What is iXBRL? (And How to View an iXBRL File Online)

If you’ve ever filed or received company accounts in the UK, you’ve likely come across the term iXBRL. But what is iXBRL exactly, and how do you actually open and view an iXBRL file once you have it? Whether you’re an accountant, a company director, or a researcher, knowing how to view iXBRL file online is an increasingly essential skill — and you don’t need expensive software to do it.

In this guide, we’ll demystify the format, walk you through who needs to read these files, and show you exactly how to open an ixbrl file using a free iXBRL viewer that runs directly in your browser.

What is iXBRL?

iXBRL stands for Inline eXtensible Business Reporting Language. It’s the standard format mandated by Companies House and HMRC for filing company accounts and tax computations in the UK. Put simply, iXBRL is a clever hybrid: it wraps a human-readable HTML document (the accounts pages you actually read) with invisible, machine-readable XBRL tags embedded directly into the same file.

This dual nature is what makes iXBRL so powerful. A director or accountant can open the file and see a normal-looking set of accounts — balance sheet, profit and loss, notes — while simultaneously, Companies House and HMRC software can parse the embedded XBRL tags to extract every figure automatically, no manual data entry required. For UK micro-entities filing under FRS 105, iXBRL is the format you submit every year. And if you ever need to check what was filed, you’ll need a free iXBRL viewer to inspect it properly.

Why you might need to view an iXBRL file

Accountants checking a client's filed accounts

Accountants and bookkeepers are the most frequent users of xbrl viewer online tools. Before submitting final accounts to Companies House, a responsible accountant will always view ixbrl file online to verify that every number in every tag is correct. A quick spot-check in a viewer can catch a transposed digit or a mis-tagged liability before it becomes a rejected filing.

Directors reviewing their own filing

Company directors have a legal duty to approve their accounts before filing. Even if your accountant prepared the iXBRL, you should still open and view the iXBRL file yourself to confirm it reflects the numbers you signed off. An online iXBRL viewer makes this easy — you don’t need to install anything or request special access.

Researchers and investors analysing public data

Companies House filings are public records. Researchers, analysts, and investors routinely download iXBRL files from the public register to benchmark performance, spot trends, or conduct due diligence. A good viewer lets you toggle between the formatted document view and a structured facts table, and even export the tagged figures — which is far more efficient than copying numbers out of a PDF.

How to view an iXBRL file online (step by step)

The easiest way to open an iXBRL file is with a browser-based viewer. Follow these five simple steps, and you’ll be reading your file in under a minute:

1. Locate your iXBRL file. iXBRL files typically have the extension .html, .xhtml, or occasionally .xml. If you downloaded it from Companies House or received it from your accountant, it’s almost certainly one of these three.
2. Open the QuickXBRL free iXBRL viewer. Navigate to the xbrl viewer online in any modern browser — Chrome, Firefox, Safari, or Edge all work perfectly. No account creation is required.
3. Drag & drop or click to upload. Drop your iXBRL file onto the upload area, or click the upload button to select it from your device. Everything happens locally in your browser, so your file never leaves your machine.
4. Browse document view or switch to facts table. The default view shows the formatted, human-readable accounts exactly as they were filed. Switch tabs to the Facts Table for a structured list of every XBRL-tagged value — including the concept name, period, and monetary amount.
5. Export facts to CSV if needed. If you want to work with the data in Excel or another spreadsheet tool, simply click Export to CSV and download the full facts table as a comma-separated file.

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How our iXBRL viewer compares to the FRC viewer and other tools

Companies House and the FRC (Financial Reporting Council) both provide their own free viewers for iXBRL and XBRL documents, and those are perfectly valid options. QuickXBRL’s viewer takes a different, privacy-first approach: it runs entirely client-side in your browser, meaning your file never leaves your browser — nothing is sent to, or stored on, any server. That’s a meaningful distinction for accountants handling sensitive client data or directors looking at draft filings.

We’ve also designed a clean, modern interface optimised specifically for UK micro-entity and small company accounts. Rather than burying core information behind multiple menus, our viewer extracts the key metadata at-a-glance — company name, company number, reporting period, and accounts type (FRS 105 micro, FRS 102 small, etc.) — as soon as the file loads. Combined with one-click CSV export, it’s the fastest way to answer the questions you actually have when you open an ixbrl file.

Frequently asked questions