What is the DOCX format?

1What is a DOCX file?

DOCX is the format Microsoft Word has used to save documents since Word 2007. It contains the text, the formatting (bold, headings, margins, columns), images, tables, styles, headers and footers, footnotes and review comments. It is the go-to working format: you write, correct and share it so that others can keep editing.

Other word processors also use it, such as LibreOffice, Google Docs and Pages, which open and save it with varying degrees of fidelity. That is why DOCX is the safest format when you want anyone to be able to modify the document.

2How does a DOCX work inside?

If you change a DOCX extension to ZIP and open it, you will see folders and XML files. A main document stores the text and its structure; another defines the styles; others store the relationships to images, numbering, headers or comments. Photos are stored as separate files inside the package.

This design has practical advantages. The file is compressed, so it is usually smaller than the old DOC. Also, if one part gets damaged, the rest can sometimes be recovered. And because the content is structured text, other applications can read or generate it without depending on Word.

• document.xml: the text and paragraph structure.
• styles.xml: the definition of styles and fonts.
• media: the embedded images.

3DOCX, DOC and ODT: what's the difference?

DOC is the binary format from before 2007. It was more opaque, heavier and more prone to corruption. DOCX replaced it as the default format and is based on the open Office Open XML standard, approved by ECMA and ISO. ODT is the equivalent OpenDocument format, used by LibreOffice, which is also open and standardized.

In practice, DOCX and ODT can be swapped, although images, styles or fonts sometimes shift. If you need the result not to vary at all, the safe route is not to change editable formats but to export to PDF.

4DOCX vs. PDF: when to use each one

A DOCX adapts: if a font isn't installed or the program version is different, the text can reflow and the page breaks can change. A PDF doesn't adapt: it keeps the exact appearance. That is why it is recommended to work in DOCX while the document is a draft and send the PDF once it is finished.

If you receive a PDF and need to edit it, you can convert it to DOCX with “PDF to Word.” The result depends on how the PDF was created: if it has real text, it is recovered well; if it is a scan, you need OCR first. For the reverse, “Office to PDF” turns a DOCX into a PDF ready to share.

5Common problems with DOCX files

The most common are formatting that changes when opened on another computer, missing fonts, images that shift, tables that fall out of alignment, and files Word says are damaged. It also happens that a document is very big because it contains high-resolution photos or revision history.

To avoid surprises: embed the fonts or use common ones, avoid placing images with very complex text wrapping, accept or reject tracked changes before sending, and check the document in preview. If the recipient doesn't need to edit, send a PDF.

6Privacy tips when sharing a DOCX

A DOCX stores more than you can see: author name, company, edit dates, comments, tracked changes and sometimes deleted text that is still in the revisions. Before sending it outside your organization, use Word's document inspector or convert it to PDF, which doesn't keep the editing history.

In Rayo PDF GO you can convert Office documents to PDF right on your device, without uploading them to someone else's cloud. Once it is a PDF, you can compress it, password-protect it, sign it or add page numbers with the other tools.

7How to get the most out of DOCX in Rayo PDF GO

The most common workflow is to write in DOCX and deliver in PDF. Convert with “Office to PDF,” check that the page breaks and images are where they should be and, if the file is going to an official submission, compress it with “Compress PDF” to meet the size limit. If you need several documents in one, “Merge PDF” joins them in the order you choose.

In the other direction, if you received a PDF to fill out, “PDF to Word” recovers the text so you can edit it. Always check tables, columns and footers after converting, because that's where differences most often appear. And if the document is a scan, apply “OCR” first so there is text to recover.