Building in public vs hiding it from your employer?

Personally I wouldn't be worried about what your co-workers think. I would be concerned about what HR, legal, and your boss might think or do. That's certainly worthy of your consideration and debate.

I think you need to make sure there are no conflicts of interests. If you feel comfortable, you might even broach the subject with your boss depending on the nature of your relationship.

I would also make sure there is no inventions agreement in place that would assign the ownership of anything you build to your employer. That could certainly cause some issues. In the case of an inventions agreement, it doesn't matter if you do it on your own time or you didn't use your employer's equipment. Some of these agreements are so broad that it doesn't even matter if it's related to what your employer does or not.

I know because I've signed several of them over my career and consulted with an employment lawyer when I left my last job. When in doubt, always get a legal opinion...

It really depends on the culture at your work place on how you want to handle this. As others have already said you want to make sure you are fine legally, with HR and your boss more than worrying about what your co-workers think.

Assuming everything is okay for you to be working on it, some companies actually prefer employees doing things on the side as long as its not interfering with or competing with your work there. I've worked at several places where they were glad to have employees working on things outside of work, especially if it was related to the field, as they viewed it as additional training and practice. It was a bonus to be practicing our craft to the employer as it made us better workers and more valuable to the company.

Not sure whether you’re just hacking for fun or planning to incorporate a side business, but if the latter you may not have a choice. One of the requirements in my Stripe Atlas LLC legal paperwork was that I notify anyone else with whom I was employed.

I see most of replies saying don't worry if it's not on companies time. But they are ignoring your point. You're absolutely right! If your boss slacks you expecting you to put in crunch time, late evenings or weekends and you don't. Or some project is running late due to no fault of your own, perhaps it was under estimated, feature creep. IF folks see you talking about spending time and coding and working on your own thing, they might really wonder why you're not putting it towards the company. If you feel like this, then it's best to trust your intuition. Or build under a pseudonym.

Depends on who your employer is and what are you building. There may be conflict of interest, for example. If you start building something you may be less eligible for promotion. Or, as you mention, you may face backslash from your colleagues (regardless of whether it is justified or not). There may be also some concerns regarding IP rights (not sure what are you building).

From the outside, it is impossible to say, you'll need to judge how the work environment is. One valid question would be what is your motivation to build in public. If it is not large enough, then don't do it and play it safe. In my case I was always in positions of great flexibility, even encouraged to write publicly about the things I was doing, and that's what I am passing down to the people I work with now a days.

If you are not doing it on your employer's time using your employer's resources, then I don't think you have anything to worry about. Particularly, if your performance at you day job is not suffering (perhaps due to not getting enough sleep the night before because you were working on your side project). ALl the best!

I don’t think that should be a problem. Most of people don’t even care, imagine going and telling their bosses. But if you’re fearful of that, why you don’t create also a side account. Might be the official account of your Side project.