Both sharing rules and manual sharing are ways to extend record access beyond the baseline set by organization-wide defaults (OWD) and role hierarchies in Salesforce, but they differ significantly in how they work and when to use them.
Sharing Rules
Purpose: Sharing rules are designed to automate record sharing based on criteria or ownership.
Scope: They apply to groups of users, roles, or territories.
Automation: Sharing rules automatically grant access to records that meet certain conditions or are owned by certain users.
Use Case: Ideal when you want to share records broadly and consistently, such as sharing all "Open" cases with a support team or all candidate records owned by recruiters with their managers.
Access Levels: You can grant either Read-Only or Read/Write access.
Setup: Created and managed by administrators in Setup.
Example: Share all opportunities owned by the sales team with the sales managers role.
Manual Sharing
Purpose: Manual sharing allows record owners or users with appropriate permissions to share individual records with specific users or groups.
Scope: It is record-specific and user-initiated.
Automation: Manual sharing is a one-off, manual action done on a per-record basis.
Use Case: Useful when you need to share a particular record with someone outside the usual sharing rules, such as giving a temporary collaborator access to a single account.
Access Levels: Can grant Read-Only or Read/Write access.
Setup: Done by users on the record’s sharing button or related list (if enabled).
Example: A sales rep manually shares a single opportunity with a colleague who is helping on that deal.
When to Use Which?
Use sharing rules when you want to consistently share records with a group based on ownership or record criteria.
Use manual sharing when you need to share a specific record with a user or group outside of the normal sharing model, especially for temporary or exceptional access.