Clarification in case any H1B holders are reading: you absolutely can transfer your H1B visa, though I think a break of more than 30 days would be a violation.
The trick is when you H1B employer also offers to sponsor your green card. That isn't transferrable, and if you're from certain countries (like India) it can take up to ten years to get one.
> "The trick is when you H1B employer also offers to sponsor your green card. That isn't transferrable"
Yes but the priority date itself is transferable. This allows you to job hop as many times as you want, without losing your place in line. If you have to wait 10 years for your green card, you might as well take advantage of this option and only worry about your green card 9 years down the road.
You don't lose your priority date if you get a promotion within the same job role. Eg, you can go from entry-level developer to senior-staff developer, without any issues. Google senior-staff developers make over half-a-million, so that's quite a high ceiling. I even know someone who made the switch from hardware-engineering to software, and kept his priority date.
The trick is when you H1B employer also offers to sponsor your green card. That isn't transferrable, and if you're from certain countries (like India) it can take up to ten years to get one.