The National Library of Wales in Aberystwyth can now store web pages and e-mails alongside books in its archive - but has a massive task ahead.
There are 2.96 million websites with .uk in their domain name
It says trawling through millions of UK websites for topics of Welsh or Celtic interest would be made easier by providing those websites with their own identity - like .cym or .wal
But the Welsh assembly has no say over the awarding of country domain names which is governed by a corporation in the US.
The mushrooming of web-based publishing and articles transmitted by e-mail has led to changes in a law passed nearly a century ago.
The Legal Deposit Libraries Act 2003 passed last month- also ensures that electronic publications - like CD-Roms and DVDs can be deposited at the National Library.
The law allows the institution to selectively harvest information from the 2.96 million websites with a .uk suffix.
"We concentrate on collecting publications of Welsh and Celtic interest so it is a huge task to study all the available websites," said a spokesman.
"As there is no .cym or .wal it is more difficult to analyse what is Welsh among these websites."
A Welsh assembly spokesman said deciding which countries were allocated domain names fell to American-based Internet Corporation for Assigned Names and Numbers (ICANN).
"Their policy seems to be to assign suffixes to regions that are members of the United Nations," he added.
Nevertheless, The Isle of Man (.im), Gibraltar(.gi), and Guernsey(.gg) all have their own domains.
Since 1911 Aberystwyth and the five other libraries in the UK have been able to collect copies of all printed material published here.
But material published in electronic and other non-print formats fell outside the scope of the law
That was until the most recent changes, which have been welcomed by Welsh Culture Minister Alun Pugh: "We are delighted the way has been paved for the National Library of Wales to secure a vital part of the published heritage of Wales."
Other archives are held are held at the National Library of Scotland, the British Library, and libraries at the universities of Cambridge, Oxford and Trinity, Dublin.