Aqua (user interface)
Aqua is a graphical user interface, design language and visual theme used in Apple Inc.'s operating systems. It was themed to replicate water, with "droplet-like" components and a heavy use of reflective effects and translucency. Its goal was to "incorporate color, depth, and complex textures into a visually appealing interface" in macOS applications. At its introduction, Steve Jobs noted that "... it's liquid, one of the design goals was when you saw it you wanted to lick it".
Aqua was introduced at the 2000 Macworld conference in San Francisco. It was first released in July with iMovie 2, and with Mac OS X 10.0 the following year. Aqua is the successor to Platinum, which was used in Mac OS 8, Mac OS 9, and developer releases of Rhapsody. Apple continually revised Aqua with subsequent operating system revisions, including adding SwiftUI design standards and Swift language support into Aqua’s interface, and implementing its design into newer products such as the iPhone. In 2013, Apple heavily revised the skeuomorphic user interface to adopt a flat design. In 2025, Apple introduced the Liquid Glass design language across their operating systems, which was heavily inspired by older iterations of Aqua.
Background
For years, Apple had been trying and failing to produce a next-generation Mac OS operating system, including projects code-named Pink, Taligent, and Copland. Mac OS X was ultimately built on NeXTSTEP, after Apple purchased NeXT and its CEO, Steve Jobs, returned to Apple, the company he had cofounded.Early versions of Mac OS X, called Rhapsody, was a developer release that had an interim user interface, blending MacOS 8's "Platinum" and OpenStep looks. The Rhapsody approach was ultimately abandoned, and the new operating system was dubbed Mac OS X in 1998. Early developer previews of Mac OS X shipped with an interface similar to Rhapsody, combining classic Mac OS and NextStep. The final operating system interface, Aqua, would be unveiled at Macworld Expo in January 2000.
Design elements
Aqua uses blue, white, and gray as the principal colors throughout its style. Window toolbars, window backgrounds, buttons, menus and other interface elements are all found in either of these colors. For instance, toolbars and sidebars are often grey or metal-colored, window backgrounds and popup menus are white and buttons are accented with a bright blue. In versions of prior to OS X Yosemite, most controls have a "glass" or "gel" effect applied to them. David Pogue described this effect as "lickable globs of Crest Berrylicious Toothpaste Gel".macOS has few native customization options to change the overall look of the system. Users can choose a graphite appearance instead of the default blue one. When using the graphite appearance, controls have a slate-like, grey-blue or grey color, including the primary window controls which are red, yellow and green with the default appearance. The appearance option was added at the behest of developers and users who found the blue appearance garish or unprofessional. Yosemite added a dark mode that darkens the predominantly white menubar and Dock. Users can also freely choose a highlight color for text and file selection.
Interface elements
Windows
Historically, Aqua had two window designs: the default Aqua windows and "brushed metal" windows. Aqua windows typically have a metal-like or gray titlebar with three buttons on the left side. Visually, these buttons used to be placed on top, but later appeared 'sunken' into the window. Aqua windows have almost no frame or outside border, instead drop shadows are used to separate and distinguish active from inactive windows. The aesthetic of the window backgrounds changed from pin-striped to white backgrounds. Brushed-metal windows had a thick frame with a metallic texture or dark-gray background and sunken buttons and inner frames. They had the additional property of being draggable at every point of the frame instead of just the titlebar and toolbar. Apple recommended brushed-metal windows for applications that mimic real-world devices or are used to interface with such devices, but was criticised by designers for not following its own guidelines or applying it inconsistently. Brushed-metal windows have been largely phased out since Leopard and become visually indistinctive from Aqua windows.In addition to titlebars, windows can also have toolbars with separate buttons. Up to Leopard, toolbars were visually separated from the titlebar and had the same background as the window frame or were pin-striped. Leopard introduced a unified style that extended the metal-like background of the titlebar to the toolbar, making it appear as one whole. Optionally, a separator could be placed between the titlebar and the toolbar to mimic the previous style. OS X Yosemite brought a compacter version of the toolbar that fused the titlebar and toolbar together, made it shorter and removed the window title.
