11 August 2026

IDML file, INDD, XLIFF: which file actually counts in translation

Your translation vendor asks for an IDML file because translation tools cannot read the binary INDD format. IDML is XML based and exposes text along with its formatting as markup. That is the moment the text leaves the layout, and that is where the work nobody invoices begins.

1What is an IDML file?

An IDML file is Adobe InDesign’s XML-based exchange format. It carries the same text and the same formatting as the original, but in a structure other programs can read.

Translation tools need this format because the binary InDesign document is unreadable to them. You create it in InDesign under File > Export and choose InDesign Markup (IDML). The format has been available since InDesign CS4.

Technically an IDML file is a ZIP archive of several XML documents describing paragraph styles, character styles, text frames and how those frames are linked. What matters more is what it does not contain:

• No images. Linked graphics stay outside as separate files; the IDML only points at them.
• No fonts. Anyone without your corporate typeface sees a different document.
• No text inside graphics. Labels within placed images are not InDesign text and never appear in the export.

Hand over the IDML alone and you hand over a document that looks different at the other end.

The export takes seconds. The work starts afterwards.

2IDML or INDD: what is the difference?

INDD is the original document, IDML a derivative of it. The original is binary and complete, the derivative is readable and incomplete.

In practice the text goes out and comes back, but not as the same document. You export INDD to IDML, the vendor translates, the IDML comes back, and you open it in InDesign again.

What you get is a new document, not your old one. Every setting that lived in the original and has no equivalent in the IDML has to be checked afterwards. The return trip works, but it is a rebuild, not an update of the original.

3Can you open an INDD file without InDesign?

Not with standard tools. INDD is a closed binary format and Adobe does not publish an open library for it. Server-side processing requires Adobe InDesign Server.

InDesign Server is the server edition of InDesign. It has no user interface and is driven through the scripting API that Adobe documents for developers. It can open, modify and output documents automatically.

Procurement is the catch. Three things make this route unattractive for the companies producing the documents:

• No subscription. InDesign Server is not sold like Creative Cloud; it is licensed through Adobe partners.
• Order of magnitude. The licence sits in a range that is hard to justify for a single company with a handful of publications.
• Ongoing effort. Then there is running it, maintaining it and writing the scripts it needs before it does anything at all.

The question is not whether you buy InDesign Server. The question is whether your tool already runs one.

4Why translate the package directly?

Sending the InDesign package instead of an IDML removes the rebuild and keeps everyone on the file that actually goes to print.

A package holds the INDD document, the linked images and the fonts in use, all in one folder. InDesign creates it under File > Package. Four things change as a result.

The drawback is just as clear: not every tool can do this. Most translation tools insist on IDML because they cannot read INDD and do not run an InDesign Server. So there is one specific question to ask a vendor: Do you accept the complete package, or do you need an IDML?

The centre shows the native InDesign layout. You click the text and edit it right there. On the right sit similar entries from the translation memory, so translation and review stay consistent.

5Where does XLIFF come in?

XLIFF is the format translation tools work in internally. You will rarely see it.

The tool breaks your IDML into segments, stores them as XLIFF, has them translated and rebuilds an IDML from the result. XLIFF stands for XML Localization Interchange File Format and is an OASIS standard.

Its purpose is independence from the source format. Whether the text came from InDesign, from Word or from a software user interface, in XLIFF it all looks the same. That is exactly what makes it useful and, at the same time, blind to the layout.

XLIFF becomes relevant to you in two situations:

• When changing vendors. XLIFF is one of the formats a project in progress can be handed over in.
• When tracing an error. If formatting is missing on return, the question is whether it was already lost during segmentation.

6TMX is not an output, it is an asset

TMX is the exchange format for translation memories, meaning your collection of already translated and approved sentences. It is the only file here that belongs to your company rather than to a document.

A translated catalogue is a finished product. A maintained translation memory is an asset that makes every later project cheaper.

The distinction matters commercially because approved passages do not have to be translated or reviewed again. Which leads to a question that is missing from most tenders:

Who owns the translation memory, and in what format do you get it out? If a vendor holds the asset and will not export it as TMX, switching is expensive no matter how good the rates look.

7The real cost driver: the file travels

The format does not cost money. The number of handovers does. Every conversion is a place where something can be lost and where someone has to check whether it was.

With two languages this is manageable. With fourteen languages and an annual update it becomes the larger part of the project effort, and it is the part that lands internally and therefore never appears in a quote comparison.

8How InTO handles this

InTO is our platform for translating documents inside the layout. InDesign files are uploaded as INDD, as IDML or as a complete package, and they stay there.

For the format question this means three things. The route through an IDML is possible but not required. The package can be processed directly, so images and fonts are visible on screen. And review happens on the rendered page, not on a PDF printout next to it.

Word, PowerPoint and Excel are supported alongside InDesign. At Hörmann KG, our reference customer, the result looked like this:

These figures come from a layout-heavy InDesign portfolio with DTP previously outsourced in full. A different starting point produces different numbers. The details are in the Hörmann case study, with further examples in our References.