Trades on 1 secondary market

Castle

Castle is a fraud and account-abuse prevention platform that stops bots, credential stuffing, account takeover, and multi-accounting through behavioral analysis and device fingerprinting — without CAPTCHAs or puzzles for legitimate users. Developers integrate a client-side SDK (browser and mobile) t

developing 44.0 / 100 1 API View provider profile →
CompanySecurityFraud PreventionBot DetectionDevice FingerprintingAccount Takeover

Castle is an API provider whose private shares are listed on 1 secondary market: Nasdaq Private Market.

Castle publishes 1 API indexed on the APIs.io network.

Where It Trades

N Nasdaq Private Market View listing →

Listing data is compiled from the public marketplace pages of Forge Global, Hiive, EquityZen, Nasdaq Private Market, and Augment. A listing indicates that a venue has published a page for this company — it is not an offer, a quote, or investment advice, and APIs.io has no affiliation with any venue.

Work with this as data

Every listing here is available over the APIs.io API and to AI agents over MCP. Secondary Market 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 secondary market

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=castle&limit=10"
Everything under a tag 
curl "https://apis.io/api/v1/tags/castle"

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