Honestly, depends on the company and the state you're working in. It's all anecdotal, so take the following with a grain of salt.
I've worked for startups in Washington and California. In Washington, there was an invention clause in my contracts, but in practice it was a) practically unenforceable and b) as long as you divorced your work identity from your personal identity, nobody cared. This meant not having a way of tracing an anonymous handle or email to you working for the company. In California, I've never seen an invention clause in my contracts, but they were also much better at divorcing your work and personal identity systematically (forcing you to use a github account specific to the company, not mentioning this handle on your personal account, etc.).
In any case, keeping your work and personal work completely separate (no competition between work and individual ideas, no shared hardware) is a good idea and won't raise as many eyebrows. Some companies will be more aggressive about owning what you do, so if it matters to you then ask about the clause before signing the contract.
> In California, I've never seen an invention clause in my contracts, but they were also much better at divorcing your work and personal identity systematically (forcing you to use a github account specific to the company, not mentioning this handle on your personal account, etc.).
California has a state law that covers this. Any work you do on your own time, with your own resources (so, not your company laptop or photocopier) is your own and the company cannot force you to assign it - so long as the work is not connected to your employers current or reasonably anticipated business.
In practice, though, even in CA, I would suggest employees always get something from their company, in writing, disclaiming any ownership of any project they decide to start or work on (in any large capacity), especially if it's a software project and they work for a software company.
Even if you truly believe what you're working on has nothing to do with your employer's line of business, they may disagree, and even if they're wrong, they can make your life difficult and expensive while you try to prove them wrong.
It makes me sad that this is a thing I feel I need to suggest, but I think it's the prudent move, and many companies will even have a fairly painless, well-defined process for doing this.
That's a great call-out, and one that's particularly relevant when you work at bigger companies. For instance, what can you confidently say isn't part of Apple's reasonably anticipated future business?
as a young developer in California Silicon Valley area, I saw companies try to create 24-7 blanket enforcement of IP rights, solely to increase control and profits; I also saw coders definitely steal company IP and try to start new companies. That State law you are referring to was passed long after this battle was underway, and I can tell you that companies definitely denied that the law existed, said it was unfair, and also paid lawyers to write contracts that tried to take employee IP anyway, and use sales tactics on new employees to accept it.
I've worked for startups in Washington and California. In Washington, there was an invention clause in my contracts, but in practice it was a) practically unenforceable and b) as long as you divorced your work identity from your personal identity, nobody cared. This meant not having a way of tracing an anonymous handle or email to you working for the company. In California, I've never seen an invention clause in my contracts, but they were also much better at divorcing your work and personal identity systematically (forcing you to use a github account specific to the company, not mentioning this handle on your personal account, etc.).
In any case, keeping your work and personal work completely separate (no competition between work and individual ideas, no shared hardware) is a good idea and won't raise as many eyebrows. Some companies will be more aggressive about owning what you do, so if it matters to you then ask about the clause before signing the contract.