--- layout: default ---

x-client-id

de facto — unregistered request 4 spellings

Declared by 53 providers across 1176 published specification files in the APIs.io network.

What this header is for, and how to use it →

A count here is providers whose published contract declares this header — not providers who send it. Response headers set at the edge rarely appear in an OpenAPI at all, so a low number can measure documentation practice rather than deployment.

Spelled 4 ways

HTTP field names are case-insensitive (RFC 9110 §5.1), so every spelling below is the same header on the wire. A contract is not the wire: generated clients key off the string, and a developer reading two of these sees two different headers.

x-client-idX-Client-IdX-CLIENT-IDX-Client-ID

Providers declaring it (53)

airwallex aldermore att b3 bank-of-ireland-uk bank-of-scotland blockaid bmo bud-co cashfree channel99 chargetrip chase-uk citizens-financial-group cofactr coutts coventry-building-society cynergy-bank egym epa fabric-com first-direct gb-bank gsma hampden-and-co hometrack ikea intelycare investec jp-morgan-chase kroo kyber-network lloyds-banking-group mesh mesh-connect monument-bank netomi nexla open-banking-uk openenvoy oura paragon-bank parseflow plug recognise-bank santander-uk secure-trust-bank shawbrook-bank tandem-bank telkomsel thirdweb tribe-payments visa

Explore

All headers Authentication Guidance on headers.apievangelist.com

Work with this as data

Every header here is available over the APIs.io API and to AI agents over MCP. HTTP Headers is not yet its own endpoint on the v1 API. Reach it through catalog search and the tag graph, or the MCP server.

MCP server

One button, every client — Claude, Cursor, VS Code and the rest.

https://apis.io/mcp

Tools for http headers

3 MCP tools reach this

apis_io_searchSTART HERE — APIs, providers and tags for one query, each with its total.
resolveTurn a domain, URL or GitHub org into the provider it belongs to.
find_cohortsEvery scored population of providers in the catalog.

All 92 tools →

Call it yourself

curl for this page

Search the catalog

curl "https://apis.io/api/v1/search?q=x-client-id&limit=10"

Everything under a tag

curl "https://apis.io/api/v1/tags/x-client-id"

Discovery needs no key. Ratings and market analysis are Pro.

Get an API key

Free tier, no form to fill in. Signing in shares your email address with us — we store it to create your key and to recognise you if you sign in with another provider. See our Privacy Policy and Terms.

GitHub Google LinkedIn

A second provider on the same verified email joins the account you already have.