What is the XBRL file format?
XBRL - eXtensible Business Reporting Language - is a text file format based on XML, created as a markup language for sharing and exchanging business data. .xbrl files store financial information or reports in a machine-readable, structured form that software can validate, compare and analyse automatically. XBRL is a universal and portable standard not tied to any software platform, and is an open standard distributed under a free licence by XBRL International.
Data in .xbrl files is organised using a well-defined structure. Each file starts with a root <xbrl> element (or <xbrli:xbrl> with the namespace declared) that references one or more taxonomy schemas (.xsd files) defining the meaning of every tag. The content following the root element constitutes so-called Business Facts, which can be divided into the following groups:
- items - elements holding a single value,
- tuples - elements with multiple values; can be nested.
Every fact is accompanied by a context element that identifies the reporting entity, the time period covered and the unit of measurement, making each data point self-describing. Files that combine .xbrl tags embedded inside a human-readable XHTML document are called Inline XBRL (.ixbrl), allowing the same filing to be viewed in a web browser and processed by software simultaneously.
XBRL 1.0 was introduced in 2000; XBRL 2.1, the stable and current specification, was recommended by XBRL International in 2003 and has remained the core standard since. Documents in the XBRL standard are required by financial regulators in the United States (SEC EDGAR) and the U.K.; in Poland, since 2020 companies listed on the stock exchange are required to provide reports adhering to the ESEF standard using .xbrl files. Regulatory packages are often distributed as ZIP archives bundling the instance document together with the required taxonomy schemas and linkbases. There are dedicated tools and plug-ins for popular applications that allow creating and validating reports in XBRL format.
Security & safety
RISK: LOWAn XBRL file is plain XML data with no executable code, so opening it is low risk. Standard XML caution applies: a malicious file could in theory reference external entities (XXE), so use a proper XBRL tool (Arelle) or a text editor rather than feeding unknown files to a permissive XML parser. The data itself is public regulatory filing information. Avoid dubious "XBRL viewer" download sites; Arelle (open-source) and official regulator viewers are the trustworthy options.
Format details
in a nutshellPrograms that open XBRL files
Windows3 apps
Notepad
Open-source Open to read the raw XML tags (with the XML Tools plugin for formatting). Inspection only - not a rendered report. 
Arelle
Open-source Open the .xbrl in Arelle to view facts as tables, validate against the taxonomy, and export to CSV/JSON. The standard free XBRL tool.
Microsoft Excel (Power Query / XBRL add-ins)
Paid Import the XML or use an XBRL add-in to pull tagged facts into a worksheet for analysis. 
macOS2 apps
TextEdit
Built-in Open the raw XML to inspect tags (use 'Make Plain Text'). Inspection only; use Arelle for a real report view. 
Linux1 app
Arelle
Open-source Run Arelle (GUI or command line) to validate and export XBRL; the cross-platform standard.
SEC EDGAR Financial Report viewer
Free For SEC filings, view the company's XBRL data rendered as financial statements in the browser. Technical details
deep spec| File encoding | UTF-8 plain text; the file is a well-formed XML document |
| MIME type | application/xbrl+xml (also accepted: application/xml, text/xml) |
| File signature | Opens with the standard XML declaration `<?xml ...?>` at byte offset 0; further identified by a root `<xbrl>` or `<xbrli:xbrl>` element and the XBRL 2003 instance namespace URI |
| Core namespace | http://www.xbrl.org/2003/instance (prefix xbrli); each filing imports additional taxonomy-specific namespaces such as US-GAAP, IFRS or ESEF |
| Business fact types | Items (single value per concept) and Tuples (multi-value, nestable containers); both types carry mandatory context and unit references |
| Context model | Every reported fact references a <context> element specifying the reporting entity identifier, the period (instant or start/end duration) and the unit of measurement |
| Taxonomy linkage | A <schemaRef> link element points to external .xsd taxonomy schemas and linkbase files that define the full set of allowed reporting concepts |
| Validation layers | XML Schema (XSD) validity, then XBRL 2.1 instance rules, then calculation linkbase arithmetic checks, and finally taxonomy-specific formula rules |
| Inline XBRL variant | Inline XBRL (.ixbrl) embeds the same tagged facts inside an XHTML document, making the filing both browser-readable and machine-processable from a single file |
| Filing packaging | No native compression; regulatory submissions are wrapped in a ZIP taxonomy package bundling the instance document, taxonomy schemas and linkbases |
| Typical file size | Tens of KB to a few MB; annual reports for large companies can contain thousands of individually tagged facts |
| Platform support | Cross-platform; any XML-capable parser can read the file; specialist tools include Arelle (Python-based), Fujitsu XWand and the SEC EDGAR inline viewer |
| Regulatory mandates | Required for SEC EDGAR filings (USA), Companies House and FCA returns (UK), ESEF for EU-listed companies, and securities regulators in Japan, Australia, India and others |
| Namespace prefix convention | xbrli for core instance elements; dei (Document and Entity Information) for common header facts in US SEC filings; taxonomy-specific prefixes per filing |
| Released | 2000 (XBRL 1.0); XBRL 2.1 specification recommended 2003 |
| Latest version | XBRL 2.1 (with the Open Information Model / xBRL-XML and successors); Inline XBRL (iXBRL) for human-readable filings |
| Open standard | Yes · royalty-free |
| Specification | www.xbrl.org |
XBRL conversions
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