Inspector Guidelines

The following sections are general guidelines that describe fundamental Inspector design principles for Mac applications. Following these guidelines will help you create functional and consistent Inspector implementations that are easy for Mac users to understand and use.

PDX Transit with an Inspector Sidebar displaying metadata for both the selected transit stop and selected arrival.

Table of Contents

• Introduction
• Designing an Inspector
• Inspector Types
• Grouping Content
• HUD-style Panel
• Inspector Minimum and Maximum Widths
• Other Considerations
• Additional Reading

Introduction

Inspectors, whether panels or sidebars, help reduce the clutter of a user interface by placing auxiliary information or controls that can be shown or hidden by the user.

Inspector views are also contextual and dynamic. Depending on the context (what is currently selected or has focus), the content of the inspector is shown, enabled, or completely hidden. The inspector should update its content or what is enabled as soon as the selection or focus changes.

Inspector panels float on top of the app's windows and disappear when the app is deactivated (not at the forefront).

Most Inspector panels use the standard panels UI, which means that they use the same textures in the window body and title bar that a standard window does. Also, an Inspector panel with standard UI must use small versions of the standard UI controls.

In some cases, you may need to use the HUD-style panel, which means that they use a dark, translucent background for the window body and title bar, and they use small white and gray UI elements.

Designing an Inspector

Inspectors often display two types of content:

Inspector Panels showing informational metadata for a selected document and controls for a selected layer in an image editor application.

• Informational details and metadata
  QuickTime’s inspector displays metadata such as resolution, file size, video and audio format, data rate, audio channels, etc.
• Controls to edit or modify selected content
  Xcode has many inspectors in the Inspectors sidebar, including controls to change the attributes of controls in a Storyboard.

Inspector Types

Inspectors can be displayed in two ways:

Your application can display an Inspector as a sidebar or as a Panel.

• Panel Window
  A separate, floating panel window. While this becomes the key window, your application remains the main window. Closes on Esc.
• Sidebar
  The modern way of displaying an inspector. The inspector view slides in from the right side of the window in a sidebar and is part of the main application window.

Grouping Content

Inspector Panels displaying metadata organized in disclosure groups or tabs using a tab view.

Content should be organized into collapsible sections with disclosure buttons, grouped under tabs (using a tab view), or a mixture of both. Sensible organization allows users to easily remember how to get back to a control they may need.

Inspectors, especially those in panel windows, should use the small control size and be organized densely within their view. Inspector panel windows should not take up too much space.

For guidance on creating layouts for Mac apps, refer to the Layout Guidelines page.

HUD-style Panel

An Inspector panel using the HUD style on the left.

In general, use the standard UI for your Inspector panel. For some apps, such as highly visual, immersive, HUD-style Inspector panels are appropriate. The dark translucent background of HUD-style Inspector panels are meant to help minimize distraction in video or image editing applications.

Have a good reason to use a transparent panel instead of a standard panel. Users can be distracted or confused by a transparent panel when there is no logical reason for its presence. In general, you should use transparent panels only when at least one of the following statements is true:

• Your app is media-centric; focused on movies, photos, or slides.
• Users use your app in a dark environment or in an immersion mode (this app is always in Dark Mode or has dark custom UI).
• A standard panel would obscure the content that users need to adjust using the Inspector panel.

Each Inspector panel in your app can have its own style (some standard, some HUD-style), however, always keep it consistent. The same Inspector panel should not switch between styles depending on the state or mode of your application.

Inspector Minimum and Maximum Widths

Whether your inspector is a panel or a sidebar, it needs sensible minimum and maximum width limits. A good starting point is 225-275 pts as a minimum width and 350-400 pts for a maximum width.

Other Considerations

• Inspectors must always include a menu item in your application's menu bar to open them; Sidebar inspectors must have a toggle to show/hide in the toolbar as well.
• If using a tab view in a panel window, the panel’s window title should be the name of the selected tab; Otherwise, the title should simply be “Inspector”.
• Disallow the user from minimizing the panel window by disabling the minimize window control.
• Do not use the word "panel" in your UI labels to show inspector. If it would add clarity, use the word "window" instead. "Show Inspector" or "Show Inspector Window" would suffice.

Additional Reading

• Layout Guidelines: Learn how to design layouts for your Inspector Sidebars or Panels that feel right at home on the Mac.
• Sidebar Guidelines: Since we've touched on sidebars, learn how to design standard navigational sidebars for your Mac app and all the considerations you should take.

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Document Revisions

• Updated June 11, 2026
  Additional information on HUD-style Inspector Panels.
• Published June 7, 2026
  Initial release date.