What is the Open Cap Table Format?

The problem it was created to solve

For most of the last two decades, a cap table's shape was decided by whichever platform happened to hold it. Each vendor invented its own idea of what a share class was, how a SAFE should be recorded, and what a vesting schedule looked like in a database. The consequence was predictable: moving between systems meant rebuilding the record by hand, and every migration was an opportunity to lose history.

That mattered more than it sounds. A cap table is not a spreadsheet of current percentages. It is the accumulated consequence of every financing, grant, conversion and transfer a company has ever executed. Lose the events and you keep the numbers while losing the ability to prove them, which is exactly the thing an investor, an auditor or an underwriter needs.

What the schema actually contains

OCF is a set of typed objects. Each one has required fields and defined relationships to the others, which is what makes a file readable without human interpretation.

What one event looks like

Here is a single stock issuance as OCF represents it. The class and holder are object references; quantity and price are typed values; the authorizing board consent is named so another system can resolve it.

{
  "object_type": "TX_STOCK_ISSUANCE",
  "id": "issuance-northwind-0042",
  "date": "2026-03-04",
  "security_id": "sec-series-b-0117",
  "stakeholder_id": "stakeholder-ridgeline-ventures",
  "stock_class_id": "class-series-b-preferred",
  "stock_legend_ids": ["legend-standard-preferred"],
  "quantity": "1250000",
  "share_price": { "amount": "2.84", "currency": "USD" },
  "consideration_text": "Cash",
  "comments": ["Authorized by board consent dated 2026-03-01 (document_id: doc-board-consent-2026-03)"]
}

A spreadsheet row would tell you Ridgeline owns 1,250,000 shares. This tells you when they got them, at what price, of which class, and under what authority, in a form a machine can check.

Who maintains it

The Open Cap Table Coalition, a nonprofit industry body, maintains the schema and publishes it openly on GitHub. Work is underway to establish the Coalition as a Linux Foundation project, so the standard outlives any single company, including the ones that helped write it.

The standard was established with the institutions and law firms that handle trillions in equity: among them Morgan Stanley, Fidelity, Nasdaq Private Market, Cooley, Fenwick, Goodwin, Gunderson Dettmer, Orrick, Perkins Coie and Wilson Sonsini. That matters for a practical reason rather than a reputational one: when your counsel already reads the format, sending them OCF is faster than sending them a spreadsheet and a phone call.

Coalition membership reflects participation in an industry standard and does not imply endorsement of CaptableAI by any other member.

Format, protocol, and why the distinction matters

A format lets two systems exchange a file. A protocol lets many participants act on the same record without anyone needing a private copy of it. OCF is the first; the Open Cap Table Protocol is the second, and it implements OCF onchain with a registered transfer agent as system operator.

Conformance is not the same as correctness

This is the part most explanations skip. A file can validate perfectly against the schema and still describe a cap table that is wrong. Conformance says the shape is right; it says nothing about whether the numbers reconcile or whether the events happened in the order recorded.

A record worth showing an investor has to pass both. In practice that means four things beyond schema validation:

Common questions

Nothing here is legal, tax or investment advice. OCF is maintained by the Open Cap Table Coalition; this page is our explanation of it, not an official Coalition publication.