FlexLayout

FlexLayout is a layout manager for React that arranges components in multiple tabsets. Tabs can be resized, moved, and organized into complex layouts.

Run the Demo

Examples

Example in CodeSandbox

API Doc

FlexLayout's only dependency is React.

Features:

• Tabs (scrolling or wrapped) — see Tab Wrapping / Many Tabs
• Pinnable tabs — see Pinned Tabs
• Tab groups (Chrome-style colored group pills) — see Tab Groups / example
• Border tabsets: splitting the layout or overlaying it, with autohide when empty option — see Borders
• Tabset dragging (move all tabs in a tabset in one operation)
• Docking to tabsets or edges of the frame
• Maximizing tabsets (double-click tabset header or use icon)
• Tab overflow (menu for hidden tabs, mouse wheel scrolling) — see Many Tabs
• Popout tabs into floating panels or new browser windows — see Popout
• Submodels (layouts inside layouts) — see Sublayout
• Theming (light, dark, underline, etc., and combined) — see Theme
• Accessibility (ARIA roles, keyboard operation with a configurable keymap, visible focus) — see Accessibility
• Mobile support (iPad, Android)
• Multiple ways to add tabs (drag, active tabset, by ID) — see External Drag / Sticky Button
• Comprehensive tab and tabset attributes (enableTabStrip, enableDock, enableDrop, etc.) — see Min Sizes
• Customizable tab and tabset rendering — see Tab Rendering / Tabset Rendering
• Tabset placeholder for empty tabsets — see Placeholder
• Support for internationalization — see i18n
• Preservation of component state when tabs are moved
• TypeScript type declarations

FlexLayout is available on npm. Install it using:

npm install flexlayout-react

The package is ESM-only and must be consumed via import (it cannot be loaded with require()). Import FlexLayout and its model in your modules:

import { Layout, Model, Actions, DockLocation } from 'flexlayout-react';

Include a theme. Choose from alpha_light, alpha_dark, alpha_rounded, light, dark, underline, gray, rounded, or combined (see the demo for examples):

import 'flexlayout-react/style/alpha_light.css';

Learn how to change the theme dynamically in code

The <Layout> component renders the tabsets and splitters. It takes the following props:

Additional optional props

The model is a tree of Node objects that define the structure of the layout.

The factory is a function that takes a Node object and returns a React component to be hosted within a tab.

Models can be created using the Model.fromJson(jsonObject) static method and saved using the model.toJson() method.

const json = {
    global: {},
    borders: [],
    layout: {
        type: "row",
        weight: 100,
        children: [
            {
                type: "tabset",
                weight: 50,
                children: [
                    {
                        type: "tab",
                        name: "One",
                        component: "placeholder",
                    }
                ]
            },
            {
                type: "tabset",
                weight: 50,
                children: [
                    {
                        type: "tab",
                        name: "Two",
                        component: "placeholder",
                    }
                ]
            }
        ]
    }
};

const model = Model.fromJson(json);

function App() {

  const factory = (node) => {
    const component = node.getComponent();

    if (component === "placeholder") {
      return <div>{node.getName()}</div>;
    }
  }

  return (
    <Layout
      model={model}
      factory={factory} />
  );
}

The above code renders two tabsets horizontally, each containing a single tab that hosts a div component (returned from the factory). Tabs can be moved and resized by dragging and dropping. Additional tabs can be added to the layout by sending actions to the model.

Try it now using CodeSandbox — see Basic — examples/basic/Basic.tsx.

Note: The <Layout> component must be hosted in a container element (with CSS position: absolute or relative). The layout will fill the containing element.

A simple TypeScript starter project can be found here:

https://github.com/nealus/flexlayout-vite-example

The model JSON contains four top-level elements:

• global - (optional) Global options.
• layout - The main row/tabset/tabs layout hierarchy.
• borders - (optional) Up to four borders ("top", "bottom", "left", "right").
• subLayouts - (optional) Where sub layouts for popout windows, floating panels and tabs are defined.

The layout element is built using three types of nodes:

• row - Rows contain a list of tabsets and child rows. The top-level row renders horizontally by default (unless the global attribute rootOrientationVertical is set). Child rows render in the opposite orientation to their parent row.
• tabset - Tabsets contain a list of tabs and the index of the selected tab.
• tab - Tabs specify the component to host (loaded via the factory) and the tab's display text.

