CSS selectors reference
Fern selectors use Tailwind CSS utilities and CSS custom properties. This page is a reference of the stable fern-* selectors for customizing your documentation site.
Layout and structure
Selectors for page layout, backgrounds, and headings.
.fern-background-image
Fixed background image.
.fern-page-heading
Primary page heading (h1).
.fern-layout-page
Page layout container.
.fern-layout-guide
Guide page layout.
.fern-layout-reference
API Reference layout with two-column grid.
.fern-layout-overview
Overview page layout.
.fern-layout-changelog
Changelog page layout.
Header components
Selectors for the site header, tabs, and mobile menu.
#fern-header
Site header container.
.fern-header-tabs
Header navigation tabs (desktop only).
.fern-header-logo-container
Header logo container.
.fern-header-search-bar
Header search input (desktop only).
Sidebar components
Selectors for sidebar navigation and tabs.
.fern-sidebar-header
Top of sidebar.
.fern-sidebar-heading
Sidebar section heading.
.fern-sidebar-heading-content
Sidebar heading text.
.fern-sidebar-link
Sidebar link.
.fern-sidebar-link-title
Sidebar link text.
.fern-sidebar-link-title-inner
Long title marquee animation.
.fern-sidebar-group
Grouped sidebar items.
.fern-sidebar-tabs
Sidebar tab navigation.
Navigation components
Selectors for breadcrumb navigation.
.fern-breadcrumb
Breadcrumb navigation.
.fern-breadcrumb-item
Breadcrumb link or text.
.fern-breadcrumb-arrow
Breadcrumb separator.
Button components
Selectors for buttons.
.fern-button
Button with variants.
Variants:
.minimal- Transparent background with subtle hover.filled- Solid background color.outlined- Border with transparent background.primary- Accent color variant.success- Green color variant.warning- Amber color variant.danger- Red color variant
Size modifiers:
.small- Smaller button (height: 1.75rem on desktop, 1.5rem on mobile).large- Larger button (height: 2.75rem on desktop, 2.5rem on mobile).square- Square button with equal width and height
.fern-button-content
Button content wrapper.
.fern-button-text
Button text.
.fern-button-group
Button group.
.fern-copy-button
Copy button for code blocks.
.fern-expand-button
Expand button for maxLines code blocks.
.fern-page-actions
Page action buttons (edit, feedback, share).
Variants:
.fern-toolbar- Removes the border styling for a toolbar-style appearance
Card components
Selectors for cards.
.fern-card
Card container.
Variants:
.interactive- Adds hover effects.elevated- Elevated appearance with accent border.active- Active state styling
Form components
Selectors for form inputs and controls.
.fern-input
Text input.
.fern-input-group
Input container with focus ring.
.fern-input-icon
Input icon.
.fern-input-right-element
Right-side input element.
.fern-input-clear-button
Input clear button.
.fern-textarea
Multi-line text input.
.fern-textarea-group
Textarea container.
.fern-checkbox-label
Checkbox label.
.fern-checkbox-item
Checkbox input.
.fern-checkbox-indicator
Checked indicator.
.fern-radio-group
Radio button group.
.fern-radio-label
Radio label.
.fern-radio-item
Radio button input.
.fern-radio-indicator
Selected indicator.
.fern-segmented-control
Segmented toggle control.
.fern-numeric-input-group
Numeric input with stepper buttons.
.fern-numeric-input-step
Numeric input stepper button.
Dropdown and selection components
Selectors for dropdowns and the product selector.
.fern-dropdown
Dropdown menu container.
.fern-dropdown-item
Dropdown menu item.
.fern-dropdown-item-indicator
Dropdown selection indicator.
.fern-selection-item
Selection item.
.fern-selection-item-icon
Selection item icon.
.fern-selection-item-title
Selection item title.
.fern-selection-item-end-icon
Selection item end icon.
.fern-product-selector
Product selector. See styles.css for examples.
.fern-product-selector-radio-group
Product selector radio group. See styles.css for examples.
Accordion components
Selectors for accordions.
.fern-accordion
Accordion container.
.fern-accordion-item
Accordion item.
.fern-accordion-trigger
Expand/collapse trigger.
