Why Block

Find out what’s breaking a site, and which privacy tool is doing it.

Designed for the privacy/security conscious user. Why Block assesses what functionality may be limited on a page, and which privacy/security controls may be causing a site to not function properly.

Add to Firefox Download for Brave / Chromium

Version 1.7.0 · Free · Firefox 140+ (on Firefox Browser Add-ons) and Brave or other Chromium-based browsers · How to install

The Why Block toolbar popup listing what's broken on a page: styling, interactive features and video are Broken; page content and images are Probably broken.

Works with

Site broken? Step-by-step guides for each of these.

What it does

Privacy tools stack up: a content blocker, a script blocker, the browser’s own protection, and a filtering DNS. When a site breaks, any of them could be the reason. Why Block watches the page load and tells you which one, and what it broke.

Works for everyone

No blockers or special DNS needed. A plain-language headline says what’s wrong (a server error, a broken certificate, your network blocking the site, or your browser’s own protection) and what you can do about it.

Names the blocker

Every blocked or failed request is traced to its most likely cause: Brave Shields, Firefox Tracking Protection, uBlock Origin, Privacy Badger, NoScript, your DNS filter, or the site itself, with a confidence level.

Shows what’s broken

Missing styles, crashed scripts, videos with nothing to play, empty embeds, missing images, failed logins or captchas, rated from “Broken” to “Blocked as intended”, so you can tell real breakage from tracking you’re glad to lose.

Understands your DNS filter

Checks failing domains with Control-D, NextDNS, AdGuard DNS, AdGuard Home or Pi-hole, explains which rule or list blocks them, and adds an allow rule in one click.

Confirms the culprit

An automatic test in Brave and other Chromium browsers reloads the page with each extension switched off in turn, then switches them back on. Whatever stays blocked with all of them off is Brave Shields. In Firefox, a guided compare does the same.

Domain safety dashboard

One click on the shield next to any domain checks it against security DNS filters, Google Safe Browsing, VirusTotal, Sucuri, abuse.ch, Spamhaus, urlscan.io, AlienVault OTX, PhishStats and more, with a plain-English verdict.

Blocklists, including yours

Threat feeds (Phishing.Database, The Block List Project, DigitalSide, Phishing Army, OpenPhish, Hagezi), popular ad and tracker lists, and any list you add by web address or file.

Encrypted keys

API keys and passwords can be encrypted with AES-256-GCM and unlocked with a passphrase, or in Brave and other Chromium browsers, a passkey (Touch ID, iCloud Keychain, a security key).

Back up & restore

Save your whole setup, including your own lists and, if you like, your keys, to one password-protected file. Restore it in another browser or on another computer.

Observes, never blocks

Why Block doesn’t block or change anything on its own. It only watches what your other tools did, and changes a setting only when you click Allow.

How it works

  1. Open the page that isn’t working. The toolbar badge turns red when blocking is breaking something.
  2. Click the Why Block button. The popup says what’s broken and who blocked it. “Full report” opens the details in the next tab.
  3. Fix it, or leave it. Follow the steps for that blocker, allow the domain in your DNS filter, or run the test to be sure.

Screenshots

Shown with demo sites. Click any image to see it full size.

The full report: what's affected on the page, grouped by area and severity, and which blocker is the most likely cause.
The full report. What’s affected, how badly, and which blocker is most likely responsible.
A blocked image domain: Control-D and Pi-hole both block it; Pi-hole explains it's on an adlist, with an Allow in Pi-hole button.
Why a domain is blocked. Your DNS filter explains the rule or list, and one click allows it.
The domain safety dashboard for a phishing domain: Malicious verdict, with cards from security DNS filters, Google Safe Browsing, VirusTotal, Sucuri, abuse.ch, Spamhaus, urlscan.io, OTX and PhishStats.
Domain safety, security & privacy. Many sources, one verdict, a re-check button on each card.
Settings: Your own lists, with one list added by web address and one uploaded file.
Your own lists. Add blocklists by web address or file.
Settings: DNS filtering, with Control-D and Pi-hole enabled and a provider dropdown.
DNS filtering. Use one provider or several together.
Settings: Key security, encrypted and unlocked, with a passphrase and a passkey registered.
Key security. Encrypted keys, unlocked with a passkey.

Private by design

  • No analytics, no accounts, no servers of ours. Nothing is ever sent to the people who make Why Block.
  • Only domain names, only where you choose. DNS checks and dashboard lookups send a domain name (never the full URL or page content), and only to the providers and sources you’ve switched on.
  • Nothing until you ask. The safety dashboard runs only when you open it. Hovering a shield shows earlier results without a new lookup.
  • Firefox consent built in. In Firefox, online lookups stay off until you agree in Firefox’s own consent prompt. Blocklists are searched locally either way.
  • Your keys stay yours. API keys stay in your browser and go only to their own provider, encrypted with a passkey or passphrase if you turn that on.
  • Short memory. What a tab loaded is kept in memory and cleared when you close the tab.

Install

Firefox

Firefox 140 or later. Installs from Firefox Browser Add-ons and updates automatically.

Add to Firefox

Brave & other Chromium browsers

A download you install yourself, in a few clicks (see below).

why-block-chromium-1.7.0.zip

Works with Chromium-based browsers such as Brave, Chrome, Chromium, Edge, Opera and Vivaldi.

How to install

Firefox

  1. Open Why Block on Firefox Browser Add-ons and click Add to Firefox.
  2. Confirm the permissions prompt. Firefox keeps it up to date automatically.
  3. Already using a copy you installed yourself? Installing from Firefox Browser Add-ons replaces it and keeps your settings, because it’s the same add-on. To be safe, export a backup first (Settings → Back up & restore).

Brave & other Chromium browsers

  1. Unzip the download into a folder you’ll keep.
  2. Open your browser’s extensions page and turn on Developer mode.
  3. Click Load unpacked and choose the folder.
  4. To update later, unzip the new version into the same folder and click reload on the extension. Your settings and passkey carry over.

Extensions page: brave://extensions in Brave, chrome://extensions in Chrome and Chromium, edge://extensions in Edge, opera://extensions in Opera, vivaldi://extensions in Vivaldi.