The layout structure is defined with rows within rows that contain tabsets that themselves contain tabs.

Within the demo app, you can view the layout structure by checking the 'Structure' box. Rows are shown in blue, and tabsets in orange.

The optional borders element is made up of border nodes:

• border - Borders contain a list of tabs and the index of the selected tab. They can only be used within the borders top-level element.

The JSON model tree structure is defined as TypeScript interfaces; see JSON Model.

Each node type has a defined set of required and optional attributes.

Weights on rows and tabsets specify their relative size within the parent row. The absolute values do not matter, only their proportions (e.g., two tabsets with weights 30 and 70 would render the same as if they had weights 3 and 7).

NOTE: The easiest way to create your initial layout JSON is to use the demo app. Modify an existing layout by dragging, dropping, and adding nodes, then press the 'print' button to print the JSON to the browser's developer console. Use the Model Explorer panel to view and modify the attributes of the layout and its nodes, and use the render dropdown in the demo to blank out the panels (other than the Model Explorer) so you can focus on the layout.

By changing global or node attributes, you can modify the layout's appearance and functionality. For example, setting tabSetEnableTabStrip: false in the global options would change the layout into a multi-splitter (without tabs or drag-and-drop):

 global: {tabSetEnableTabStrip:false},

Node attributes inherit their default value from the corresponding global attribute, so you can set a value for all nodes of a type in one place and override it per-node. The global attribute is the node attribute prefixed with the node type: tab for tab attributes (e.g. tabEnableClose), tabSet for tabset attributes (e.g. tabSetEnableDrag), and border for border attributes (e.g. borderSize).

For example, to make all tabs non-closeable but allow the tab with id "persistent" to be closed anyway:

{
    "global": { "tabEnableClose": false },
    "layout": {
        "type": "row",
        "children": [
            {
                "type": "tabset",
                "children": [
                    { "type": "tab", "name": "One", "component": "placeholder" },
                    { "type": "tab", "name": "Two", "component": "placeholder" },
                    { "type": "tab", "id": "persistent", "name": "Persistent", "component": "placeholder", "enableClose": true }
                ]
            }
        ]
    }
}

The "Persistent" tab's enableClose: true overrides the inherited global default of false; the other tabs keep the global value.

The combined.css theme includes all other themes and supports dynamic theme switching.

When using combined.css, add a className (in the form flexlayout__theme_[theme-name]) to the div containing the <Layout> to select the desired theme.

For example:

    <div ref={containerRef} className="flexlayout__theme_alpha_light">
        <Layout model={model} factory={factory} />
    </div>

Change the theme in code by changing the className on the containing div.

For example:

    containerRef.current!.className = "flexlayout__theme_alpha_dark"

See Theme — examples/theme/Theme.tsx.

All themeable values (--fl-color-*, --fl-font-*, --fl-splitter-size, --fl-tab-button-radius, etc.) are CSS custom properties defined in style/_themes.scss. Each one is defined as var(--flexlayout-<name>, <theme default>) — so the theme default applies unless the matching global --flexlayout-<name> variable is defined, in which case that value is used everywhere (float windows, sublayouts, and popout windows included).

To restyle the whole layout without rebuilding the scss, set the global variable on a common ancestor (e.g. :root or the div wrapping the <Layout>):

:root {
    --flexlayout-color-1: #90a4ae;                 /* base color, feeds derived colors */
    --flexlayout-color-tabset-background: #ffffff;  /* or override a specific value */
    --flexlayout-splitter-size: 10px;
}

Override a --flexlayout-<name> variable and every theme uses it; leave it unset and each theme keeps its own default (so theme switching is unaffected). The single-theme stylesheets (light.css, dark.css, etc.) work the same way — a global override reaches every layout on the page, including float windows.

You can use the <Layout> prop onRenderTab to customize tab rendering:

Update the renderValues parameter as needed:

renderValues.leading: The area shown in red.

renderValues.content: The area shown in green.

renderValues.buttons: The area shown in yellow.

