In US it is at-will employment. What would be the difference really between a trial period and just letting an employee go 2 months or 4 months of 7.83 months down the road. I mean, in at-will employment trial period sounds just like an artificial gimmick that the employer forces onto the employee's mental state.
At-will (or not) employment is only relevant in the absence of a contract. Most/all tech employment has contracts with terms of dismissal. And in my experience this is generally a good thing for everybody. I've lived/worked in countries with for-cause employment and it's overwhelmingly more common for it to be used for abuse than protection - somebody gets fired for very good reason, but then sues just because it's generally cheaper/quicker/better PR to settle than litigate. Montana probably has the best idea of a global probation - 12 months at will, and then the employee can only be dismissed for cause after that.