About

About This Site

7n4.cn is an independently operated networking-technology site that has provided a MAC address vendor lookup service since 2017. The site is not affiliated with the IEEE, Wireshark or any device manufacturer and is maintained by an individual.

Why this site exists

The tool started as a personal need—I was looking up MAC-to-vendor mappings frequently at work and the existing online lookups were either slow or had stale data. So I built one myself: a Rust backend with a prefix-trie index, where lookups are normally resolved in milliseconds, with data auto-synced from the Wireshark official source on a periodic schedule.

Over time it became clear that people wanted more than just the vendor name. They wanted to understand the mechanics behind it—why a phone's MAC doesn't resolve on Wi-Fi, how OUI blocks are assigned, what MAC randomization means for enterprise networks. These answers were scattered across the internet, of varying quality. So in 2024 I started writing a technical blog, organising the knowledge accumulated over the years into systematic articles, published in both English and Chinese.

Who writes this

I'm Jondy, a network engineer with a background in enterprise network operations and security. My day-to-day involves switches, wireless controllers and NAC infrastructure—MAC addresses are inescapable. My writing is practical: not textbook-style concept stacking, but problems and solutions you actually run into. If an article helps you or you disagree with something, get in touch.

What we do

The core of this site is a MAC address and OUI (Organizationally Unique Identifier) lookup tool covering more than 57,000 vendor assignment records. Enter any MAC address to find the hardware vendor behind it.

Alongside the lookup tool, the site maintains a technical blog about network protocols, covering topics such as MAC address fundamentals, the IEEE OUI registry, Wi-Fi and Bluetooth privacy mechanisms, enterprise access control, and device fingerprinting and tracking. The blog articles are originally written, published in both English and Chinese, and are not auto-generated or republished from other sources.

Data sources

The vendor data comes from the publicly available Wireshark manuf file, which our server synchronises automatically every 30 days. Wireshark's data is ultimately sourced from the IEEE Registration Authority.

Technical implementation

Backend: Rust + Axum, prefix-trie index, lookups normally resolved in milliseconds
Frontend: native HTML/CSS, no heavy frameworks, mobile-responsive
Site-wide HTTPS with HSTS and standard security headers

Contact and feedback

For data corrections, feature suggestions or privacy-related requests, please write to us via the Contact Us page. We normally reply within three business days.

MAC Address

A MAC address (Media Access Control Address) is a unique hardware identifier assigned to a network interface at the data link layer, used to identify devices within a local area network.

A standard MAC address is 48 bits long, written as 12 hexadecimal digits:

40:6c:8f:18:2c:03   10-40-F3-AB-4E-C8

For MA-L registrations, the first 24 bits identify the registered organisation. MA-M and MA-S use 28- and 36-bit prefixes. The remaining bits are assigned within the block. A locally administered or randomised address cannot reliably identify a manufacturer.

JSON API

GET /api/mac2vendor?mac=<MAC address>

curl "https://7n4.cn/api/mac2vendor?mac=40:6c:8f:18:2c:03"

{
  "mac": "40:6c:8f:18:2c:03",
  "manuf": "Apple",
  "comment": "Apple, Inc."
}

Returns HTTP 404 when not found: {"error": "vendor not found for MAC ..."}