For example:

onRenderTab = (node: TabNode, renderValues: ITabRenderValues) => {
    // renderValues.leading = <img style={{width:"1em", height:"1em"}}src="/api/v1/web-embed/proxy?proxyUrl=https%3A%2F%2Fgithub.com%2Fcaplin%2Fimages%2Ffolder.svg&mode=full"/>;
    // renderValues.content += " *";
    renderValues.buttons.push(<img key="menu" style={{width:"1em", height:"1em"}} src="images/menu.svg"/>);
}

See Tab Rendering — examples/tab-rendering/TabRendering.tsx.

You can use the <Layout> prop onRenderTabSet to customize tabset rendering:

Update the renderValues parameter as needed:

renderValues.leading: The area shown in blue.

renderValues.stickyButtons: The area shown in red.

renderValues.buttons: The area shown in green.

For example:

onRenderTabSet = (node: (TabSetNode | BorderNode), renderValues: ITabSetRenderValues) => {
    renderValues.stickyButtons.push(
        <button
            key="Add"
            title="Add"
            className="flexlayout__tab_toolbar_button"
            onClick={() => {
                model.doAction(Actions.addTab({
                    component: "placeholder",
                    name: "Added " + nextAddIndex.current++
                }, node.getId(), DockLocation.CENTER, -1, true));
            }}
        ><AddIcon/></button>);

    renderValues.buttons.push(<img key="menu" style={{width:"1em", height:"1em"}} src="images/menu.svg"/>);
}

See Tabset Rendering — examples/tabset-rendering/TabSetRendering.tsx and Sticky Button — examples/sticky-button/StickyButton.tsx.

The built-in icons (close, pin, maximize/restore, popout, float, overflow, etc.) can be replaced via the icons layout prop. Each entry of the IIcons object is either a React node or a function receiving the relevant node and returning one:

<Layout
    model={model}
    factory={factory}
    icons={{
        close: <MyCloseIcon />,
        // functions receive the node, so the icon can depend on its state;
        // 'more' also receives the hidden tabs, e.g. to show a count
        more: (node, hiddenTabs) => <div>{hiddenTabs.length}</div>,
    }}
/>

The default icons are also exported (CloseIcon, PinIcon, MaximizeIcon, ...) for reuse in your own toolbars and menus. Icons are decorative to assistive technology (the buttons carry their own accessible names), so custom icons do not need alt text.

All text — both model data (tab names, group names, tabset names) and built-in UI labels (button tooltips, context menu items) — is routed through the i18nTranslator layout prop. The function receives a string key and must return the translated string. Built-in UI labels use keys from the I18nLabel enum (e.g. "flexlayout.ui.close.tab", "flexlayout.ui.menu.rename"). If no translator is registered, the default English text is used automatically:

const translations: Record<string, Record<string, string>> = {
    en: {
        // model text (any keys you like)
        "tab.welcome": "Welcome",
        "tab.settings": "Settings",
        // built-in UI labels (I18nLabel enum values)
        "flexlayout.ui.close.tab": "Close",
        "flexlayout.ui.menu.pin": "Pin",
        "flexlayout.ui.menu.rename": "Rename",
        "flexlayout.ui.menu.close.all": "Close All",
    },
    de: {
        "tab.welcome": "Willkommen",
        "tab.settings": "Einstellungen",
        "flexlayout.ui.close.tab": "Schließen",
        "flexlayout.ui.menu.pin": "Anheften",
        "flexlayout.ui.menu.rename": "Umbenennen",
        "flexlayout.ui.menu.close.all": "Alle schließen",
    },
};

const getTranslator = (lang: string) => (key: string) => translations[lang][key] ?? key;

<Layout
    model={model}
    factory={factory}
    i18nTranslator={getTranslator("de")}
/>

Model strings are passed through the translator as-is (use whatever key scheme you like in your JSON). Built-in UI keys follow the pattern flexlayout.ui.<category>.<name> — return the key unchanged to keep the default English text. See examples/i18n/ for a complete working example with language switching and translated context menus.

