Before searching an ancestor on this forum, please try this web site, the largest, the biggest and the only one with an interface in english and other languages;
Only constraint: register (free) to get results but tool is powerfull.
also refers to databases due to ocr software = if an ancestor is quoted in the nal library document, you will see him appear.
Most of names come from individual search (family trees), some from perusals (payment access required)
Of course, non standard cases: Alsace Lorraine (lots of people became german or french in 2 centuries before their long journey to America (after 1848 & 1870) so they are present either as french or as German. "Give me your poors..."
Search is only by name and location.
Search by first name and family name is a payment access. Remember: some have (I did!) subscribed only for your help.
For search of Eastern Europe Drama (russian revolution, jewish people escape)source is different.