DNS Quick Toggle — Firefox Edition

A lightweight Firefox/Mullvad Browser extension to manage and switch between DNS-over-HTTPS (DoH) providers instantly from the toolbar.

Features

• One-click switching between saved DoH providers
• Clipboard auto-copy — activating a provider copies its URL automatically
• Toolbar badge showing the active provider's initials (e.g. MU for Mullvad)
• Add/remove custom providers
• 8 providers pre-loaded (Mullvad, Cloudflare, NextDNS, Quad9, AdGuard, Control D)
• Disable DoH button to revert to browser default
• Tested on Firefox 90+ and Mullvad Browser

Installation

Temporary (development)

1. Open about:debugging#/runtime/this-firefox
2. Click Load Temporary Add-on
3. Select the manifest.json file from the extension folder

Note: Temporary add-ons are removed when Firefox closes. For persistent install, use web-ext.

Permanent (via web-ext)

npm install -g web-ext
cd dns-toggle-firefox/
web-ext build
# Outputs a .xpi file in web-ext-artifacts/

Then install the .xpi via about:addons → gear icon → Install Add-on From File.

Usage

1. Click the DNS Quick Toggle icon in the toolbar
2. Click any provider to:
   • Mark it as active (green dot + badge update)
   • Auto-copy its DoH URL to clipboard
3. Open about:preferences#privacy → scroll to DNS over HTTPS
4. Paste the copied URL into the custom resolver field
5. Done — your DoH is set

To disable DoH entirely, click ⊘ Disable DoH.

Pre-loaded Providers

Provider	URL	Tag
Mullvad	https://doh.mullvad.net/dns-query	no-log
Mullvad (adblock)	https://adblock.doh.mullvad.net/dns-query	adblock
Mullvad (extended)	https://extended.doh.mullvad.net/dns-query	adblock+
Cloudflare	https://cloudflare-dns.com/dns-query	—
Cloudflare (security)	https://security.cloudflare-dns.com/dns-query	malware
NextDNS	https://dns.nextdns.io	—
Quad9	https://dns.quad9.net/dns-query	malware
AdGuard	https://dns.adguard-dns.com/dns-query	adblock
Control D	https://freedns.controld.com/p0	—

Adding a Custom Provider

1. Enter a name (e.g. My NextDNS)
2. Enter the DoH URL (must start with https://)
3. Click Add

Custom providers are saved in extension storage and persist across sessions.

Why Not Automatic Switching?

Firefox's browserSettings.customEngineURL API — which would allow programmatic DNS changes — is intentionally disabled in Mullvad Browser for privacy hardening reasons. As a result, this extension manages your provider list and clipboard; you apply the change once in browser settings.

The one-time paste workflow is intentional: it avoids requiring elevated browser permissions and keeps the extension's footprint minimal.

File Structure

dns-toggle-firefox/
├── manifest.json       # MV2 extension manifest
├── background.js       # Badge management (no DNS API calls)
├── popup.html          # Extension popup UI
├── popup.js            # All logic — no background messaging
└── icons/
    ├── icon16.png
    ├── icon48.png
    └── icon128.png

Permissions

Permission	Reason
storage	Save provider list and active selection
tabs	Open about:preferences#privacy on click
browserSettings	Badge color (gracefully ignored if unavailable)
dns	Reserved for future use