The owner of a family tree on Ancestry can invite people to participate in researching their family history (see "Sharing a Family Tree"). The invited person will then receive an e-mail from Ancestry which contains a link to the shared tree. If they do not have an Ancestry account they will be asked to register for a free account and the tree will be associated with this new account. Users with an existing Ancestry account will have the shared tree added to their list of available trees. For more details see "Accepting Ancestry Tree Invitations" at Ancestry.
When registering for an Ancestry account, be aware that Ancestry can generate a lot of e-mail. So keep an eye out for the options which let you control how much e-mail Ancestry sends you during the registration process.
Registration with Ancestry is required to allow the tree owner to control the level of access granted to the invited users. Currently Ancestry provides three levels of access:
- Guest: read-only access to the tree, living people are hidden by default
- Contributor: can add some types of content, in particular "stories" and media, living people are hidden by default
- Editor: can edit the tree, living people are visible
Access to a shared tree only requires an Ancestry account, which is free. However access to many of the databases on Ancestry requires a subscription, thus linked records from the databases may not be visible or may have limited access to users without a subscription. Given that most public libraries and archives have an institutional subscription, users who do not want to subscribe can use these institutions to see this additional information.