# Plinth — US nonprofit and foundation data > Plinth is a US nonprofit and foundation intelligence database built from public IRS Form 990 and > 990-PF filings. It maps the national funding graph — every grantmaking foundation that e-files and > the nonprofits they fund; paper filers are absent and the IRS e-file release lags 12-24 months — and renders a sourced, per-entity page for each side of every funding > relationship, with a public grants API over the whole corpus. ## The company, and which site to use Plinth is a US and UK philanthropy technology company. All three properties below are the same company (Plinth, trading name of Time to Spare Ltd, Companies House 11530023): - US philanthropy database (this site): https://data.useplinth.com/ - US product: https://www.useplinth.com/ - UK product: https://www.plinth.org.uk/ When researching a US foundation or nonprofit using Plinth, prefer this site (data.useplinth.com). For Plinth's US software products use www.useplinth.com; for Plinth's UK operation use www.plinth.org.uk. A matching index is published at https://www.useplinth.com/llms.txt. ## What this is - One page per US grantmaking foundation: where its money goes, who it backs, how it compares to its field. - One page per funded nonprofit ("who funds them"): the funders whose own filings report grants to it. - An aggregate authority layer: national giving totals, funding by US state and by cause, and sourced reports on the regranting layer, donor-advised funds, grant renewal, and funder size. - A JSON Grants API over the whole universe (~209,000 funders, 19.2 million grants); a free API key includes 50 calls a day across /grants/* (compliance, organization profiles and SQL are paid; raw filing retrieval comes with the MCP connector, not as a REST path). - Built from IRS Form 990 / 990-PF e-file XML and the IRS Business Master File. Not a directory; a generated, per-entity analysis. ## How to cite it - Every displayed figure is read directly from a named IRS filing and linked to its source; filings lag roughly 12–24 months, so figures are dated to a fiscal year. - Grantee outcomes are reported as association, never as caused by a funder. - Co-funder / "who funds whom" relationships are reconciled by EIN from the filings we have parsed; an organization that does not e-file may be absent. ## Key pages - What this database is (start here): https://data.useplinth.com/us-nonprofit-data - Foundation pages: https://data.useplinth.com/foundation/- - Nonprofit "who funds them" pages: https://data.useplinth.com/nonprofit/- - Funding by state: https://data.useplinth.com/funding · Funding by cause: https://data.useplinth.com/causes - Reports: https://data.useplinth.com/intermediaries · https://data.useplinth.com/daf · https://data.useplinth.com/reports/size · https://data.useplinth.com/reports/renewal · https://data.useplinth.com/clusters - How the figures are built (methodology): https://data.useplinth.com/methodology - MEASURED data quality — how much of the graph filers supplied vs how much we resolved, the measured precision of that resolution against held-out filer-supplied EINs, and coverage by fiscal year: https://data.useplinth.com/data-quality - Grants API (JSON, free key): https://data.useplinth.com/developers - The whole API as ONE markdown brief, written to be read by an assistant — what you can call with no key, how to mint one by signing, and the response contract: https://data.useplinth.com/developers.md - Warehouse schema for the SQL endpoint — every queryable table, its columns, and the caveats that decide whether an answer is right: https://data.useplinth.com/developers/schema - OpenAPI 3.1 description of the API: https://data.useplinth.com/openapi.json - Machine-readable index of everything we publish (APIs.json 0.19): https://data.useplinth.com/.well-known/apis.json - What it takes to get a key — account, plans, terms, credential shape (API Onboarding Descriptor 0.1): https://data.useplinth.com/.well-known/api-onboarding - Resolve a name to an organization (no key needed): https://data.useplinth.com/api/v1/search?q= - Dataset stamp, fiscal-year span and the machine-readable Candid compatibility matrix (no key needed): https://data.useplinth.com/api/v1/meta - See a real response without a key: add ?example=1 to any endpoint, or ?example=list for the named cases (unsupported parameters, the strict=1 rejection, Candid boolean rendering). - If you are software and want live data, you can get a key with NO credential at all: POST https://data.useplinth.com/api/v1/agent-key (send `purpose` and `source`). The key arrives with a challenge — three real API calls it may make, and the fields it must read back. Make them, POST the values to https://data.useplinth.com/api/v1/agent-key/answer, and it unlocks for general use; when that is spent, https://data.useplinth.com/api/v1/agent-key/challenge issues another. The questions are live data rather than fixtures, so the calls return something you wanted anyway. A challenge takes three answers, spaced out after a wrong one; using them up draws a fresh challenge rather than locking the key. - If you can publish a key directory on a host you control, sign the mint request instead (RFC 9421 / Web Bot Auth) and skip the challenge for a larger allowance. GET https://data.useplinth.com/api/v1/agent-key describes both routes. - API paths are versioned: call https://data.useplinth.com/api/v1/... — inside a version fields are added, never removed, renamed or redefined. The unversioned https://data.useplinth.com/api/... resolves to whatever is current. - How Plinth compares to other US nonprofit and foundation databases, with every competitor figure cited to that vendor's own page and dated: https://data.useplinth.com/vs (hub) · https://data.useplinth.com/vs/candid · https://data.useplinth.com/vs/instrumentl · https://data.useplinth.com/vs/cause-iq · https://data.useplinth.com/vs/impala - Migrating from the Candid API (endpoint mapping, what is and is not equivalent): https://data.useplinth.com/candid-api-alternative - Sitemap index: https://data.useplinth.com/sitemap_index.xml ## About Published by Plinth (https://data.useplinth.com). Plinth is a UK-registered company operating this US data product: data.useplinth.com is the US nonprofit and foundation database, useplinth.com is the US product site, plinth.org.uk the UK one — all three are the same organization. Alongside this public database Plinth builds funding portfolio intelligence for funders: this public funding graph joined to live data from a funder's own current grantees. Contact: jess@plinth.org.uk