Article Goals

• Understand the 3 parts of a Resource Key: type, group, and instance
• Learn how to override an existing resource vs creating a new once

Unique References

Resource keys are comprised of 3 numbers, type, group, and instance.

• Type - Acts like a file type.
• Group - Depends on resource, often unused and set to 0.
• Instance - A unique ID

When combined, these three fields are known as a Resource Key and act as a unique identifier for a resource. When writing a key, it is written using hex in the format Type:Group:Instance.

• 0x00B2D882:0x00000000:0x0AD03055DAB19FC7
• 0x015A1849:0x00852CE1:0xC813FB9262F7D81D

Data Types

Q: Why is instance longer than type and group?
A: Numbers can be stored as different types. Instance uses a type with a larger max range. For more details, see data types.

Override vs New Instance Important

Resources Keys determine if a resource will override an existing resource, or create a completely new resource. You override resources by reusing an existing resource key. Let’s look at an example using an image.

Sims 4 icons are DDS images, which use type 0x00B2D882. Icons always use group 0. The Ambitious trait uses instance 0xE9210ACE5B40E587. Thus, adding a DDS image to a package with resource key 0x00B2D882:0x00000000:0xE9210ACE5B40E587 will override the Ambitious trait icon.

This mod overrides the Ambition trait icon.

Likewise, adding a DDS image with with a new instance will create a new resource that can be referenced by modded content. Unique instances are generated using FNV hashing, which will be discussed later.