Use the ContextMenuBuilder to build a custom menu, choosing which options to show, interleaving your own entries and placing dividers, then show it with showPopupMenu from a right-click handler:

import { showPopupMenu, ContextMenuBuilder } from "flexlayout-react";

const onContextMenu = (node: TabNode | TabSetNode | BorderNode, event: React.MouseEvent) => {
    event.preventDefault();
    event.stopPropagation();
    
    const container = node.getLayoutRef()!;
    if (!container) return;

    const items = new ContextMenuBuilder(node)
        .add("rename")
        .addCustom({ key: "my-command", label: "My Command", onSelect: () => doThing() })
        .add("pin")
        .addDivider()
        .add("close")
        .build();
    showPopupMenu({
        anchor: { x: event.clientX, y: event.clientY },
        items,
        onClose: () => {},
        container
    });
};

<Layout model={model} factory={factory} onContextMenu={onContextMenu} />

The items returned by build() (and the getNodeContextMenuItems helper) are plain data, so they don't have to be shown via showPopupMenu — you can render them in your own styled menu component. Each item's label is the menu text already resolved through the layout's i18nTranslator, and its onSelect fires the corresponding action against the node's model.

See Context Menu — examples/context-menu/ContextMenu.tsx.

Once the model JSON has been loaded, all changes are applied through actions. In the Demo app, you can view these actions in the 'Action Log':

Apply actions using the model.doAction() method. This method takes a single argument created by one of the action generators (accessible via the Actions import):

Actions Documentation

model.doAction(Actions.addTab(
    {type:"tab", component:"grid", name:"a grid", id:"5"},
    "1", DockLocation.CENTER, 0));

This example adds a new grid component to the center of the tabset with ID "1" at the first position (0). Use -1 to add to the end of the tabs.

Note: You can retrieve the ID of a node (e.g., the node returned by the addTab action) using node.getId(). If an ID wasn't assigned when the node was created, one will be generated for you in the form #<uuid> (e.g., #0c459064-8dee-444e-8636-eb9ab910fb27).

Note: You can intercept actions resulting from GUI changes before they are applied by implementing the onAction callback property of the Layout.

The useUndo React hook encapsulates undo/redo for a model. It owns the model state, records an undo snapshot before each mutation (so an entire drag gesture collapses into a single step), and replaces the model on undo/redo via Model.fromJson, keeping mounted tab content intact:

function App() {
    const { model, setModel, undo, redo, canUndo, canRedo, undoCount, redoCount } = useUndo(Model.fromJson(initialJson));

    return (
        <>
            <Layout model={model} factory={factory} />
            <button onClick={undo} disabled={!canUndo} title={"undo (" + undoCount + ")"}>Undo</button>
            <button onClick={redo} disabled={!canRedo} title={"redo (" + redoCount + ")"}>Redo</button>
        </>
    );
}

Notes:

• The model can be passed lazily (a function evaluated once), or omitted and loaded later: const { model, setModel, ... } = useUndo(); then setModel(Model.fromJson(json)).
• setModel(model) replaces the model and clears the history; pass false as a second argument to keep the history (e.g. for an in-place round-trip of the same model). Use reset() to clear the history without replacing the model.
• Options: maxBufferSize (default 100) and ignoreActionTypes (default [Actions.SET_ACTIVE_TABSET]) - actions whose types are listed do not create undo steps.

See Undo / Redo — examples/undo-redo/UndoRedo.tsx.

Tabs can be grouped into Chrome-style groups, rendered as a colored pill in the tab strip. A group is a "tabgroup" node that is a direct child of a tabset or border and holds the group's tabs as children.

A group is shown in one of two visual styles, chosen by the global attribute tabGroupType ("splitpill" by default, or "underline"):

{
    "global": { "tabGroupType": "splitpill" }
}

"splitpill" encloses the group's tabs in a pill with left/right caps:

"underline" shows a fully-rounded pill followed by tabs that each carry the group color as an underline:

{
    "type": "tabgroup",
    "id": "g1",
    "name": "Design",
    "color": "#7895c4",
    "opened": true,
    "children": [
        { "type": "tab", "name": "Colors", "component": "label" },
        { "type": "tab", "name": "Typography", "component": "label" }
    ]
}

The group pill shows the group's name and is filled with the group's color. Clicking the pill collapses/expands the group; when collapsed ("opened": false) only the pill is shown, with a count of its hidden tabs.

