Using mySIMBL for Deep macOS Customization

mySIMBL is a utility for installing application bundles in . These packages can deeply customize your macOS experience, providing toggle switches for hidden values and exposing new functionality. It's not the most stable tool, but it provides opportunities for macOS that are otherwise inaccessible.

What Is SIMBL?

SIMBL (a.k.a. Simple Bundle Loader and Smart Input Manager Bundle Loader) is the basis for mySIMBL. It allows developers to make modifications to programs written in Cocoa without access to the source code. Originally, SIMBL was used to modify Apple's Safari browser (once known as PithHelmet), which didn't have an extension infrastructure until 2010. Today, SIMBL is a platform for modifying how programs run on your Mac. It can inject changes into other applications, allowing you to change how applications look and run. Fundamentally, you can imagine SIMBL as a package manager for application plug-ins.

Installing mySIMBL on macOS

By itself, mySIMBL is only a framework for managing plugins. By itself, it doesn't change any functionality, but it provides the tool that allows you to install plugins.

To install mySIMBL, download the application from the project's GitHub page.

Then, either drag it to your Applications folder, or use the pop-up options to move the application there on first run.

Downloading Bundles for macOS Customization

Bundles can be accessed and installed from within the mySIMBL application.

1. Click on “Discover” in the menu bar on the left of the mySIMBL application.

Mysimbl Discover Sidebar

2. Use the search box in the upper-right to filter all applications by name.

Mysimbl Search For Packages

3. When you've found a plugin to install, double-click on the plugin's row.

4. Click the “Get” button to install the selected plugin.

Mysimbl Get Button

5. When the application is installed, the “Get” button will change to “Open.”

6. Once the application is involved, you will need to restart the target application. Applications that affect the entire system may require you to reboot your Mac. Other applications may not even require a restart.

Uninstalling and Deactivating Packages

To deactivate a package, click on the green dot at the right of its menu item in the “Manage” screen.

Mysimbl Deactivate Plugin

If you want to uninstall a package, first find it in the Discover screen. Click the plugin bundle to open its detail screen, then click the “Remove” button to uninstall the plugin.

Mysimbl Remove Plugin


mySIMBL is far from a perfect application. They haven't yet reached a 1.0 release, meaning that the application is still considered to be in beta at the very least. That said, the infrastructure provided by mySIMBL enables system and application customizations that wouldn't otherwise be possible. For example, there's no way to “float” application windows on top of all application windows without the mySIMBL plugin Afloat. So, for some users, the trade-off in stability will be worth the extended capabilities.

The one thing mySIMBL doesn't offer is much control over bundles. At the moment, there isn't much a user can do to control a plugin bundle after its been downloaded. It either does its thing, or it doesn't. Future versions of mySIMBL may provide this feature, but for now, users are limited to the functionality provided by the plugin without user interaction.

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