.fern-accordion-trigger-arrow
Expand/collapse arrow.
.fern-accordion-trigger-title
Accordion trigger title.
Scroll area components
Selectors for scrollable areas.
.fern-scroll-area
Scrollable area container.
.fern-scroll-area-viewport
Scroll viewport.
.fern-scroll-area-scrollbar
Scrollbar.
.fern-scroll-area-thumb
Scrollbar thumb.
.fern-scroll-area-corner
Scrollbar corner.
Badge components
Selectors for badges and HTTP method tags.
.fern-docs-badge
Badge for labels, status, and HTTP methods.
MDX content components
Selectors for links, callouts, steps, and tables.
.fern-mdx-link
Link with external icon and hover underline.
.fern-callout
Callout with intent-matched colors.
Intent variants:
[data-intent="info"]- Gray/neutral (default)[data-intent="warning"]- Amber/yellow[data-intent="success"]- Green[data-intent="error"]- Red[data-intent="note"]- Blue[data-intent="launch"]- Accent color[data-intent="tip"]- Green[data-intent="check"]- Green
.fern-indent
Indent with vertical guide line.
.fern-steps
Steps container.
.fern-step
Single step.
.fern-anchor
Anchor for deep linking.
.fern-table-root
Table container.
.fern-table
Table with .sticky support for sticky headers.
Changelog filter components
Selectors for changelog filter UI. Only on changelog pages with tags.
.fern-filter-dropdown-button
Filter dropdown trigger button.
.fern-filter-dropdown-button-text
Filter button text.
.fern-filter-dropdown-button-icon
Filter button chevron.
.fern-filter-dropdown-item
Filter dropdown item.
.fern-filter-badge
Filter badge base class.
.fern-filter-badge-selected
Selected filter badge.
.fern-filter-badge-unselected
Unselected filter badge.
.fern-dropdown-checkmark
Filter dropdown checkmark.
API Reference components
Selectors for API Reference components.
.fern-api-property
API property container.
.fern-api-property-header
API property header.
.fern-api-property-key
API property name.
.fern-api-property-meta
API property metadata (type, required).
.fern-api-property-constraint
API property constraint.
.fern-api-property-optional
“Optional” label on non-required properties. Inherits styles from .fern-api-property-meta.
.fern-api-property-required
“Required” label on required properties.
.fern-api-property-type
API property type label (e.g. “string”, “integer”). Inherits styles from .fern-api-property-meta.
.fern-api-property-default
Default value display for a property.
.fern-api-property-readonly
“Read only” label on read-only properties. Inherits styles from .fern-api-property-meta.
Utility components
Selectors for icons, tooltips, and other elements.
.fern-highlight
Highlighted text.
.fern-mdx-icon
Inline icon (adapts to theme).
.fern-mdx-tooltip-trigger
Tooltip trigger with underline.
.fern-mdx-tooltip-content
Tooltip content.
.fern-file-icon
File type icon.
.fern-collapsible-child
Collapsible child element.
.fern-runnable-endpoint
.fern-rss-feed-button
RSS feed button.
Changelog components
Selectors for changelog pages. The changelog overview renders a feed: a control bar (search and tag filters) above a vertical timeline of entry cards grouped by day. The page layout container is .fern-layout-changelog (documented under Layout and structure).
.fern-changelog-feed
Centered column that holds the changelog header, control bar, and timeline.
.fern-changelog-controls
Control bar with the full-text search and tag filter. Inner elements: .fern-changelog-controls-row and .fern-changelog-search.
.fern-changelog-timeline
Vertical timeline: a left date gutter beside a rail of entry cards. Entries are grouped per day into .fern-changelog-day-group, with the date in .fern-changelog-day and that day’s cards in .fern-changelog-day-entries.
.fern-changelog-card
A single clickable changelog entry card in the timeline. Inner elements: .fern-changelog-card-marker (timeline dot), .fern-changelog-card-body, .fern-changelog-card-title, .fern-changelog-card-link, .fern-changelog-card-excerpt, .fern-changelog-card-preview (rich MDX preview), and .fern-changelog-card-tags.
