# XBRL

Also written iXBRL.

*https://stockmarketstack.com/glossary/xbrl · next to Fundamental Data & Stock Research Platforms*

**Definition:** XBRL is the tagging standard that turns a filed financial statement into machine-readable facts: each number carries an element name, a period, a unit and a set of dimensions. It makes filings parseable, not comparable — issuers pick elements from a large taxonomy and invent their own where none fits, so the same line item arrives under different tags at different companies.

## How it works

A filing marked up in XBRL is not a spreadsheet of labelled numbers. It is a set of *facts*, and a
fact has four parts: an element from a taxonomy (the concept — what the number is), a context (which
entity and which instant or period it covers), a unit, and optionally one or more dimensions that
narrow it further. "Revenue" is not a number. It is a concept against which a filer has reported
several facts — a year, four quarters, a restated prior year, and a dimensional breakdown by product
line or geography — and pulling "the" revenue out means choosing among them.

The markup used to travel beside the document. Under the current regime it travels *inside* it:
inline XBRL embeds the tags in the same HTML file a person reads, so there is one artefact rather
than a human-readable document plus a machine-readable exhibit that could quietly disagree. The
SEC's staff interpretations record that all relevant phase-in periods for operating company
financial statements and fund prospectuses ended in September 2021. Europe went the same way for a
different reason: under the European Single Electronic Format, listed issuers tag IFRS consolidated
statements in inline XBRL against a taxonomy ESMA updates annually, most recently with the 2025 IFRS
taxonomy.

## Where standardisation stops

**Extension elements.** A filer that cannot find a suitable element in the standard taxonomy creates
its own. That is permitted and sometimes correct, and it is also where comparability goes. The SEC's
sample comment letter on XBRL disclosures asks companies why they used a custom tag where an
existing US GAAP element would have served, and asks separately why the element used for the same
line item changed between periods. Both questions exist because both happen.

**Dimensions.** The same staff guidance tells filers to use the predefined tables and axes as they
exist in the US GAAP taxonomy, and says creating new hypercubes and dimensions should generally be
avoided. The advice is not always taken, and a consumer who ignores dimensions altogether will sum
a total together with the slices that already compose it.

**Mechanical errors.** The staff letter also notes shares outstanding tagged with materially
different values on the cover page and in the balance sheet because the two were scaled
differently. A tagged number is not a verified number.

## What the SEC's own layers flatten

Two free surfaces read the tags for you, and each gives something up. The XBRL APIs return facts by
company or by concept, and the `frames` endpoint assembles one concept across filers by taking the
fact last filed that most closely fits the period — a mix of vintages rather than a snapshot, which
is the [point-in-time](https://stockmarketstack.com/glossary/point-in-time) problem wearing a convenient interface. The
Financial Statement Data Sets go the other way: published per filing and presented as filed, with no
standardisation applied, which makes them usable for reconstructing what was reported and useless as
a comparable panel straight out of the box. [How to get SEC filings as
data](https://stockmarketstack.com/how-to/get-sec-filings-as-data) covers both endpoints and their limits.

## Why it matters here

The practical consequence is the one that costs money: **two vendors reading the same filing
legitimately produce different fields.** Every step between the markup and a column in an API
response is a judgement — which element counts as the headline figure, whether a company's extension
maps onto a standard line or is dropped, which dimensional slice is "the" segment, what to do when
the filer changed elements in the third year of the series. None of that is visible in the response,
and none of it is wrong.

So the question to ask a fundamentals vendor is not whether it uses XBRL. It is what happens to the
parts XBRL does not settle. [SEC EDGAR](https://stockmarketstack.com/tools/sec-edgar) hands you the facts and no opinion, free
and keyless, and the assembly is yours. [sec-api.io](https://stockmarketstack.com/tools/sec-api-io) sells the conversion and the
section extraction. [SEC EDGAR MCP](https://stockmarketstack.com/tools/sec-edgar-mcp) puts the same free endpoints behind an
assistant. [SimFin](https://stockmarketstack.com/tools/simfin) and the standardising vendors sell the mapping itself, which is
the expensive part and the part you cannot audit. [Daloopa](https://stockmarketstack.com/tools/daloopa) exists because of what is
never tagged at all — segment splits, operating KPIs and guidance that live in a press release or on
slide 16 — and links each figure back to the page it came from, which is the honest answer to an
untagged number.

A single field is rarely worth an argument. A model built on fifteen of them, sourced from two
vendors, is where this term stops being vocabulary. [Fundamental data and research
platforms](https://stockmarketstack.com/categories/fundamentals-research) is the shelf, and [what is genuinely
free](https://stockmarketstack.com/guides/free-financial-data-sources) is where the free half of it stops.

## Where you will meet this

- [SEC EDGAR](https://stockmarketstack.com/tools/sec-edgar.md)
- [sec-api.io](https://stockmarketstack.com/tools/sec-api-io.md)
- [SEC EDGAR MCP](https://stockmarketstack.com/tools/sec-edgar-mcp.md)
- [Daloopa](https://stockmarketstack.com/tools/daloopa.md)
- [SimFin](https://stockmarketstack.com/tools/simfin.md)
- [Equibles](https://stockmarketstack.com/tools/equibles.md)
- [Financial Datasets](https://stockmarketstack.com/tools/financial-datasets.md)
- [Fintool](https://stockmarketstack.com/tools/fintool.md)
- [Intrinio](https://stockmarketstack.com/tools/intrinio.md)
- [Wisesheets API](https://stockmarketstack.com/tools/wisesheets-api.md)
- [Wisesheets](https://stockmarketstack.com/tools/wisesheets.md)

## FAQ

### If filings are tagged in XBRL, why do two data vendors disagree about a company's revenue?

Because tagging is the issuer's own work and reading it back is the vendor's. The filer chooses which taxonomy element to use, invents an extension element where it thinks none fits, and slices the figure across dimensions. A vendor then decides which of those facts is the headline number, whether an extension maps onto a standard line, and which dimensional slice to keep. Two defensible sets of decisions produce two different numbers from one filing.

### Does XBRL mean I no longer need to parse the document?

Only for the numbers somebody was required to tag. Tagging covers the financial statements, their notes and certain cover-page and specified disclosures; the narrative that explains them is not a set of tagged facts, and material a company publishes in a press release or a slide deck is outside the filing altogether. If what you need is the number behind a KPI nobody had to tag, the document is still the source.

## Sources

1. [Staff Interpretations and FAQs Related to Interactive Data Disclosure](https://www.sec.gov/structureddata/FAQs) — U.S. Securities and Exchange Commission, 2025-11-25
2. [Sample Letter to Companies Regarding Their XBRL Disclosures](https://www.sec.gov/rules-regulations/staff-guidance/disclosure-guidance/sample-letter-companies-regarding-their-xbrl) — U.S. Securities and Exchange Commission, 2023-09-07. Read in September 2026 and still posted as current staff disclosure guidance, marked last reviewed in June 2024.
3. [EDGAR Application Programming Interfaces](https://www.sec.gov/search-filings/edgar-application-programming-interfaces) — U.S. Securities and Exchange Commission, 2025-04-08
4. [Financial Statement Data Sets](https://www.sec.gov/data-research/sec-markets-data/financial-statement-data-sets) — U.S. Securities and Exchange Commission, 2026-06-30
5. [Updated 2025 IFRS taxonomy introduced into the European Single Electronic Format](https://www.esma.europa.eu/press-news/esma-news/updated-2025-ifrs-taxonomy-introduced-european-single-electronic-format) — European Securities and Markets Authority, 2025-09-11

*Last updated 2026-09-21. A reference page, corrected in place — not a dated post.*