About our data

The primary source: SEC Form NPORT-P

Every US-registered investment company — ETFs, mutual funds, closed-end funds — is required to file Form NPORT-P with the Securities and Exchange Commission each quarter. These filings disclose the fund's complete holdings as of the end of the reporting period: every security held, its value, its weight as a percentage of net assets, and its identifier (CUSIP, ISIN, or ticker).

NPORT-P filings are public, free, and available through SEC EDGAR. OpenBell uses no third-party data vendors for holdings data. Every comparison page links directly to the source filing so you can verify any number in seconds.

The NPORT-P specification is defined by the SEC and covers the following fields that we use in overlap analysis:

• Security name, CUSIP, ISIN, ticker
• Fair value in USD and percentage of net assets
• Asset category (equity, debt, short-term investments, derivatives, etc.)
• Country of issuer, sector classification (where reported), currency
• Fund-level total net assets and number of holdings

The 60-day lag explained

NPORT-P filings become public approximately 60 days after the end of the quarter being reported. This means Q1 data (January–March) is publicly available around the end of May.

This is a regulatory disclosure delay, not a limitation of OpenBell. All professional services face the same lag for mutual fund and closed-end fund data. ETF issuers publish daily holdings on their own websites, but we deliberately use only NPORT-P data so that all fund types are analyzed on the same basis — mixing daily ETF data with quarterly mutual fund data would make cross-fund comparisons misleading.

Supporting data sources

We supplement NPORT-P holdings data with two additional public sources:

What we don't cover

• Bond funds (v1): Meaningful overlap on individual bond CUSIPs requires exposure-based analysis (issuer, duration, credit quality), not CUSIP matching. Planned for v2.
• Money market funds: Overlap isn't a meaningful concept for money market funds. Excluded.
• Hedge funds and private funds: These don't file NPORT-P publicly.
• Foreign-domiciled funds: UCITS, SICAV, and similar non-US structures don't file NPORT-P.
• Real-time prices: We deliberately don't show real-time prices.

How the pipeline works

Each day, we check the SEC for newly published fund filings. When a new quarterly report comes in, we read the holdings it contains, run checks to make sure the data is complete and makes sense, and make it available on OpenBell. Most funds show up within 24 hours of their filing going public.

When you run a comparison, all the number-crunching happens directly in your browser — nothing is sent to an OpenBell server. Your browser pulls the holdings data for each fund and computes the results locally.