# MAC Address Lookup > Free, private MAC address and OUI vendor lookup. Every prefix page is > pre-rendered static HTML that reads cleanly without JavaScript. No API > keys, no auth. The app itself does no tracking: lookups you make on this > website run client-side and the addresses you enter are never processed > by a server (normal requests still reach the host — a direct link like > /apple carries its URL path). The app sets no cookies. The MCP endpoint > below is the one exception: it is an HTTP request, so a submitted > address is visible to the host. The host (Cloudflare) collects > privacy-first, cookieless, aggregate web analytics. > Run by Jason Tally. > > Privacy policy: https://mac.jasontally.com/privacy — terms of service: https://mac.jasontally.com/terms > — AI assistant usage: https://mac.jasontally.com/help#mcp - [Help & documentation](https://mac.jasontally.com/help): how lookup works, block types, finding your own MAC, FAQ - [Help (Plain text)](https://mac.jasontally.com/help.txt): the same documentation as plain text, for tools that refuse the markdown media type, it is valid Markdown either way - [Help (Markdown)](https://mac.jasontally.com/help.md): the same documentation as Markdown - [Latest OUIs](https://mac.jasontally.com/recent): the most recently registered blocks, refreshed every deploy - Interface available in 31 languages (30 translations plus English; switcher on every page; Urdu, Arabic, and Persian render right-to-left; each language also has a pre-rendered home page under `https://mac.jasontally.com/lang/{locale}/`, declared cross-locale with `hreflang` alternates on all variants) ## URL scheme - `/{hex}` - lookup a MAC address or prefix. 6+ hex characters resolve via longest-prefix match across MA-L, MA-M, MA-S, IAB, and CID; a full 12-hex address resolves to its vendor. Pages are pre-rendered HTML. - `/vendor` - pre-rendered vendor index: every organization with two or more registered blocks, with block and address-space totals, each row linking the organization's page. - `/vendor/{slug}` - pre-rendered provider page: every MAC block registered to one organization (vendors with two or more blocks), as a complete table. - `/country` - pre-rendered country index: every country with at least one registered block, with organization, block, and address-space totals, each row linking the country's page. - `/country/{code}` - pre-rendered country page: every organization with blocks registered in that country, with block counts and address space. - `/former/{name}` - pre-rendered former-owner page: organizations that no longer hold any of their once-registered prefixes, with what happened to each block (transfers, renames, full acquisitions). - `/registry` and `/registry/{type}` - pre-rendered registry-type pages for MA-L, MA-M, MA-S, IAB, and CID. - `/year` and `/year/{year}` - pre-rendered cohorts by first-observed year. - `/region` and `/region/{region}` - pre-rendered continental rollups of current registration countries. - `/history` and `/history/{year}` - observed ownership changes by year. - `/history/country` and `/history/country/{code}` - historical country views of ownership-change records. - `/successor` and `/successor/{slug}` - current owners of transferred prefixes and the former owners they absorbed. - `/{vendor-name}` - free-text search over vendors, former owners, countries, block types, prefixes, and registration years. Results are an HTML table. - `/?q={text}` - legacy query form; redirects to the path scheme. - `/mcp` - stateless MCP server over Streamable HTTP, one `lookup` tool; see below. No JavaScript is required to read any page; results pages for lookups are fully pre-rendered for registered prefixes. ## Data files - https://mac.jasontally.com/data/manifest.json - index of the current data files (Parquet + NDJSON) - [Registry download (NDJSON)](https://mac.jasontally.com/data/registry.ndjson): one JSON object per IEEE assignment (~13.6 MB) - [Lineage download (NDJSON)](https://mac.jasontally.com/data/lineage.ndjson): ownership-change events with first-observed dates, the only public dataset of its kind - https://mac.jasontally.com/data/sources-index.json - raw IEEE source files archived per deploy ## MCP server https://mac.jasontally.com/mcp is a [MCP](https://modelcontextprotocol.io) server over Streamable HTTP. It exposes one tool, `lookup`, which resolves a MAC address or OUI prefix to its registered organization by longest-prefix match. **No API key, no auth, no session, and no handshake required.** The 2026-07-28 specification removed the `initialize` handshake, so a current client posts a request directly. The endpoint also answers an `initialize` probe statelessly — no session is created and no `Mcp-Session-Id` is ever issued — so a 2025-era client can connect too, and a request naming an unsupported protocol version is refused with `-32022` and the list of versions served. Add `https://mac.jasontally.com/mcp` to your client, or read a tool catalog first: {"jsonrpc":"2.0","id":1,"method":"tools/list"} Then resolve one address: POST https://mac.jasontally.com/mcp Content-Type: application/json {"jsonrpc":"2.0","id":1,"method":"tools/call", "params":{"name":"lookup","arguments":{"mac":"8C:1F:64:AF:A4:B2"}}} The reply carries the matched prefix, block type, address count, organization name, registration country, and a link to the record page, which is where the organization address lives. This is the recommended way for an agent to use this site: it returns one resolved answer per call, and never makes the agent read a data file. The machine-readable catalog is at `https://mac.jasontally.com/.well-known/ai-catalog.json`. The registry is also split into small `text/plain` shards under `https://mac.jasontally.com/data/mcp/`, but they are a cache for the server rather than an interface. Each file is one 4-character hex bucket, so a single fetch covers every registered prefix a query could match. Prefer the MCP endpoint. The registry data is derived from the public IEEE Registration Authority registries (no restrictions apply). Ownership-history events come from the runZero mac-tracker dataset (MIT). The app itself ships no ads and no cookies and does no tracking. Lookups run client-side: a lookup you make through the website never sends the address to a server. The MCP endpoint is the one exception, because it is an HTTP request — a submitted address is visible to the host, no session is created, and nothing is linked to anything else. The host (Cloudflare) collects privacy-first, cookieless, aggregate web analytics. The privacy policy is at https://mac.jasontally.com/privacy and the terms of service are at https://mac.jasontally.com/terms. Both state that results can be wrong or out of date, that the site is not affiliated with IEEE, and that results must not be used to identify or profile any individual.