CSS Variables

Ionic components are built with CSS Variables for easy customization of an application. CSS variables allow a value to be stored in one place, then referenced in multiple other places. They also make it possible to change CSS dynamically at runtime (which previously required a CSS preprocessor). CSS variables make it easier than ever to override Ionic components to match a brand or theme.

Setting Values#

Global Variables#

CSS variables can be set globally in an application in the :root selector. They can also be applied only for a specific mode. See Ionic Variables for more information on the global variables Ionic provides.

When using the Ionic CLI to start an Angular project, the src/theme/variables.scss file is created where you can override the default Ionic Variables.

/* Set variables for all modes */
:root {
  /* Set the background of the entire app */
  --ion-background-color: #ff3700;

  /* Set the font family of the entire app */
  --ion-font-family: -apple-system, BlinkMacSystemFont, 'Helvetica Neue',
    'Roboto', sans-serif;
}

/* Set text color of the entire app for iOS only */
.ios {
  --ion-text-color: #000;
}

/* Set text color of the entire app for Material Design only */
.md {
  --ion-text-color: #222;
}

Component Variables#

To set a CSS variable for a specific component, add the variable inside of its selector. See Ionic Variables for more information on the component-level variables Ionic provides.

/* Set the color on all ion-button elements */
ion-button {
  --color: #222;
}

/* Set the background on an ion-button with the .fancy-button class */
.fancy-button {
  --background: #00ff00;
}

Variables set via JavaScript#

CSS variables can also be changed via JavaScript using setProperty():

const el = document.querySelector('.fancy-button');
el.style.setProperty('--background', '#36454f');

Getting Values#

Using CSS#

The var() CSS function can be used to get the value of a CSS variable, along with any number of fallback values, if desired. In the below example, the --background property will be set to the value of the --charcoal variable, if defined, and if not it will use #36454f.

.fancy-button {
  --background: var(--charcoal, #36454f);
}

Using JavaScript#

The value of a CSS variable can be read in JavaScript using getPropertyValue():

const el = document.querySelector('.fancy-button');
const color = el.style.getPropertyValue('--charcoal');

Ionic Variables#

Component Variables#

Ionic provides variables that exist at the component level, such as --background and --color. For a list of the custom properties a component accepts, view the CSS Custom Properties section of its API reference. For example, see the Button CSS Custom Properties.

Global Variables#

There are several global variables that Ionic provides in order to make theming an entire application easier. For more information, see Colors, Themes and Advanced Theming.