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Split views are experimental in Firefox. There will be bugs and the API may change. This feature requires Firefox’s native split view support which is still under development.
Glide Browser provides access to Firefox’s experimental split view feature, allowing you to display multiple tabs side-by-side in a single window.

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Overview

Split views let you:
  • View two or more tabs simultaneously
  • Compare content across tabs
  • Work with multiple pages at once
  • Create custom multi-pane layouts
Before using split views, users must acknowledge the experimental nature by setting browser.tabs.splitview.hasUsed preference. Glide handles this automatically on first use.

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API Access

Split views are available through the unstable API: 
glide.unstable.split_views

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Creating Split Views

Create a split view with at least 2 tabs: 
// Get some tabs
const tabs = await glide.tabs.query({});

// Create split view with tab objects
const splitView = glide.unstable.split_views.create([tabs[0], tabs[1]]);

console.log(splitView.id);     // Unique split view ID
console.log(splitView.tabs);   // Array of tabs in split view

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Using Tab IDs

You can also pass tab IDs directly: 
const tabs = await glide.tabs.query({});
const splitView = glide.unstable.split_views.create([
  tabs[0].id!,
  tabs[1].id!
]);

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Custom Split View ID

Specify a custom ID for the split view: 
const splitView = glide.unstable.split_views.create(
  [tab1, tab2],
  { id: 1234 }
);

console.log(splitView.id); // 1234
Custom IDs must be unique. Creating a split view with an ID that’s already in use will throw an error:
Error: Could not create a splitview; The 1234 ID is already in use

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Retrieving Split Views

Get a split view by various identifiers: 
// By split view ID
const splitView = glide.unstable.split_views.get(splitViewId);

// By tab ID
const splitView = glide.unstable.split_views.get(tabId);

// By tab object
const splitView = glide.unstable.split_views.get(tab);

if (splitView) {
  console.log(`Split view ${splitView.id} has ${splitView.tabs.length} tabs`);
}

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Checking Split View Status

Check if a tab is in a split view: 
const tab = await glide.tabs.active();

if (glide.unstable.split_views.has_split_view(tab)) {
  console.log("Current tab is in a split view");
} else {
  console.log("Current tab is standalone");
}

// Also works with tab ID
if (glide.unstable.split_views.has_split_view(tab.id!)) {
  // Tab is in split view
}

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Separating Tabs

Revert a tab from a split view back to a normal tab: 
// Separate by tab object
glide.unstable.split_views.separate(tab);

// Separate by tab ID
glide.unstable.split_views.separate(tabId);

// Separate by split view ID (closes entire split view)
glide.unstable.split_views.separate(splitViewId);
When you separate a tab from a split view, all tabs in that split view are reverted to normal tabs.

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Split View Object

The split view object has the following structure: 
interface SplitView {
  id: number;                    // Unique split view identifier
  tabs: Browser.Tabs.Tab[];      // Array of tabs in the split view
}

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Practical Examples

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Toggle Split View

glide.keymaps.set("normal", "<leader>s", async () => {
  const tabs = await glide.tabs.query({});
  
  // Need at least 2 tabs
  if (tabs.length < 2) {
    console.log("Need at least 2 tabs for split view");
    return;
  }

  const currentTab = tabs.find(t => t.active);
  
  // Check if already in split view
  if (currentTab && glide.unstable.split_views.has_split_view(currentTab)) {
    // Separate current tab
    glide.unstable.split_views.separate(currentTab);
  } else {
    // Create split view with first two tabs
    glide.unstable.split_views.create([tabs[0], tabs[1]]);
  }
});

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Split View with Specific Tabs

glide.keymaps.set("normal", "<leader>2", async () => {
  // Prompt user to select tabs (simplified example)
  const tab1 = await glide.tabs.get_first({ index: 0 });
  const tab2 = await glide.tabs.get_first({ index: 1 });
  
  if (tab1 && tab2) {
    const splitView = glide.unstable.split_views.create([tab1, tab2]);
    console.log(`Created split view ${splitView.id}`);
  }
});

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Open URLs in Split View

async function openInSplitView(url1: string, url2: string) {
  // Open two new tabs
  const tab1 = await browser.tabs.create({ url: url1, active: false });
  const tab2 = await browser.tabs.create({ url: url2, active: false });
  
  // Wait for tabs to be ready
  await new Promise(resolve => setTimeout(resolve, 100));
  
  // Create split view
  return glide.unstable.split_views.create([tab1.id!, tab2.id!]);
}

// Usage
glide.keymaps.set("normal", "<leader>d", async () => {
  await openInSplitView(
    "https://developer.mozilla.org",
    "https://glide-browser.app/docs"
  );
});

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Compare Tabs Side-by-Side

glide.excmds.create(
  { 
    name: "split_compare",
    description: "Compare current tab with another"
  },
  async () => {
    const currentTab = await glide.tabs.active();
    const allTabs = await glide.tabs.query({});
    
    // Find another tab (not current)
    const otherTab = allTabs.find(t => t.id !== currentTab.id);
    
    if (otherTab) {
      glide.unstable.split_views.create([currentTab, otherTab]);
    } else {
      console.log("Need at least one other tab to compare");
    }
  }
);

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Limitations and Restrictions

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Pinned Tabs

You cannot create split views with pinned tabs. Attempting to do so will throw an error:
Error: Could not create a splitview; Is one of the tabs pinned?
Unpin tabs before adding them to a split view: 
const tab = await glide.tabs.active();

if (tab.pinned) {
  await browser.tabs.update(tab.id, { pinned: false });
}

// Now can create split view
glide.unstable.split_views.create([tab, otherTab]);

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Minimum Tabs

You must provide at least 2 tabs to create a split view.

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Browser Support

Split views require:
  • Firefox with experimental split view feature enabled
  • Glide Browser (which enables this automatically)

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Known Issues

As an experimental Firefox feature, you may encounter:
  • Rendering issues when resizing
  • Tab bar display problems
  • Incorrect focus handling
  • Tabs may not always reflect split view state immediately
  • Closing tabs in a split view may have unexpected behavior
  • Multiple rendered tabs consume more memory
  • Complex pages may affect scrolling smoothness

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Debugging

Check split view state in the console: 
// List all tabs and their split view status
const tabs = await glide.tabs.query({});
for (const tab of tabs) {
  const inSplit = glide.unstable.split_views.has_split_view(tab);
  const splitView = glide.unstable.split_views.get(tab);
  
  console.log(`Tab ${tab.id}: ${inSplit ? 'in split view ' + splitView?.id : 'standalone'}`);
}

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Future Improvements

The split view API is under active development. Potential future enhancements:
  • More than 2 tabs per split view
  • Customizable split orientations (horizontal/vertical)
  • Split view layouts and configurations
  • Better integration with tab management
The split view API is defined in glide.d.ts:897-929. Test examples can be found in test/split-views/browser_split_views.ts:13-146.

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Cleanup

When testing split views, you may want to clean up the preference: 
glide.prefs.clear("browser.tabs.splitview.hasUsed");