XBRL (eXtensible Business Reporting Language) is an open, XML-based standard for tagging financial data so that software can read and process it. Instead of reporting "Net income: $96,995 million" only as text on a page, XBRL attaches a machine-readable tag identifying what the value represents, the period it covers, the entity, the currency, and the precision.
The SEC requires public companies to submit the financial statements in their 10-K and 10-Q filings in XBRL format, which is what makes large-scale fundamental analysis from SEC filings possible.
Full guide: What Is XBRL? How SEC Tagging Affects Your Investment Data (2026)