Those who have installed mods for GTA 5 may have used a tool named Script Hook V for the same at some point.

Script Hook V Script Hook V is the main program you'll be using to run Grand Theft Auto 5 mods. It lets you install and run .ASI mods — the most common type — and also includes a sample mod ...

The Script Hook V is one of the most popular GTA 5 mods that PC players often use in their games. It is an offline mod that you can only use in Grand Theft Auto 5 Story Mode.