People conceived from donor eggs and sperm will be able to contact their biological parents with the launch of a new register.
Donors could give up their anonymity
Where both parties agree, the UK DonorLink register will bring together parents and adult children.
The agency running the project pledged confidentiality would not be broken without permission.
The government said the aim was to bring rules for the donor-conceived in line with those for adopted people.
The exchange of information will cover people conceived through donated eggs and sperm, their donor parents and half-siblings.
The information given could include identities and addresses if both parties want it, but otherwise could be limited to details such as age, job, interests and whether the donors have other children.
Both parties will be able to meet if they want to.
The government has separately agreed to end sperm donor anonymity from next year, which will take effect when the first children conceived in this way reach 18 in 2023.
A BBC survey asked UK clinics about the implications for them of changes in the law.
It found that 48% of clinics which recruit donors directly say they have low sperm stocks. And 65% do not feel confident about finding donors in the future.
The new register applies to donor-conceived people aged over 18 and people who donated in the UK prior to the Human Fertilisation and Embryology Act coming into effect in 1991.
UK DonorLink is now asking the Department of Health to address the issue of people who donated from 1991 onwards.
Lyndsey Marshall, manager of the register, said: "There is no intention to track people down against their expressed wishes.
"Indeed information can be exchanged without revealing the identity of either party, if desired.
"However, we know that there are many people out there for whom the provision of such information will enable them to get on with their lives with fuller knowledge of their backgrounds."
The Department of Health has so far provided £160,000 of funding for the register.
Public health minister Melanie Johnson said: "This is an early part of our commitment to aligning the position of donor-conceived people with that of adopted people.
"It is important that donor-conceived people are given the opportunity to access information about their genetic origins and UK DonorLink will provide a forum for voluntary exchange of information via DNA testing."
Laura Spoelstra, chair of the National Gamete Donation Trust, welcomed the register.
She said the numbers of donors and children coming forward under it would give some indication of how many people will continue with donations once next year's law change comes into effect.
She said: "What we think is needed now is a general awareness campaign on the new laws saying, 'There is a chance you will be contacted in 20 years' time, would you still be prepared to donate?'"
One sperm donor said he would not donate again once anonymity was no longer guaranteed.
He said: "I thought I was helping people, but to have that thrown back in my face, to have children coming to find me years down the line, I couldn't handle that."