# NSC Blocker

> The NSC response header defines how websites can communicate that their content isn't safe, for example when it contains adult content. The header is defined in an experimental specification and implemented on the client side with this add-on.

Canonical page: [https://chrome-stats.com/d/nsc-blocker](https://chrome-stats.com/d/nsc-blocker)

## Overview

- **ID:** `nsc-blocker`
- **Platform:** Firefox
- **Type:** Firefox add-on
- **Status:** Available
- **Publisher:** Safe Internet Initiative
- **Category:** privacy-security
- **Rating:** 5.00 / 5 (1 ratings)
- **Version:** 1.2
- **Last updated:** 2022-03-29
- **First published:** 2022-03-26
- **Size:** 100 KB
- **Data as of:** 2026-09-14
- **Store listing:** [Firefox Add-ons Store](https://addons.mozilla.org/firefox/addon/nsc-blocker/)
- **Website:** [https://gitlab.com/Safe-Internet-Initiative/nsc-blocker](https://gitlab.com/Safe-Internet-Initiative/nsc-blocker)

## Description

NSC Blocker is a Firefox add-on that implements blocking and statistics for NSC headers. It allows you to try out the new specification and analyze whether your own websites implement the specification correctly.

## Rankings

- #130,035 — Overall

## Permissions and access

### Permissions

- `webRequest`
- `webRequestBlocking`
- `storage`
- `<all_urls>`

## Safety

- **Risk impact:** Moderate risk impact
- **Risk likelihood:** Low risk likelihood

### Analysis details

- Allows access to all websites, posing a significant security risk as it can monitor and modify data from any visited site.
- This extension has low user count. Unpopular extensions may not be stable or safe.

> Some risk analysis details are omitted from this free response. [Upgrade to view the full analysis](https://chrome-stats.com/pricing).

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Source: [Chrome-Stats](https://chrome-stats.com/d/nsc-blocker)