their employer first. If OP has that kind of contract and develops an ad blocker without seeking permission from their employer, they are violating the terms of their contract, which may entail disciplinary consequences. Even in the EU, where lawmakers tend to side with employees more than they do, say, in the US.
    – user149408
    May 14, 2020 at 20:25

I think you're totally right with the assumption there's a conflict of interest here, both ways. These are generally considered an issue on a career path, "conflict" is never a positive word. I think the fact you write this question shows you already know there's something wrong there.

I see several potential issues which might or not happen, but still:

  • this could show in your job interview that you're mostly against advertising and make you not get the job
  • if you get through and get offered a contract, this kind of activity may be banned from it
  • your fellow open-source "colleagues" might not find it right neither if they ever find out (which may not be possible if you don't tell)
  • your could hardly be really motivated in both at the same time, this will somehow reflect in the motivation you're showing or your performance. In the company, this would most probably cause lack of progress in your career, if not dismissal.

I also see the personal ethics side that could be an issue. But maybe this job is only for the money, and the open-source project for passion, and advertising being all about the money I personally would not care too much. This is however my way of seeing things and others might have a real struggle dealing with that.

  • 1
    @JoeStrazzere I don't think that's an issue; that's how security usually works. You are motivated to beat your own security code, so you can make it better as a result. The issue only comes up when the company wants you to make changes to the ad-blocker itself, to let their ads through.
    – Erik
    Aug 15, 2017 at 9:50
  • 2
    @Erik I get what you mean, but I doubt any boss agrees with it if you actually publicly release the solution to your security you created in his time. Beating your own security otherwise is obviously good.
    – Jeroen
    Aug 15, 2017 at 9:54

I was in a really similar situation (I did a PhD in online privacy, and then went to work at an ad company).

The ad company just appreciated me more for it, because it meant I had a lot of domain knowledge and didn't have to be brought up to speed on stuff. (And anyway most people don't go into ads because they really believe in the product.)

The privacy people I worked with were probably pretty unhappy.

Of course, the ad company would probably not have been happy if I had continued to do privacy research while being employed by them. You should probably quit your open-source project if you take this job, otherwise you risk causing harm to your future company (and they could fire you).


I don't see the conflict. Your interest is developing software. You should be willing to develop any software that doesn't directly conflict with your outside interests. If you have no particularly strong opinions about advertisements, then it's absolutely fine to work on an ad blocker at one time and for an advertisement company at another time.

Now it might have been that you hate advertisements. In that case, you wouldn't have applied for that job, right? If you are asked, you talk about all the interesting things you learned, all the technical challenges you mastered, and how you produced what your customers wanted.

  • I think the situation is a bit different as the OP seems to indicate he would be doing both at the same time, advertising in the day and ad-blocking in the night...
    – Laurent S.
    Aug 14, 2017 at 7:18

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