In Sweden, church parishes were responsible for maintaining written records of their citizens. This started in the middle of the 18th century.
Nowadays that means there are huge amounts of personal information like births, christenings, weddings, deaths, moves, family constellations, occupations, and so on.
Far from all, but a lot of this information has been digitized and made available free of charge online. Some of it is scanned and cataloged and some of it is scanned, cataloged and indexed.
You can search by names, birth dates, places of living and many other things. In addition to text answers, you often get the scanned documents, many of which are several hundred years old.
Also, in addition to these church records, many other archives have been digitized by the state owned Riksarkivet (the national archive). Military records, travel records, prison records, and so on.
They even made this available in English. Go ahead, find your old ancestors from Sweden:
Best regards, Niklas 🎈