Opening and reading an XBRL file: viewing iXBRL and ESEF reports

A raw XBRL file does not open in Word, Acrobat, and not as a readable document in a regular browser. XBRL is machine data, not a formatted report. iXBRL (Inline XBRL) connects both worlds: it is simultaneously a human-readable (xHTML) report and a tagged data file for systems. Below you will learn how to recognise which file type you have in front of you, which viewer you need, and how to open and check an ESEF or KVK report.

Key facts

• For whom: accountants, controllers and finance professionals who receive an XBRL or iXBRL file and want to see what is inside.

• Core: XBRL is an XML-based standard for structured financial data; iXBRL (Inline XBRL) integrates those tags invisibly into a readable xHTML page.

• Formats: .xbrl or .xml (classic XBRL instance), .xhtml or .html (iXBRL document), .zip and .xbri (report package with multiple files, common for ESEF and for KVK filings in iXBRL).

• Viewer needed: a word processor or PDF reader is not sufficient; use an XBRL processor or iXBRL reader that shows the tags alongside the text.

• Regimes: KVK filings (Dutch Taxonomy via SBR) and ESEF reports (IFRS, listed companies, ESMA/AFM) both use iXBRL, but with different taxonomies and rules.

• Privacy: do not casually upload a report containing confidential figures to just any online tool.

Why an XBRL file is not readable

XBRL (eXtensible Business Reporting Language) is the global open standard for digital business reporting, maintained by XBRL International. An XBRL instance (.xbrl or .xml) contains a series of facts: each fact links a value to a concept from the taxonomy (for example ifrs-full:Revenue, or a concept from the Dutch Taxonomy), a period, a unit and an entity identifier.

If you open such a file in a text editor, you see raw XML: correct for a system, unreadable for us humans. XBRL is designed to make reports machine-readable so that software can find, compare and validate the data.

For a KVK filing via SBR, the XBRL instance was the standard format for years. From financial year 2024 onwards, electronic filers can choose between that XBRL format and the European XHTML/iXBRL format, and from financial year 2025 all legal entities , including the large size class, must file electronically via SBR.

Read more in our article on electronic filing: SBR or iXBRL. Under ESEF, the entire annual financial report is always XHTML; where it contains IFRS consolidated financial statements or the tags do not fit the exact entry points of the taxonomy, iXBRL tags are mandatory and the whole report is bundled into a report package.

The difference between XBRL and iXBRL

iXBRL stands for Inline XBRL. Instead of a separate XML file, iXBRL combines the readable report and the XBRL tags in a single xHTML document. The tags live in special ix: elements (such as ix:nonFraction for numbers and ix:nonNumeric for text) that a browser processes bu. The result: a web page that looks like the annual report to the reader, while software extracts the same structured facts from it as from a classic XBRL instance.

Practical consequence: if you double-click an .xhtml file, a browser opens it as a web page and you see the text. The XBRL tags and taxonomy links remain invisible until you load the file into a viewer that reveals that layer. For more technical background, read our explanation of the difference between XBRL and iXBRL.

Which file type do you have in front of you?

Look at the file extension first. It almost always tells you what you have and how to open it:

Arelle is the best-known open-source XBRL processor and is certified by XBRL International as a validating processor. For standalone XBRL instances it is the reference tool; for iXBRL files you combine Arelle with a viewer plugin or use the Doc2iXBRL iXBRL reader.

A report package has a fixed structure under the Report Package 1.0 specification from XBRL International: a META-INF folder with metadata (reportPackage.json and taxonomyPackage.xml) and a reports folder containing the xHTML file. iXBRL packages have their own extension, .xbri. Both ESEF reports and KVK iXBRL filings use this package structure; SBR Netherlands publishes example annual accounts as .xbri files for each financial year.

Beware: do not manually unzip a report package to open the xHTML file on its own. The viewer needs the full package to correctly resolve the preparer's extension taxonomy; an xHTML file opened on its own shows text, but its tag layer will be incomplete or unusable.

How to open an iXBRL or ESEF report

First determine which file type you have (see the table above). For iXBRL files and report packages you need an iXBRL reader, you can find ours here: https://www.doc2ixbrl.com/ixbrl-reader. With an online viewer you upload the file or the package; with a desktop tool such as Arelle you open it locally. A good viewer shows:

• the visual report, identical to the document it was generated from,

• highlighted amounts and text blocks that carry an XBRL tag,

• per tag: the concept (for example ifrs-full:Revenue or a Dutch Taxonomy concept), the period, the unit, the accuracy and the entity identifier (LEI for ESEF, KVK number for SBR).

What you see in the viewer: an example

Suppose the income statement shows the line "Net revenue 12,345", in thousands of euros. If you click that amount in an iXBRL viewer, you see what the machine reads: the concept (for example ifrs-full:Revenue in an ESEF report, or the revenue concept from the Dutch Taxonomy in a KVK filing), the period (1 January through 31 December of the financial year), the unit (EUR) and the scale. The rendered text "12,345" with a scale factor of one thousand yields the machine value 12,345,000.

