Modifiers

Pseudo-Elements Modifiers

Create pseudo-element modifiers for targeting element sub-parts like before, after, placeholder, and selection with full type safety.

Part of the Modifiers Preset:usePseudoElementModifiers is included in the Modifiers Preset (useModifiersPreset) and you can configure it through the preset's pseudoElements option. For most projects, applying it via the preset is the recommended approach.

Overview

Pseudo-element modifiers let you apply utility styles to specific sub-parts of an element. They wrap utility declarations in CSS pseudo-element selectors like ::before, ::after, and ::placeholder, generating variant utility classes that target these element fragments.

Why Use Pseudo-Element Modifiers?

Pseudo-element modifiers help you:

Style generated content: Control the appearance of ::before and ::after pseudo-elements
Customize form placeholders: Style placeholder text without custom CSS
Enhance text selection: Change the appearance of selected text
Style list markers: Customize bullet points and list numbers
Target file inputs: Style the file upload button in file input elements

`useBeforeModifier`

The useBeforeModifier() function creates a modifier that applies styles to the ::before pseudo-element. It automatically injects content: '' to ensure the pseudo-element is rendered.

styleframe.config.ts

import { styleframe } from "styleframe";
import { useBackgroundColorUtility, useWidthUtility, useHeightUtility } from "@styleframe/theme";
import { useBeforeModifier } from "@styleframe/theme";

const s = styleframe();

const before = useBeforeModifier(s);

useBackgroundColorUtility(s, {
    primary: '#006cff',
}, [before]);

useWidthUtility(s, {
    full: '100%',
}, [before]);

useHeightUtility(s, {
    px: '1px',
}, [before]);

export default s;

styleframe/index.css

._background-color\:primary { background-color: #006cff; }

._before\:background-color\:primary {
    &::before { content: ''; background-color: #006cff; }
}

._before\:width\:full {
    &::before { content: ''; width: 100%; }
}

._before\:height\:px {
    &::before { content: ''; height: 1px; }
}

<!-- Add a decorative line before an element -->
<h2 class="_before:background-color:primary _before:width:full _before:height:px">
    Section Title
</h2>

CSS Selector

Modifier Name	CSS Selector	Auto-injected
`before`	`&::before`	`content: ''`

Pro tip: The before and after modifiers automatically inject content: '' into the declarations. This ensures the pseudo-element is rendered without requiring a separate content utility.

`useAfterModifier`

The useAfterModifier() function creates a modifier that applies styles to the ::after pseudo-element. It automatically injects content: ''.

styleframe.config.ts

import { styleframe } from "styleframe";
import { useBackgroundColorUtility } from "@styleframe/theme";
import { useAfterModifier } from "@styleframe/theme";

const s = styleframe();

const after = useAfterModifier(s);

useBackgroundColorUtility(s, {
    overlay: 'rgba(0, 0, 0, 0.5)',
}, [after]);

export default s;

styleframe/index.css

._background-color\:overlay { background-color: rgba(0, 0, 0, 0.5); }

._after\:background-color\:overlay {
    &::after { content: ''; background-color: rgba(0, 0, 0, 0.5); }
}

<!-- Add an overlay after an element -->
<div class="_after:background-color:overlay">
    Content with overlay
</div>

CSS Selector

Modifier Name	CSS Selector	Auto-injected
`after`	`&::after`	`content: ''`

`usePlaceholderModifier`

The usePlaceholderModifier() function creates a modifier that applies styles to the ::placeholder pseudo-element of form inputs.

styleframe.config.ts

import { styleframe } from "styleframe";
import { useTextColorUtility, useOpacityUtility } from "@styleframe/theme";
import { usePlaceholderModifier } from "@styleframe/theme";

const s = styleframe();

const placeholder = usePlaceholderModifier(s);

useTextColorUtility(s, {
    muted: '#6c757d',
}, [placeholder]);

useOpacityUtility(s, {
    75: '0.75',
}, [placeholder]);

export default s;

styleframe/index.css

._text-color\:muted { color: #6c757d; }

._placeholder\:text-color\:muted {
    &::placeholder { color: #6c757d; }
}

._placeholder\:opacity\:75 {
    &::placeholder { opacity: 0.75; }
}

<input
    class="_placeholder:text-color:muted _placeholder:opacity:75"
    placeholder="Enter your name..."
>

CSS Selector

Modifier Name	CSS Selector
`placeholder`	`&::placeholder`

`useSelectionModifier`

The useSelectionModifier() function creates a modifier that applies styles to the text selection highlight.

styleframe.config.ts

import { styleframe } from "styleframe";
import { useBackgroundColorUtility, useTextColorUtility } from "@styleframe/theme";
import { useSelectionModifier } from "@styleframe/theme";

const s = styleframe();

const selection = useSelectionModifier(s);

useBackgroundColorUtility(s, {
    primary: '#006cff',
}, [selection]);

useTextColorUtility(s, {
    white: '#ffffff',
}, [selection]);

export default s;

styleframe/index.css

._selection\:background-color\:primary {
    &::selection { background-color: #006cff; }
}

._selection\:text-color\:white {
    &::selection { color: #ffffff; }
}

<!-- Custom text selection colors -->
<p class="_selection:background-color:primary _selection:text-color:white">
    Select this text to see custom highlight colors.
</p>

CSS Selector

Modifier Name	CSS Selector
`selection`	`&::selection`

`useFirstLetterModifier`

The useFirstLetterModifier() function creates a modifier that applies styles to the first letter of a text block.

