The Welsh language needs to be "normalised" online, say campaigners.
Heledd Gwyndaf, of Cymdeithas yr Iaith, the Welsh language society, said it was the "eleventh hour" for Welsh on digital platforms.
She said increasing online content was as important as the translation of the Bible into Welsh and the development of the printing press.
The campaign group wants to launch a movement that would help promote and produce online content.
Ms Gwyndaf, who chairs the society's digital group, said young people's online habits made it a pivotal moment for the language.
"If we want the Welsh language to live, this could be its eleventh hour," she warned at the National Eisteddfod in Llanrwst.
Young people are increasingly turning to sites like YouTube and watching only English language content, she added.
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"We must look at what's happening there [online], what isn't happening there, and what is the solution to ensuring that Welsh language content is seen by our children and our young people, and people of every age."
According to Cymdeithas yr Iaith, the new digital initiative would:
- research the accessibility of existing Welsh language content, the demand and the ability to create content
- create and support new platforms to increase the presence of Welsh online
- improve awareness among individuals, groups and organisations of what is available and what is to come.
'Older people too'
In another event, organised by the Welsh language movement Dyfodol i'r Iaith, the chief executive of S4C, Owen Evans, said digital content needed to appeal to a broad audience.
Speaking afterwards, Mr Evans said: "I think digital is for everyone.
"Digital services are for older people too - older than me, even - who want to watch it, and the number of people consuming digital content is growing and growing."
He said the traditional channel was still very important for S4C's audience, but more co-productions crossing between the TV channel and its digital platforms would be broadcast in future.
"The challenge for S4C is to bring the two together."