.fern-changelog-tags
Tag chips as rendered inside a full changelog entry page. In the timeline cards the chips render in .fern-changelog-card-tags. Search matches are highlighted with .fern-changelog-highlight, and .fern-changelog-empty shows when no entries match the active filters.
.fern-changelog-content
Changelog content area.
.fern-changelog-label
Changelog entry label.
Complete selector index
The sections of this page document the most commonly customized selectors in detail. The table below is the complete set of stable fern-* selectors present in the rendered docs, generated from the Fern docs source. Any fern-* selector not in the table doesn’t exist in the rendered site.
| Selector | Type |
|---|---|
.fern-accordion | Class |
.fern-accordion-item | Class |
.fern-accordion-trigger | Class |
.fern-accordion-trigger-arrow | Class |
.fern-accordion-trigger-title | Class |
.fern-air | Class |
.fern-analytics-ga | Class |
.fern-analytics-gtm | Class |
.fern-analytics-segment | Class |
.fern-anchor | Class |
.fern-anchor-icon | Class |
#fern-announcement | ID |
.fern-announcement-dismissed | Class |
.fern-api-property | Class |
.fern-api-property-constraint | Class |
.fern-api-property-default | Class |
.fern-api-property-header | Class |
.fern-api-property-key | Class |
.fern-api-property-meta | Class |
.fern-api-property-optional | Class |
.fern-api-property-readonly | Class |
.fern-api-property-required | Class |
.fern-api-property-type | Class |
#fern-ask-ai-button | ID |
#fern-ask-ai-button-icon | ID |
#fern-ask-ai-panel | ID |
#fern-ask-ai-panel-header | ID |
#fern-ask-ai-panel-header-icon | ID |
#fern-ask-ai-panel-input | ID |
.fern-audio-player | Class |
#fern-auth-button | ID |
.fern-back-to-top | Class |
.fern-background-image | Class |
.fern-bleed | Class |
.fern-breadcrumb | Class |
.fern-breadcrumb-arrow | Class |
.fern-breadcrumb-item | Class |
.fern-button | Class |
.fern-button-content | Class |
.fern-button-group | Class |
.fern-button-text | Class |
.fern-callout | Class |
.fern-card | Class |
.fern-card-group | Class |
.fern-changelog-card | Class |
.fern-changelog-card-body | Class |
.fern-changelog-card-excerpt | Class |
.fern-changelog-card-link | Class |
.fern-changelog-card-marker | Class |
.fern-changelog-card-preview | Class |
.fern-changelog-card-tags | Class |
.fern-changelog-card-title | Class |
.fern-changelog-content | Class |
.fern-changelog-controls | Class |
.fern-changelog-controls-row | Class |
.fern-changelog-day | Class |
.fern-changelog-day-entries | Class |
.fern-changelog-day-group | Class |
.fern-changelog-empty | Class |
.fern-changelog-feed | Class |
.fern-changelog-highlight | Class |
.fern-changelog-highlight-style | Class |
.fern-changelog-label | Class |
.fern-changelog-overview | Class |
.fern-changelog-search | Class |
.fern-changelog-tags | Class |
.fern-changelog-timeline | Class |
.fern-checkbox-indicator | Class |
.fern-checkbox-item | Class |
.fern-checkbox-label | Class |
.fern-code | Class |
.fern-code-actions | Class |
.fern-code-block | Class |
.fern-code-block-actions | Class |
.fern-code-block-content | Class |
.fern-code-block-header | Class |
.fern-code-block-header-inner | Class |
.fern-code-block-title | Class |
.fern-code-block-title-label | Class |
.fern-code-content | Class |
.fern-code-group | Class |
.fern-code-group-actions | Class |
.fern-code-group-content | Class |
.fern-code-group-header | Class |
.fern-code-group-header-inner | Class |
.fern-code-group-tab | Class |
.fern-code-group-tab-label | Class |
.fern-code-group-tabs | Class |
.fern-code-header | Class |
.fern-code-header-inner | Class |
.fern-code-label | Class |
.fern-code-link | Class |
