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Overview

The glide.prefs API provides methods for reading and writing Firefox preferences (about:config settings). This allows you to customize Firefox behavior directly from your glide.ts configuration file, eliminating the need for a separate prefs.js file.
Firefox preferences are low-level settings that control browser behavior. You can view all preferences by navigating to about:config in Firefox.Learn more about about:config

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Methods

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set()

Set a preference value. 
glide.prefs.set(
  name: string,
  value: string | number | boolean
): void
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name
string
required
The name of the preference to set. This should be a valid Firefox preference key.
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value
string | number | boolean
required
The value to set. The type must match the preference’s expected type:
  • Boolean preferences accept true or false
  • Integer preferences accept numbers
  • String preferences accept strings
Important Notes:
  1. Top-level only: This function is expected to be called at the top-level of your config. Calling it in callbacks may not properly apply the preference everywhere.
  2. Restart may be required: Some preferences require a browser restart to take effect.
  3. No type checking: There is no validation that the preference name exists or that the value type is correct. Invalid preferences will be silently ignored.

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get()

Get the value of a preference. 
glide.prefs.get(
  name: string
): string | number | boolean | undefined
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name
string
required
The name of the preference to retrieve.
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return
string | number | boolean | undefined
The preference value, or undefined if the preference is not defined. The return type matches the preference’s actual type.

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clear()

Reset a preference to its default value. 
glide.prefs.clear(name: string): void
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name
string
required
The name of the preference to reset.
After calling clear(), the preference will return to its Firefox default value. If the preference was user-defined (not a built-in Firefox preference), it will be removed entirely.

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scoped()

Create a scoped preferences manager for temporary preference changes. 
glide.prefs.scoped(): glide.ScopedPrefs
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return
glide.ScopedPrefs
A scoped preferences object that supports:
  • set(name, value): Set a temporary preference
  • get(name): Get a preference value
  • clear(name): Clear a temporary preference
  • Automatic cleanup when the scope exits (via Symbol.dispose)
You must use the using keyword when assigning the scoped preferences object:
using prefs = glide.prefs.scoped(); // ✓ Correct
const prefs = glide.prefs.scoped(); // ✗ Wrong - won't auto-restore
The using keyword ensures preferences are automatically restored when the scope exits, even if an error occurs.
Scoped preferences are determined by the lifetime of the return value. When the scoped object goes out of scope (block ends, function returns, etc.), all preferences are automatically restored to their previous values.

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Buffer-Specific Preferences

You can also set preferences that apply only to the current buffer (tab) using glide.buf.prefs: 
// Set a preference for the current tab only
glide.buf.prefs.set('layout.css.devPixelsPerPx', 1.5);

// When navigating to a new tab, the preference is reset
Global Prefs (glide.prefs):
  • Apply browser-wide
  • Persist across all tabs and windows
  • Survive browser restarts (if set in config)
Buffer Prefs (glide.buf.prefs):
  • Apply only to the current tab
  • Reset when navigating to a different tab
  • Useful for tab-specific customizations

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Complete Examples

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Custom Browser Behavior

glide.ts
// Disable tab animations
glide.prefs.set('browser.tabs.animate', false);

// Don't close window when closing last tab
glide.prefs.set('browser.tabs.closeWindowWithLastTab', false);

// Don't warn when closing multiple tabs
glide.prefs.set('browser.tabs.warnOnClose', false);
glide.prefs.set('browser.tabs.warnOnCloseOtherTabs', false);

// Set minimum tab width
glide.prefs.set('browser.tabs.tabMinWidth', 50);

// Disable pocket
glide.prefs.set('extensions.pocket.enabled', false);

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Developer Settings

glide.ts
// Enable browser toolbox
glide.prefs.set('devtools.chrome.enabled', true);
glide.prefs.set('devtools.debugger.remote-enabled', true);

// Enable userChrome.css
glide.prefs.set('toolkit.legacyUserProfileCustomizations.stylesheets', true);

// Disable cache during development
glide.prefs.set('browser.cache.disk.enable', false);
glide.prefs.set('browser.cache.memory.enable', false);

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Privacy & Security

glide.ts
// Enhanced tracking protection
glide.prefs.set('privacy.trackingprotection.enabled', true);
glide.prefs.set('privacy.trackingprotection.socialtracking.enabled', true);

// Disable telemetry
glide.prefs.set('toolkit.telemetry.enabled', false);
glide.prefs.set('datareporting.healthreport.uploadEnabled', false);

// HTTPS-only mode
glide.prefs.set('dom.security.https_only_mode', true);

// Disable WebRTC (prevents IP leaks)
glide.prefs.set('media.peerconnection.enabled', false);

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Dynamic Preference Toggle

glide.ts
function togglePref(name: string, trueValue: any = true, falseValue: any = false) {
  const current = glide.prefs.get(name);
  const newValue = current === trueValue ? falseValue : trueValue;
  glide.prefs.set(name, newValue);
  return newValue;
}

glide.keymaps.set('normal', '<leader>ta', () => {
  const state = togglePref('browser.tabs.animate');
  console.log('Tab animations:', state ? 'enabled' : 'disabled');
});

glide.keymaps.set('normal', '<leader>tm', () => {
  const state = togglePref('ui.prefersReducedMotion', 1, 0);
  console.log('Reduced motion:', state === 1 ? 'enabled' : 'disabled');
});

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Common Preferences Reference

Tab Behavior
  • browser.tabs.closeWindowWithLastTab - Close window when last tab closes
  • browser.tabs.warnOnClose - Warn when closing multiple tabs
  • browser.tabs.tabMinWidth - Minimum tab width (pixels)
  • browser.tabs.animate - Enable tab animations
UI & Appearance
  • ui.prefersReducedMotion - Reduce animations (0=off, 1=on)
  • layout.css.devPixelsPerPx - UI scale factor
  • toolkit.legacyUserProfileCustomizations.stylesheets - Enable userChrome.css
Privacy
  • privacy.trackingprotection.enabled - Enable tracking protection
  • network.cookie.cookieBehavior - Cookie policy (0=accept all, 1=reject third-party, etc.)
  • dom.security.https_only_mode - HTTPS-only mode
Performance
  • browser.cache.disk.enable - Disk cache
  • browser.cache.memory.enable - Memory cache
  • browser.sessionstore.interval - Session save interval (milliseconds)
Developer
  • devtools.chrome.enabled - Enable browser toolbox
  • devtools.debugger.remote-enabled - Enable remote debugging
For a complete list, see about:config in Firefox.

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Type Reference

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glide.ScopedPrefs

type ScopedPrefs = Omit<typeof glide.prefs, 'scoped'> & {
  [Symbol.dispose](): void;
};
A scoped preferences manager that automatically restores preferences when disposed. Must be used with the using keyword.