In Lightning Platform, Salesforce provides multiple options to administrators so that they can grant data access to different users, groups, teams. But there is something which is implemented and maintained by Salesforce which will also give relational data access to users based on their’s access to other records. In Lightning Platform, it is known as Implicit Sharing. Administrator cannot change the way implicit sharing works. So it is very important to understand the different types of implicit sharing we have in the platform.

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In this blog post, I am going to explain different types of Implicit Sharing and how it works.
To understand, let’s first consider the Account and Contact object. These two objects are linked with each other. So let’s say the Organization Wide Default for both Account and Contact are mentioned as Private, i.e. the record owner can see the records they created or owned.

With the above assumptions, here are the different Implicit Sharing we have –

  • Parent Implicit Sharing: This sharing provides read only access to parent record if the user is having access to the child record. Example – Refer the picture below. Here Bob is getting read-only access to Account because he is having access to the Contact (bcoz: Jimmy manually shared the contact with Bob). The level of Account access Bob will get is Read-Only and it is because of Parent Implicit Sharing.
  • Child Implicit Sharing: This sharing provides Read/Write access to child record if the user is the owner of the parent record. Example – Refer the picture below. Here Jimmy is getting read-write access to Contact because he is the owner of the Account record. The level of Contact access Jimmy will get is Read/Write and it is because of Child Implicit Sharing.
  • Portal Implicit Sharing: This sharing will provide Read-Only access to portal account and all associated portal user’s contact record using portal role sharing. Example – Refer the picture below. Here both Ryan and Jimmy are getting Read-Only access to Account because they are portal contacts. This is happening because of Portal Implicit Sharing. But contact Bob is not having any access to Account since he is not enabled as Portal user yet.
  • High Volume Portal Implicit Sharing: In this Implicit sharing any record owned by high volume portal users will be shared with other high volume users who are part of Sharing set.
  • High Volume Parent Implicit Sharing: In this implicit sharing, read only access will be given to parent account of records shared through a sharing set to other user members.
I would recommend going through the below documents to understand how the sharing and record level access is maintained within Salesforce.