.fern-collapse-trigger | Class |
.fern-collapsible | Class |
.fern-collapsible-card | Class |
.fern-collapsible-card-nested | Class |
.fern-collapsible-card-print-truncated | Class |
.fern-collapsible-child | Class |
.fern-copy-button | Class |
.fern-copy-inline | Class |
.fern-dashboard | Class |
.fern-docs-badge | Class |
.fern-docs-feedback | Class |
.fern-docs-static | Class |
.fern-docs-track-analytics | Class |
.fern-dropdown | Class |
.fern-dropdown-checkmark | Class |
.fern-dropdown-item | Class |
.fern-dropdown-item-indicator | Class |
.fern-endpoint-code-snippets | Class |
.fern-endpoint-request-snippet | Class |
.fern-endpoint-response-snippet | Class |
.fern-endpoint-section-auth | Class |
.fern-endpoint-section-errors | Class |
.fern-endpoint-section-headers | Class |
.fern-endpoint-section-path-parameters | Class |
.fern-endpoint-section-query-parameters | Class |
.fern-endpoint-section-request-body | Class |
.fern-endpoint-section-response-body | Class |
.fern-endpoint-section-response-headers | Class |
.fern-endpoint-selector | Class |
.fern-env-switcher | Class |
.fern-expand-button | Class |
.fern-explorer-auth-form | Class |
.fern-explorer-clear-form-button | Class |
.fern-explorer-endpoint-form | Class |
.fern-explorer-example-selector | Class |
.fern-explorer-form | Class |
.fern-explorer-form-buttons | Class |
.fern-explorer-request-card | Class |
.fern-explorer-request-header | Class |
.fern-explorer-request-title | Class |
.fern-explorer-response-card | Class |
.fern-explorer-response-header | Class |
.fern-explorer-response-title | Class |
.fern-explorer-section-body | Class |
.fern-explorer-section-body-parameters | Class |
.fern-explorer-section-content | Class |
.fern-explorer-section-header | Class |
.fern-explorer-section-headers | Class |
.fern-explorer-section-multipart-form | Class |
.fern-explorer-section-parameters | Class |
.fern-explorer-section-path-parameters | Class |
.fern-explorer-section-query-parameters | Class |
.fern-explorer-send-request-button | Class |
.fern-feedback-button | Class |
.fern-file-icon | Class |
.fern-filter-badge | Class |
.fern-filter-badge-selected | Class |
.fern-filter-badge-unselected | Class |
.fern-filter-dropdown-button | Class |
.fern-filter-dropdown-button-content | Class |
.fern-filter-dropdown-button-icon | Class |
.fern-filter-dropdown-button-text | Class |
.fern-filter-dropdown-item | Class |
#fern-footer | ID |
.fern-footer-nav | Class |
.fern-footer-nav—simple | Class |
.fern-footer-next | Class |
.fern-footer-prev | Class |
.fern-ground | Class |
#fern-header | ID |
.fern-header-content | Class |
.fern-header-height | Class |
.fern-header-logo-container | Class |
.fern-header-mobile-menu-button | Class |
.fern-header-navbar-links | Class |
.fern-header-search-bar | Class |
.fern-header-selectors | Class |
.fern-header-switchers | Class |
.fern-header-switchers-separator | Class |
.fern-header-tabs | Class |
.fern-highlight | Class |
.fern-image-loader | Class |
.fern-indent | Class |
.fern-input | Class |
.fern-input-clear-button | Class |
.fern-input-group | Class |
.fern-input-icon | Class |
.fern-input-right-element | Class |
.fern-kbd | Class |
.fern-language-dropdown-content | Class |
.fern-language-dropdown-item | Class |
.fern-language-dropdown-item-label | Class |
.fern-language-selector | Class |
.fern-language-selector-radio-group | Class |
.fern-layout-changelog | Class |
.fern-layout-changelog-entry | Class |
.fern-layout-content-wrapper | Class |
.fern-layout-footer | Class |
.fern-layout-footer-toolbar | Class |
.fern-layout-guide | Class |
.fern-layout-overview | Class |
.fern-layout-page | Class |
