The most reliable source for all Salesforce-specific iconography is the Lightning Design System (SLDS) . This is the backbone of the Salesforce user interface, providing a consistent visual language across all clouds and apps.
: Developers can browse and preview icons directly in the Lightning Icon Component Reference to see how they will render in code. Top Community & Third-Party Resources salesforce icons download
Before you download, it’s helpful to know which "family" of icons you need for your specific use case: Icons · Lightning Design System 2 salesforce icons download