The web development landscape just got a major upgrade! The CSS if() function provides a concise way to express conditional values, and it’s now available in Chrome 137, which rolled out in May 2025. This groundbreaking feature brings true conditional logic directly into CSS, eliminating the need for complex workarounds and JavaScript interventions in many scenarios.
What is the CSS if Function?
The if() function allows you to conditionally apply styles based on a given condition, making it easier to write responsive and adaptive designs. Think of it as bringing JavaScript-like conditional statements directly into your stylesheets.
Basic Syntax
The syntax follows an intuitive pattern:
property: if(
condition: value-if-true;
else: default-value;
);
You can also chain multiple conditions:
property: if(
style(condition1): value1;
style(condition2): value2;
else: default-value;
);
How It Works
The function evaluates each condition sequentially and returns the value associated with the first true condition. If none of the conditions evaluate to true, the function returns an empty token stream.
The most common way to use if() is with style queries – checking the value of CSS custom properties (variables) to determine which styles to apply.
1. Basic Light/Dark Theme Toggle
div {
color: var(--color);
background-color: if(style(--color: white): black; else: pink);
}
.dark {
--color: black;
}
.light {
--color: white;
}
In this example, if the --color variable is set to white, the background becomes black. Otherwise, it defaults to pink.
2. Component State Management
<div class="status-card" data-status="pending">Pending Task</div>
<div class="status-card" data-status="complete">Completed Task</div>
<div class="status-card" data-status="error">Error Task</div>
.status-card {
--status: attr(data-status);
border: 2px solid if(
style(--status: complete): green;
style(--status: error): red;
style(--status: pending): orange;
else: gray;
);
background-color: if(
style(--status: complete): #e8f5e8;
style(--status: error): #ffe8e8;
style(--status: pending): #fff3e0;
else: #f5f5f5;
);
}
3. Responsive Grid Layouts
.grid-container {
--columns: 1; /* Default for mobile */
display: grid;
grid-template-columns: if(
style(--columns: 3): repeat(3, 1fr);
style(--columns: 2): repeat(2, 1fr);
else: 1fr;
);
gap: if(
style(--columns: 3): 2rem;
style(--columns: 2): 1.5rem;
else: 1rem;
);
}
@media (min-width: 768px) {
.grid-container {
--columns: 2;
}
}
@media (min-width: 1024px) {
.grid-container {
--columns: 3;
}
}
4. Advanced Button Variants
.button {
--variant: primary; /* Default variant */
--size: medium; /* Default size */
padding: if(
style(--size: small): 0.5rem 1rem;
style(--size: large): 1rem 2rem;
else: 0.75rem 1.5rem; /* medium */
);
background-color: if(
style(--variant: success): #10b981;
style(--variant: danger): #ef4444;
style(--variant: warning): #f59e0b;
else: #3b82f6; /* primary */
);
font-size: if(
style(--size: small): 0.875rem;
style(--size: large): 1.125rem;
else: 1rem; /* medium */
);
}
/* Usage */
.button-success-large {
--variant: success;
--size: large;
}
Why This Matters
Before CSS if()
Previously, achieving conditional styling required:
- Multiple CSS classes with lots of specificity battles
- CSS preprocessors like Sass with compile-time conditions
- JavaScript to dynamically add/remove classes
- Complex CSS tricks using calc() and custom properties
After CSS if()
Now you can:
- ✅ Write cleaner, more maintainable component styles
- ✅ Reduce JavaScript dependency for styling logic
- ✅ Create more flexible design systems
- ✅ Eliminate class proliferation for variants
Relationship with Style Queries
Style queries make a lot more sense when they’re viewed in the context of if(). The if() function works hand-in-hand with style queries, using the same style() function syntax:
/* Container Query Style approach */
@container parent style(--variant: success) {
.element {
background: dodgerblue;
}
}
/* if() function approach */
.element {
background: if(style(--variant: success): dodgerblue; else: gray);
}
Both approaches have their place, but if() is particularly powerful for setting multiple related properties conditionally.