.fern-layout-reference | Class |
.fern-layout-reference-aside | Class |
.fern-layout-reference-content | Class |
.fern-logo-text | Class |
.fern-main | Class |
.fern-mdx-icon | Class |
.fern-mdx-link | Class |
.fern-mdx-tooltip-content | Class |
.fern-mdx-tooltip-trigger | Class |
.fern-mermaid | Class |
.fern-navigation-storage | Class |
.fern-not-found-shell | Class |
.fern-numeric-input-group | Class |
.fern-numeric-input-step | Class |
.fern-page-actions | Class |
.fern-page-heading | Class |
.fern-page-roles | Class |
.fern-page-subtitle | Class |
.fern-pdf-cover-date | Class |
.fern-pdf-cover-footer | Class |
.fern-pdf-cover-footer-brand | Class |
.fern-pdf-cover-root | Class |
.fern-pdf-cover-subtitle | Class |
.fern-pdf-cover-title | Class |
.fern-playground-field | Class |
.fern-playground-field-actions | Class |
.fern-playground-field-block | Class |
.fern-playground-field-control | Class |
.fern-playground-field-count | Class |
.fern-playground-field-header | Class |
.fern-playground-field-help-icon | Class |
.fern-playground-field-inline | Class |
.fern-playground-field-item | Class |
.fern-playground-field-key | Class |
.fern-playground-field-label | Class |
.fern-playground-field-list | Class |
.fern-playground-field-remove | Class |
.fern-playground-field-type | Class |
.fern-playground-floating-button | Class |
.fern-playground-object-properties | Class |
.fern-product-item | Class |
.fern-product-item-link | Class |
.fern-product-selector | Class |
.fern-product-selector-radio-group | Class |
.fern-product-tabs | Class |
.fern-product-tabs-row | Class |
.fern-programming-language | Class |
.fern-prompt | Class |
.fern-prompt-code | Class |
.fern-prompt-code-wrapper | Class |
.fern-prompt-icon | Class |
.fern-prompt-icon-wrapper | Class |
.fern-prose | Class |
.fern-radio-group | Class |
.fern-radio-indicator | Class |
.fern-radio-item | Class |
.fern-radio-label | Class |
.fern-rss-feed-button | Class |
.fern-runnable-actions | Class |
.fern-runnable-auth | Class |
.fern-runnable-auth-content | Class |
.fern-runnable-auth-fields | Class |
.fern-runnable-auth-title | Class |
.fern-runnable-auth-toggle | Class |
.fern-runnable-card | Class |
.fern-runnable-clear-button | Class |
.fern-runnable-endpoint | Class |
.fern-runnable-endpoint-values | Class |
.fern-runnable-form | Class |
.fern-runnable-form-inner | Class |
.fern-runnable-header | Class |
.fern-runnable-header-actions | Class |
.fern-runnable-header-inner | Class |
.fern-runnable-response | Class |
.fern-runnable-response-header | Class |
.fern-runnable-response-label | Class |
.fern-runnable-response-meta | Class |
.fern-runnable-response-size | Class |
.fern-runnable-response-status | Class |
.fern-runnable-response-time | Class |
.fern-runnable-section-content | Class |
.fern-runnable-section-title | Class |
.fern-runnable-send-button | Class |
.fern-scroll-area | Class |
.fern-scroll-area-corner | Class |
.fern-scroll-area-scrollbar | Class |
.fern-scroll-area-scrollbar-fade-in | Class |
.fern-scroll-area-scrollbar-fade-out | Class |
.fern-scroll-area-thumb | Class |
.fern-scroll-area-viewport | Class |
.fern-scroll-walkthrough | Class |
.fern-scroll-walkthrough-aside | Class |
.fern-scroll-walkthrough-aside-sticky | Class |
.fern-scroll-walkthrough-code | Class |
.fern-scroll-walkthrough-main | Class |
.fern-scroll-walkthrough-panel | Class |
.fern-scroll-walkthrough-panel-header | Class |
.fern-scroll-walkthrough-panel-header-inner | Class |
.fern-scroll-walkthrough-spacer | Class |
.fern-scroll-walkthrough-step-body | Class |
.fern-scroll-walkthrough-step-description | Class |
.fern-scroll-walkthrough-step-detail | Class |
