The website containing Catholic parish records going back 300 years has had nearly four million page views since it launched.
The National Library of Ireland (NLI) digitised 370,000 images of microfilm reels on which parish registers were recorded. They are accessible free of charge.
The records were put on line in July and so far there have been 255,067 unique users, with the majority from outside Ireland, mostly from the United States and United Kingdom.
Previously, anyone seeking information about their Irish ancestry had to go to the National Library on Kildare Street in Dublin and view the microfilm.
The average length of time spent on the site is nearly 10 minutes, which is a high level of engagement for visitors online.
NLI director Sandra Collins said the digitised records have resonated with the Irish diaspora.
“It is tapping into what it means to be Irish,” she said.
The parish register records are considered the most important source of information on Irish family history before the 1901 census.
Dating from the 1740s to the 1880s, they cover 1,086 parishes throughout the island of Ireland and consist primarily of baptismal and marriage records.
They are valuable because there are no pre-1901 census records. All of these were destroyed except for the 1821 and 1831 records for a few counties.
The NLI has been working to digitise the microfilm for more than three years under what is described as its most ambitious digitisation programme to date.
Minister for Arts, Heritage and the Gaeltacht Heather Humphreys described the number of people logging on to the site as "absolutely amazing".
A lot of work, she said, was put into getting it online.
“The records are a huge draw in getting people to come to this country and trace their roots,” the Minister said.
About 95 per cent of parishes submitted their registries for microfilming during the 1950s and 1960s.
However, 56 parishes were either omitted from the process or did not come into existence until after the cut-off point for records in 1880.
Where this is the case, users are advised to contact the parish in question directly for missing information.