Browser Support and Implementation
Current Support:
- ✅ Chrome 137+ (May 2025)
- ❌ Firefox: Not yet supported
- ❌ Safari: Not yet supported
- ❌ Edge: Not yet supported (follows Chrome)
How to Test:
- Use Chrome 137 or later
- Enable “Experimental Web Platform features” in chrome://flags – optional – sometimes its already active
- Test your CSS if() implementations
Best Practices
1. Use Meaningful Custom Property Names
css/* Good */
.card {
--theme: dark;
--priority: high;
background: if(style(--theme: dark): #333; else: #fff);
}
/* Avoid */
.card {
--x: 1;
--y: 2;
background: if(style(--x: 1): #333; else: #fff);
}
2. Provide Sensible Defaults
Always include an else clause to handle unexpected values:
button {
background: if(
style(--variant: danger): red;
style(--variant: success): green;
else: blue; /* Default fallback */
);
}
3. Combine with Feature Detection
@supports (background: if(style(--test: 1): red; else: blue)) {
/* if() is supported */
.conditional-element {
background: if(style(--theme: dark): #333; else: #fff);
}
}
@supports not (background: if(style(--test: 1): red; else: blue)) {
/* Fallback for browsers without if() support */
.conditional-element {
background: #fff;
}
.conditional-element.dark-theme {
background: #333;
}
}
Performance Considerations
The CSS if() function is evaluated at computed value time, making it highly performant:
- ✅ No JavaScript execution overhead
- ✅ Leverages browser’s CSS engine optimization
- ✅ Works with CSS custom properties inheritance
- ✅ Enables efficient style recalculation
Real-World Use Cases
Design Systems
:root {
--spacing-unit: 8px;
--component-density: normal;
}
.component {
padding: if(
style(--component-density: compact): calc(var(--spacing-unit) * 0.5);
style(--component-density: comfortable): calc(var(--spacing-unit) * 1.5);
else: var(--spacing-unit); /* normal */
);
}
Accessibility Features
.interactive-element {
--reduced-motion: 0; /* Default: animations enabled */
transition-duration: if(
style(--reduced-motion: 1): 0ms;
else: 300ms;
);
transform: scale(if(
style(--reduced-motion: 1): 1;
else: 1.05;
));
}
@media (prefers-reduced-motion: reduce) {
.interactive-element {
--reduced-motion: 1;
}
}
Limitations and Gotchas
- Browser Support: Currently only Chrome 137+
- No Layout Queries: Can’t use with size-based container queries
- Custom Property Dependency: Relies heavily on CSS custom properties
- Debugging: Can be harder to debug than traditional CSS classes
Future Possibilities
The CSS Working Group is considering additional conditional functions:
media()– For media query conditionssupports()– For feature detection conditions- Enhanced boolean algebra support
Summary
If you write any components used and/or styled by others, you know how huge this is! The CSS if() function represents a paradigm shift in how we approach conditional styling. While browser support is currently limited to Chrome 137+, this feature will likely expand quickly across browsers.
Start experimenting with CSS if() today in Chrome, and prepare for a future where conditional logic is a native part of CSS. This feature promises to make our stylesheets more maintainable, our design systems more flexible, and our components more intelligent.
Ready to try it? Download the test file below and start exploring the possibilities of conditional CSS!
CSS if() Function Test Page
Test the revolutionary conditional styling feature in Chrome 137+
1. Theme Toggle Example
This example demonstrates how to use the if() function to create theme switching based on a custom property.
Theme Demo Box
This box changes colors based on the selected theme using the CSS if() function!
2. Button Variants
Create flexible button components with conditional styling for variants and sizes.
3. Status Cards
Display different status cards with conditional colors and icons.
This card changes its appearance based on the selected status using conditional CSS.
4. Responsive Grid Layout
Create responsive grid layouts with conditional column counts and spacing.
5. Typography Scale
Dynamically adjust typography scale using conditional values.
6. Browser Support Test
This section automatically detects if your browser supports the CSS if() function.
CSS if Function: Revolutionary Conditional Styling in Chrome 137+
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