Who is Header Set for?

Header Set is an open-source project built for web developers and security testers.

Yes — Header Set is open source under the Open Source license and free to use.

What platforms does Header Set run on?

Header Set runs on the web, embeddable surfaces, macOS, Windows, and Linux.

Is Header Set still active?

Unverified. Header Set has not been re-checked since it entered the index, so there is no finding either way — and only a positive finding would say otherwise.

What are alternatives to Header Set?

Similar projects tracked by PulseGate include Header Cleaner, AddHeader, and Request Header Modifier.

Who develops Header Set?

Header Set is developed by 676661.

How long has Header Set been around?

Header Set first shipped in 2026.

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Header Set

Name: Header Set
Author: 676661

mozilla.orgBrowser DevTools & extensions

Header Set is a Firefox extension that counts unique HTTP header names from a pasted request block. It is intended for developers, QA engineers, and security testers who need a quick way to inspect HTTP requests.

Open SourceWebEmbeddablemacOSWindowsLinux

Visit mozilla.org

Overview

5 features

Header Set is a Browser DevTools & extensions project. It focuses on counting unique HTTP header names from request data without manually parsing each header. It is built as an open-source project for web developers and security testers. The project is open source (Open Source). It ships for the web, embeddable surfaces, macOS, Windows, and Linux.

Behind Header Set is 676661, and it first shipped in 2026. Key capabilities include header counting, request parsing, and pasted input. The interface is available in 32 languages, including Czech, German, and Greek.

Summary written by a language model from the project’s public pages.

Header counting
Request parsing
Pasted input
No data collection
Firefox integration

Built with & integrations

Runs on

BrowserEmbeddablemacOSWindowsLinux

Trust & compliance

License

Open Source

Verified signals

HTTPSPrivacy Policy Terms of ServiceOpen SourceFree tierMulti-languageStore-verified publisher

Legal

Indexing history

What PulseGate has recorded for this listing

Indexed4 Sep · 22:38 UTC
Header Set verified via Firefox Add-ons
Source: Firefox Add-ons · Open

Frequently asked questions about Header Set

What is Header Set?: Header Set focuses on counting unique HTTP header names from request data without manually parsing each header. It is catalogued under Browser DevTools & extensions on PulseGate.
Who is Header Set for?: Header Set is an open-source project built for web developers and security testers.
Is Header Set free?: Yes — Header Set is open source under the Open Source license and free to use.
What platforms does Header Set run on?: Header Set runs on the web, embeddable surfaces, macOS, Windows, and Linux.
Is Header Set still active?: Unverified. Header Set has not been re-checked since it entered the index, so there is no finding either way — and only a positive finding would say otherwise.
What are alternatives to Header Set?: Similar projects tracked by PulseGate include Header Cleaner, AddHeader, and Request Header Modifier.Header Cleaner AddHeader Request Header Modifier
Who develops Header Set?: Header Set is developed by 676661.
How long has Header Set been around?: Header Set first shipped in 2026.

At a glance

Pricing: Open Source
Platforms: Web
License: Open Source
First seen: 4 Sep 2026
Built for: web developers and security testers
Model: Open source
Solves: Counting unique HTTP header names from request data without manually parsing each header.

Registered as

Firefox Add-ons: header-set

Developer

676661

Index record

Indexed: 4 Sep 2026
Lifecycle: Alive
First seen: Sep 2026
Last seen: 4 Sep 2026

Identity audit (13)

Slug: header-set-mozilla-org
Lifecycle last checked: 8 Sep 2026
Verification state: Indexed for public listing
Listing state: Listed: yes
Index status: Included in index
Latest evidence snapshot: 4 Sep 2026
Timeline basis: Indexed-at chronology (no inferred launch/funding milestones).
Name from: Derived from the project's own page and URL.
Category from: Assigned by a language model.
Summary from: Written by a language model from public pages.
Languages from: Detected by a language model, checked against the page's own declaration.
Last updated: 4 Sep 2026
Canonical URL: https://addons.mozilla.org/en-US/firefox/addon/header-set

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