Drawers are accessory sidebar views that can slide out from any edge of a window except the top edge. They can be resized perpendicular to their window edge but follow the window's size in the other direction. Drawers were once frequently used to display controls and information that did not need to be always visible, but Apple now recommends against their use.
Sheets are dialog boxes that are modal to a specific window. When opened, they are thrust towards the user like a sheet of paper, hence the name. They are partially transparent and focus attention on the content of the sheet. The parent window's controls are disabled until the sheet is dismissed, but the user is able to continue work in other windows while the sheet is open.
Menus
Menus are backed with a slightly translucent solid gray, and when menu items are highlighted they appear blue. In application menus, which run in a single bar across the top of the screen, keyboard shortcuts appear to the right-hand side of the menu whilst the actual menu item is on the left. In Yosemite, the menus are much more translucent and have a blur effect.Drop down menus for use in windows themselves are also available in several varieties. The standard "pop up" menu is white with a blue end cap with opposing arrows, whilst 'pull down' menus only have one downward facing arrow in the end cap. 'Pull down' menus are available in four different Aqua varieties, most of which have fallen into disuse in later macOS releases.
Text boxes and fields
Text boxes are black on white text with a sunken effect border. In addition to regular square text boxes, rounded search text boxes are available. For more extensive text requirements, there is also a multi-line text field. A combined text box and pull down menu is available, which allows the user to type in a value in addition to choosing from a menu. There is also a combination textbox and picker control, which allows the user to type in a date and time or edit it with directional buttons. Mac OS X 10.4 introduced a new interface element that allows the user to drag non-editable 'tokens' to a text box, between which text can be typed. Whitespace before and after the tokens is trimmed.Push buttons
Standard push buttons with rounded corners are available in two varieties: white and blue. A blue button is the default action, and in OS releases prior to Yosemite, would appear to pulse to prompt the user to carry out that action. The action of a blue button can usually also be invoked with the return key. White buttons are usually associated with all other actions.Also available are rounded bevel buttons, designed to hold an icon; standard square buttons; glass square buttons and round buttons. In addition, circular, purple online help buttons are available which display help relative to the current task when clicked. Disclosure triangles, although technically buttons, allow views of controls to be shown and hidden to preserve space.
Checkboxes and radio buttons
In macOS, empty check boxes are small, white rounded rectangles. When they are checked, they turn blue and a checkmark is present. They are essentially buttons which can be toggled on or off. Radio buttons are similar in appearance and behaviour except that they are circular and contain a dot instead of a check. Radio buttons are classed into groups of which only one can be activated at a time.In Yosemite, a short animation was added to show the checkbox or radio button filling in.
Tables and lists
Tables and lists can be broadly categorised in three ways: A standard multi-columnar table with space to enter values or place other interface elements such as buttons; An outline view that can contain disclosure triangles to show and hide sets of data; and a Miller columns view akin to the column view in the Finder. All table views can use alternating blue and white row backgrounds.Progress indicators
Two main types of loading/saving progress indicator are available: a progress bar or a monochromatic spinning wheel. The progress bar itself is available in two varieties: indeterminate, which simply shows diagonal blue and white stripes in animation with no measure of progress; or determinate, which shows a blue pulsing bar against a white background proportional to the percentage of a task completed. The spinning wheel indicator, also found in the Mac OS X startup screen since version 10.2, is simply a series of 12 increasingly darker grey lines arranged circularly, like the side view of a spoked wheel rotating clockwise. Many other interfaces have adopted this device, including the Firefox and Camino web browsers and many Web 2.0-influenced web sites.In Yosemite, the progress bar was changed to a thin, light gray. The "indeterminate" variation kept the pulses, but slower and spaced out. A progress indicator now appears during boot, replacing the spinning wheel indicator found in earlier versions.