This is exactly why a viewer is more than a reading aid: it is a review instrument. The value the reader sees and the value software extracts must mean the same thing. A wrong concept, a wrong period or a wrong scale is invisible to the naked eye in the browser, but immediately visible in the viewer. Anyone who receives an iXBRL file for review therefore walks through the key line items in the viewer: are the concept, period, unit and sign of each tagged amount correct?

Practice on real reports: filings.xbrl.org

If you want to see what tagged annual reports look like in practice, you do not have to wait for your first file to arrive. XBRL International maintains filings.xbrl.org, a public index of tens of thousands of ESEF reports from European listed companies. You can filter by country (for example NL), open a report directly in the built-in Inline XBRL viewer, or download the report package. For the Dutch KVK regime, SBR Netherlands publishes example annual accounts (micro through large) as .xbri packages on sbr-nl.nl for each financial year, including an extension taxonomy, exactly as a real filing looks.

Free viewers and what to look out for

Several online iXBRL viewers are available. Pay attention to three points:

Privacy. Annual accounts contain confidential figures for as long as they are unpublished. Do not upload unfiled or unpublished documents to a tool whose data-processing terms you do not know, and check what the provider says about storage and processing of your files.

Report package support. Not every viewer opens a report package correctly. Check whether the tool supports .zip and .xbri packages and resolves the extension taxonomy internally; a viewer that only handles standalone xHTML files will make you miss part of the tag layer.

Taxonomy version. ESEF uses the ESEF taxonomy, an extension of the IFRS taxonomy that ESMA updates annually. KVK filings use the Dutch Taxonomy (NT), which is likewise renewed per financial year. A viewer that only knows one of the two regimes may display the other incompletely or differently.

Doc2iXBRL offers a free iXBRL Reader. It opens iXBRL files and report packages (.zip, .xbri and .xbr) directly in your browser: the report next to the tagged facts, so that for every figure you can see which XBRL concept, period and unit it is linked to.

Frequently asked questions

How do I open an XBRL file? You open a classic XBRL file (.xbrl or .xml) with an XBRL processor such as the open-source Arelle, or with an online viewer. A text editor shows raw XML, not annual accounts. For iXBRL files and report packages you use an iXBRL reader that renders the report and reveals the tag layer.

What is the difference between XBRL and iXBRL? XBRL is a separate, machine-readable XML file containing structured financial data. iXBRL (Inline XBRL) combines the readable report and the XBRL tags in a single xHTML document, so one file is readable by both humans and systems. ESEF mandates iXBRL for IFRS consolidated financial statements; for KVK filings you can choose between the XBRL instance and iXBRL from financial year 2024 onwards.

What is the full name of iXBRL? Inline eXtensible Business Reporting Language: XBRL tags that are included "inline", meaning within, an xHTML document.

Can I open an iXBRL file in my browser? Yes, a browser displays the text and formatting of the xHTML file. But the XBRL tags remain invisible until you load the file into an iXBRL viewer. Only then can you see which amounts and text blocks are tagged and which taxonomy concept they are linked to.

What is an .xbri file? An .xbri file is an Inline XBRL report package under the Report Package 1.0 specification from XBRL International: a zip container with a fixed structure containing the iXBRL report, the extension taxonomy and META-INF metadata. You open it as a whole in an iXBRL reader; renaming or unzipping it is neither necessary nor wise.

What is an ESEF report package and how do I open it? An ESEF report package is the package in which a listed company submits its annual financial report: the xHTML file with iXBRL tags, the issuer's extension taxonomy and the accompanying metadata, together in one zip container under the Report Packages 1.0 specification. You open it as a whole in an ESEF viewer or iXBRL reader. Read more about the regime in our article on ESEF reporting and iXBRL for IFRS issuers.

Doc2iXBRL for opening and checking iXBRL reports

Doc2iXBRL converts Word and PDF annual accounts into validated iXBRL or SBR files for accountants and internal engagement teams. The built-in iXBRL Reader displays the visual report next to the tagged facts, so you can verify that every figure is correctly tagged for the KVK filing or ESEF submission. Validation runs on the open-source Arelle processor (Calculations 1.1), the SBR Filing Rules and the ESEF rule sets, and flags issues before you file, without guaranteeing KVK or ESMA acceptance.

Sources

• XBRL International – What is XBRL?: introduction to the XBRL standard and the tagging of facts.

• XBRL International – Report Packages 1.0: the specification behind .zip, .xbri and .xbr packages.

• XBRL Certified Software – Arelle: Arelle's certification as a validating processor.

• ESMA – Electronic reporting (ESEF): the ESEF requirements, the ESEF taxonomy and the Reporting Manual.

• KVK – Filing with SBR: digital filing obligation per size class and the Dutch Taxonomy.

• SBR Netherlands – Expansion of electronic filing with the Business Register: XBRL/iXBRL format choice, RTS documentation and example .xbri annual accounts.

• filings.xbrl.org: public index of ESEF reports with a built-in Inline XBRL viewer.