InjectJS

InjectJS is an open source Safari extension that lets you save and run arbitrary bits of JavaScript code for the websites you visit (aka userscripts). It implements a Javascript editor right in your browser for a simple method of creating and saving your code.

Features:

- Open source
- Simple usage
- Automatically locally saves your script to the file system
- "Advanced" Javascript editor with auto complete
- No user tracking

Use cases:

- Automatic page redirection
- Website page manipulation (styling, element creation)
- Custom ad-blocking
- Website custom code injection

If you're looking for a way to easily create quality of life Javacript code snippets for your web browsing experience, give InjectJS a try.