If you have an offer of full-time employment, it's relatively easy (especially in the technology sector, since "in-demand" areas have some extra deference). This is sometimes called "sponsorship", but unlike the U.S. H1B process, the company doesn't really have to do anything besides offering you a job. But, it's not easy to move there without a job offer.
It is pretty easy to do get a job offer in our industry.
And employers know that the visa/work permit process is easy, quick (typically a few weeks) and predictable, so there is a lot less bias against foreign applicants than in e.g. the US.
Yeah, I agree it's pretty easy if you want to move to Sweden to work at a tech job. But I think it's a reasonable caveat; some people might want to move to Sweden for other reasons, like starting a company or as a base of operations for freelancing, and that's considerably harder.
IMO Scandinavia is actually a great place to be a freelancer, even for foreigners, if you can build a modest network. High cost of living, but no worry about health/benefits being tied to your job, very English-friendly, and a lot of part-time/freelance tech work that pays well. But it's very hard to get the formalities sorted out for that, unless you first get an EU citizenship or permanent residency via another route.
Can someone on a visa switch jobs? In the U.S. changing jobs while on a visa resets the residency process, which indentures the employee to the employer.
For the first year, you're tied to your employer. After that, you're free to change jobs, but only within your field of work.
You need to reapply for the work permit when you change jobs or every two years (max validity duration), which is quite painless. After 4 years you should get permanent residence, and no longer need any permits.. This is the process for most non-EU residents.
It's (for now, anyway) a fairly routine process. If you've been a legal, self-sufficient resident of Sweden for 4 years, you get permanent residency after a straightforward application.
There is some debate over adding a Swedish-language requirement, but there isn't currently one. That is one of the two difference with Denmark: if you're a non-EU immigrant to Denmark, you need to live there 5 years under the same conditions rather than 4, plus pass a middle-level Danish competency exam.
Unfortunately, considerably harder. There is a visa category (in Denmark, also, which I'm somewhat more familiar with), but it's not anything close to the almost-a-rubber-stamp process that the pending employment offers category is. Things will go most smoothly if you have venture capital or revenues already, and you want to move the business there.
There is considerable general interest in startups, and people talk about doing something to make it easier to get a visa to start a company. But there are still some roadblocks preventing a more streamlined process. One is that people aren't sure how to judge a legitimate startup, from any random person who claims to be "doing a startup". And there's even some paranoia that your "startup", if not fake, is a real but unsavory business, perhaps some kind of import/export business involving the trade in smokeable plants. Another purely political-coalition-based factor is that the streamlined employment visa categories were pushed through (over some nativist opposition) by big businesses with hiring problems, and so they are narrowly tailored to solve their problem, which is how to get their own new hires into the country with minimal expense/delay.
edit: parent comment was asking about a visa to start a business in Sweden. I think the above might be useful information, so I'm leaving it anyway.