CSS Selector

Modifier Name	CSS Selector
`first-letter`	`&::first-letter`

`useFirstLineModifier`

The useFirstLineModifier() function creates a modifier that applies styles to the first line of a text block.

CSS Selector

Modifier Name	CSS Selector
`first-line`	`&::first-line`

`useMarkerModifier`

The useMarkerModifier() function creates a modifier that applies styles to list item markers (bullets, numbers).

styleframe.config.ts

import { styleframe } from "styleframe";
import { useTextColorUtility } from "@styleframe/theme";
import { useMarkerModifier } from "@styleframe/theme";

const s = styleframe();

const marker = useMarkerModifier(s);

useTextColorUtility(s, {
    primary: '#006cff',
}, [marker]);

export default s;

styleframe/index.css

._marker\:text-color\:primary {
    &::marker { color: #006cff; }
}

<ul>
    <li class="_marker:text-color:primary">Colored bullet item</li>
    <li class="_marker:text-color:primary">Another item</li>
</ul>

CSS Selector

Modifier Name	CSS Selector
`marker`	`&::marker`

`useBackdropModifier`

The useBackdropModifier() function creates a modifier that applies styles to the ::backdrop pseudo-element, used with <dialog> elements and fullscreen API.

CSS Selector

Modifier Name	CSS Selector
`backdrop`	`&::backdrop`

`useFileModifier`

The useFileModifier() function creates a modifier that applies styles to the file upload button in <input type="file"> elements.

CSS Selector

Modifier Name	CSS Selector
`file`	`&::file-selector-button`

`usePseudoElementModifiers`

The usePseudoElementModifiers() function registers all pseudo-element modifiers at once and returns them as a destructurable object.

styleframe.config.ts

import { styleframe } from "styleframe";
import { useTextColorUtility, useBackgroundColorUtility } from "@styleframe/theme";
import { usePseudoElementModifiers } from "@styleframe/theme";

const s = styleframe();

const { before, after, placeholder, selection } = usePseudoElementModifiers(s);

useTextColorUtility(s, {
    muted: '#6c757d',
    white: '#ffffff',
}, [placeholder, selection]);

useBackgroundColorUtility(s, {
    primary: '#006cff',
}, [before, after, selection]);

export default s;

<input class="_placeholder:text-color:muted" placeholder="Styled placeholder">

<p class="_selection:background-color:primary _selection:text-color:white">
    Custom selection highlight
</p>

Returned Modifiers

Key	Modifier Name	CSS Selector	Notes
`before`	`before`	`&::before`	Auto-injects `content: ''`
`after`	`after`	`&::after`	Auto-injects `content: ''`
`placeholder`	`placeholder`	`&::placeholder`
`selection`	`selection`	`&::selection`
`firstLetter`	`first-letter`	`&::first-letter`
`firstLine`	`first-line`	`&::first-line`
`marker`	`marker`	`&::marker`
`backdrop`	`backdrop`	`&::backdrop`
`file`	`file`	`&::file-selector-button`

Examples

Drop Cap Typography

styleframe.config.ts

import { styleframe } from "styleframe";
import { useFontSizeUtility, useFontWeightUtility, useTextColorUtility } from "@styleframe/theme";
import { useFirstLetterModifier } from "@styleframe/theme";

const s = styleframe();

const firstLetter = useFirstLetterModifier(s);

useFontSizeUtility(s, {
    '3xl': '3rem',
}, [firstLetter]);

useFontWeightUtility(s, {
    bold: '700',
}, [firstLetter]);

useTextColorUtility(s, {
    primary: '#006cff',
}, [firstLetter]);

export default s;

<p class="_first-letter:font-size:3xl _first-letter:font-weight:bold _first-letter:text-color:primary">
    Once upon a time, there was a beautiful drop cap that started a paragraph.
</p>

Styled File Input

styleframe.config.ts

import { styleframe } from "styleframe";
import { useBackgroundColorUtility, useTextColorUtility } from "@styleframe/theme";
import { useFileModifier, useHoverModifier } from "@styleframe/theme";

const s = styleframe();

const file = useFileModifier(s);
const hover = useHoverModifier(s);

useBackgroundColorUtility(s, {
    primary: '#006cff',
}, [file]);

useTextColorUtility(s, {
    white: '#ffffff',
}, [file]);

export default s;

<input
    type="file"
    class="_file:background-color:primary _file:text-color:white"
>

Best Practices

Use before/after for decorative content: Pseudo-elements are ideal for decorative elements that don't need to be in the DOM
Style placeholders subtly: Use muted colors for placeholder text to distinguish it from actual input values
Customize selection colors to match your brand: Use the selection modifier for on-brand text highlighting
Remember content injection: The before and after modifiers auto-inject content: ''; override this if you need specific content
Test marker styles: Not all CSS properties work with ::marker; it supports a limited set including color, font-size, and content

FAQ

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Other State

Create other state modifiers for targeting open and inert elements with full type safety.

Pseudo-State

Create pseudo-state modifiers for interactive states like hover, focus, active, and more with full type safety.