Groups support drag-and-drop: drag a tab onto a pill to add it to the group, drag a tab out to remove it, and drag the pill itself to reorder or move the whole group. Right-clicking a pill opens a menu to rename the group, change its color, collapse/expand, or ungroup it.

Use these actions to manage groups programmatically:

model.doAction(Actions.addTabToNewGroup("tab5", "Design", "#7895c4")); // move a tab into a new group
model.doAction(Actions.ungroup("g1"));                                 // return a group's tabs to the tabset
model.doAction(Actions.removeTabFromGroup("tab2"));                    // move a tab out of its group

For an example see Tab Groups — examples/tab-groups/TabGroups.tsx (also the Tab Groups layout in the demo app).

When a tabset has no tabs and it's the last tabset or has tabSetEnableDeleteWhenEmpty: false then you can show custom content by providing a onTabSetPlaceHolder callback on the <Layout>:

const json: IJsonModel = {
  global: { tabSetEnableDeleteWhenEmpty: false },
  layout: { type: "row", children: [{ type: "tabset", id: "ts0", children: [] }] }
};

function Placeholder() {
  const layoutRef = useRef<ILayoutApi>(null);
  let nextId = 0;
  const onTabSetPlaceHolder = (node: TabSetNode) => (
    <div style={{ display: "flex", flexGrow: 1, alignItems: "center", justifyContent: "center", flexDirection: "column", gap: 8 }}>
      <div>Drop a tab here</div>
      <button onClick={() => layoutRef.current?.addTabToTabSet(node.getId(), { name: "Tab " + nextId++, component: "panel" })}>
        Add a tab
      </button>
    </div>
  );
  return <Layout ref={layoutRef} model={model} factory={factory} onTabSetPlaceHolder={onTabSetPlaceHolder} />;
}

The callback receives the empty TabSetNode and should return a flex-filled element (flexGrow: 1). See Placeholder — examples/placeholder/Placeholder.tsx.

The Layout Ref provides methods for adding tabs:

Layout Methods Documentation

Example:

layoutRef.current.addTabToTabSet("NAVIGATION", { type: "tab", component: "grid", name: "a grid" });

This adds a new grid component to the tabset with ID "NAVIGATION". (where layoutRef is a React ref to the Layout element; see React Refs).

See External Drag — examples/external-drag/ExternalDrag.tsx and Sticky Button — examples/sticky-button/StickyButton.tsx.

You can handle node events by adding a listener, typically within a component's useEffect hook:

Example:

function MyComponent({ node }) {
  useEffect(() => {
    const listenerId = node.setEventListener("save", () => {
      node.getConfig().subject = subject;
    });
    return () => node.removeEventListener(listenerId);
  }, [subject]);
}

FlexLayout has keyboard operability, ARIA semantics and visible focus styling built in.

Full details — at docs/accessibility.md.

Every element the library renders carries a data-layout-path attribute describing its position in the layout tree — a stable selector for end-to-end tests.

Full details — at docs/testing-your-layout.md.

Tabs can be rendered into external browser windows (useful for multi-monitor setups) by using the enablePopout and enablePopoutIcon attributes. When enabled, a popout icon appears in the tab header. See Popout — examples/popout/Popout.tsx.

Full details — at docs/popout-windows.md.

Many optional properties can be applied to the layout:

Layout Properties Documentation

The JSON model is defined as a set of TypeScript interfaces. See the documentation for details on allowed attributes:

Model Attributes Documentation

Global Attributes Documentation

Row Attributes Documentation

Tabset Attributes Documentation

Note: Tabsets are dynamically created as tabs are moved and deleted when their last tab is removed (unless enableDeleteWhenEmpty is set to false).

Tab Attributes Documentation

Border Attributes Documentation

See Load / Save — examples/localstorage/LocalStorage.tsx for saving/restoring models.

First, install the dependencies:

pnpm install

Run the demo app:

pnpm dev

The pnpm dev command watches for changes in both FlexLayout and the Demo app, allowing you to see updates in your browser immediately.

Run the unit tests with:

pnpm test

Run the playwright tests with:

pnpm playwright

or interactively in the playwright ui with pnpm playwright:ui.

To build the npm distribution, run:

pnpm build