.fern-scroll-walkthrough-step-head | Class |
.fern-scroll-walkthrough-step-item | Class |
.fern-scroll-walkthrough-step-marker | Class |
.fern-scroll-walkthrough-step-title | Class |
.fern-scroll-walkthrough-steps | Class |
.fern-scroll-walkthrough-substep | Class |
.fern-scroll-walkthrough-substep-body | Class |
.fern-scroll-walkthrough-substep-code | Class |
.fern-scroll-walkthrough-substep-content | Class |
.fern-scroll-walkthrough-substep-marker | Class |
.fern-scroll-walkthrough-substep-title | Class |
.fern-scroll-walkthrough-substeps | Class |
.fern-scroll-walkthrough-tab | Class |
.fern-scroll-walkthrough-tabs | Class |
#fern-search-button | ID |
.fern-search-desktop-command | Class |
#fern-search-dialog | ID |
#fern-search-dialog-overlay | ID |
.fern-search-hit-breadcrumb | Class |
.fern-search-hit-endpoint-path | Class |
.fern-search-hit-highlighted | Class |
.fern-search-hit-non-highlighted | Class |
.fern-search-hit-snippet | Class |
.fern-search-hit-title | Class |
#fern-search-mobile-command | ID |
.fern-segmented-control | Class |
.fern-selection-item | Class |
.fern-selection-item-end-icon | Class |
.fern-selection-item-icon | Class |
.fern-selection-item-subtitle | Class |
.fern-selection-item-title | Class |
#fern-sidebar | ID |
.fern-sidebar-desktop | Class |
.fern-sidebar-group | Class |
.fern-sidebar-group-level-1 | Class |
.fern-sidebar-group-root | Class |
.fern-sidebar-header | Class |
.fern-sidebar-heading | Class |
.fern-sidebar-heading-content | Class |
.fern-sidebar-level-0 | Class |
.fern-sidebar-link | Class |
.fern-sidebar-link-inline-badge | Class |
.fern-sidebar-link-title | Class |
.fern-sidebar-link-title-inner | Class |
.fern-sidebar-marquee | Class |
#fern-sidebar-overlay | ID |
#fern-sidebar-scroll-area | ID |
.fern-sidebar-scroll-position | Class |
#fern-sidebar-spacer | ID |
.fern-sidebar-tabs | Class |
.fern-step | Class |
.fern-steps | Class |
.fern-stream | Class |
.fern-table | Class |
.fern-table-collapse | Class |
.fern-table-pagination | Class |
.fern-table-pagination-controls | Class |
.fern-table-pagination-label | Class |
.fern-table-root | Class |
.fern-table-search | Class |
.fern-table-search-clear | Class |
.fern-table-search-icon | Class |
.fern-table-search-input | Class |
.fern-table-show-all | Class |
.fern-textarea | Class |
.fern-textarea-group | Class |
#fern-theme-color | ID |
#fern-theme-color-preferred-dark | ID |
#fern-theme-color-preferred-light | ID |
#fern-toc | ID |
.fern-token | Class |
.fern-toolbar | Class |
.fern-user | Class |
.fern-variant-selector | Class |
.fern-variant-selector-dropdown | Class |
.fern-variant-selector-radio-group | Class |
.fern-version-selector | Class |
.fern-version-selector-radio-group | Class |
.fern-walkthrough | Class |
.fern-walkthrough-aside | Class |
.fern-walkthrough-aside-sticky | Class |
.fern-walkthrough-close | Class |
.fern-walkthrough-control | Class |
.fern-walkthrough-controls | Class |
.fern-walkthrough-frame | Class |
.fern-walkthrough-progress | Class |
.fern-walkthrough-step | Class |
.fern-walkthrough-step-body | Class |
.fern-walkthrough-step-description | Class |
.fern-walkthrough-step-item | Class |
.fern-walkthrough-step-number | Class |
.fern-walkthrough-step-title | Class |
.fern-walkthrough-steps | Class |
.fern-walkthrough-toolbar | Class |
.fern-web-socket-badge | Class |
.fern-web-socket-chevron | Class |
.fern-web-socket-client | Class |
.fern-web-socket-content | Class |
.fern-web-socket-copy | Class |
.fern-web-socket-end-sample | Class |
.fern-web-socket-server | Class |
.fern-web-socket-trigger | Class |
.fern-web-socket-trigger-data | Class |
.fern-web-socket-type | Class |
.fern-x-overflow | Class |