What is an ODT file?

ODT is a container: a wrapper that holds streams encoded by something else. It is used for editing and archiving.

The extension is .odt, and the full name is OpenDocument Text. Both matter less than what the file can hold, which is what the rest of this page is about.

OASIS published it in 2005. The specification is ISO/IEC 26300.

Age is worth knowing here for one practical reason: the older a format is, the more programs have had time to learn it.

It is published in full, so anyone can implement it from the document rather than by inspection, which is why it turns up in so many programs and why files written twenty years ago still open. A published specification is not the same thing as a royalty-free one: where a format wraps a codec, the patent licensing is a separate question the standard does not settle.

ODT is not limited to one page, which matters when converting to something that is: one conversion produces one file holding a single page — the first one, unless the page is something the converter lets you pick.

ODT holds a text document: paragraphs that reflow to fit whatever page they land on.

That is what decides how it converts: the text reflows, so page numbers are a property of the output rather than of the file.

ODT carries optional encryption.

An encrypted file has to be unlocked before anything can convert it, here or anywhere else — a password is not something a converter can work around, and one that claimed to could not be trusted with the file either.

LibreOffice Writer, Microsoft Word and Google Docs read it, and so do most programs of the same kind.

If a file will not open, the format is rarely the problem — it is more often that the program predates it. Converting to something older is the reliable way past that, and it is what the rest of this site is for.

No browser reads it.

That is the single most common reason to convert it: not that the format is bad, but that the place you want to show the file cannot read it.

ODT can hold document properties.

Whether any of it survives a conversion depends entirely on the target, and the honest answer is usually "some of it".

ODT is meant to be opened and changed. Keep the file in this format for as long as the work is going on, and export from it whenever a finished copy is needed.

ODT is the word-processing half of OpenDocument, the format LibreOffice, OpenOffice and Google Docs write when asked for something open. Almost every ODT in circulation was made by one of those, because Microsoft Word will read and write it but never suggests it.

That asymmetry produces the most common arrival here: someone sent an ODT to a Word user, who double-clicked it and got nothing useful — usually because the file association went to a text editor or an archive tool rather than because Word cannot cope. Modern Word opens ODT perfectly well; it simply is not the default owner of the extension.

Rename an ODT to .zip and it opens. Inside are a handful of XML files — the text itself in one, the styles in another, the document metadata in a third — plus a folder holding any images. The structure is straightforward enough to read without tooling.

DOCX is built the same way, which is why converting between them is a genuine structural translation rather than a reconstruction, and why both convert far more faithfully than either does to a binary format like DOC. The two formats disagree on names and details, not on what a document fundamentally is.

OpenDocument is ISO/IEC 26300 and was standardised in 2006 by a committee rather than published by its vendor. That is not a technical advantage in daily use — a paragraph is a paragraph either way — but it is the entire reason the format exists and the reason certain organisations mandate it.

The practical consequence is longevity. A format whose specification is public and whose implementations are open can still be read in thirty years by software nobody has written yet. That argument carries weight for archives, public records and anything with a legal retention period, and very little weight for a letter being sent this afternoon.

Less than people expect. Text, headings, lists, tables, footnotes, endnotes, images, hyperlinks, comments and tracked changes all cross over dependably. For the overwhelming majority of documents the converted file is the same document, and a reader would not be able to tell.

What drifts is at the margins. The two formats express some list numbering, some frame positioning and some field types differently, so a heavily styled document can shift slightly. Line breaking may land in different places if the fonts differ between machines, which moves page breaks in a long document. If exact pagination matters, PDF rather than DOCX is the answer.

Several governments specify ODF for documents they publish or receive, on the reasoning that a citizen should not need to buy particular software to read a public record. The UK adopted it for government documents in 2014; a number of European administrations and municipalities have similar rules, and some are written into procurement requirements.

If you have been asked for an ODT rather than a DOCX, this is almost certainly why, and the request is about the format being open rather than about the software you used. Word will save an ODT — Save As, then choose OpenDocument Text — so meeting the requirement does not mean changing word processor.

An ODT names its fonts and generally does not embed them. A document composed in LibreOffice on Linux may call for fonts that a Windows machine does not have, and the substitute will have different letter widths.

The result is a document that is entirely correct and looks subtly wrong: a heading wrapping to two lines, a table column suddenly cramped, a page ending one line early. Nothing has been lost and nothing needs repairing. Sticking to fonts that exist everywhere avoids it; a PDF removes the question altogether.

ODT can carry macro code, usually LibreOffice Basic. The exposure is smaller than the equivalent in the Microsoft world — largely because attackers target the larger installed base — but it is not zero, and the same caution applies to an unexpected attachment.

LibreOffice disables macros from untrusted sources by default and asks before running anything. Converting the file rather than opening it is a reasonable way to read the contents of something you did not expect, since a conversion takes the text and leaves the code behind.

ODT has a family: ODS for spreadsheets, ODP for presentations, ODG for drawings. They share the same container and the same standard, and they map onto XLSX and PPTX the way ODT maps onto DOCX.

Worth knowing because a folder exported from LibreOffice arrives as a mixture, and the tool that opens one will usually open all of them. If a colleague sends work in ODT, expect the spreadsheets to be ODS rather than XLSX and convert the whole set rather than discovering the second format later.

Keep the ODT if the document will be edited again, especially in LibreOffice — it is the format its own software round-trips without loss, and every conversion is a small translation. Send a DOCX when the recipient is a Word user and the document will be worked on further.

Send a PDF when it is finished. That is the honest resolution of the whole ODT-versus-DOCX question for most documents: the argument only exists while the file is still being edited, and it disappears the moment the document is done.