What Is a UDF File? The UYAP Document Format Explained

What does UDF mean?

UDF is the document format used in UYAP, the National Judiciary Informatics System of Türkiye. Files with the extension .udf are usually called UYAP Document Format. Court decisions, hearing minutes, official letters, notifications and the petitions that lawyers submit are prepared, signed and attached to case files in this format.

UDF files are created with the UYAP Document Editor, which the Ministry of Justice distributes free of charge. It is a Java-based word processor with a Word-like screen: you type and format text, add tables and pictures, and sign the document with an e-signature. The catch is that outside the editor almost no program recognises UDF. Word, Adobe Reader and your phone's file viewer cannot open it.

Do not confuse it with Universal Disk Format

If you search the internet for "UDF" you will meet other meanings. The most common mix-up is with Universal Disk Format, a file system used on CDs, DVDs and Blu-ray discs, which has nothing to do with UYAP. In spreadsheets and databases, UDF also abbreviates "user-defined function". Some general-purpose converter sites confuse the UYAP file with the disc format and give nonsensical results. On this site and in this guide, UDF always means the UYAP document.

Who encounters UDF files?

It is not only lawyers who meet them:

• Courts and enforcement offices produce decisions and letters as UDF files and sign them electronically.
• Lawyers prepare petitions as UDF files and send them through the Attorney Portal; incoming documents are downloaded as UDF too.
• Citizens download decisions and documents from e-Devlet and the UYAP Citizen Portal, and for some procedures (an objection to a traffic fine, for example) must upload a petition as a UDF.
• Expert witnesses and mediators prepare and sign their reports and records as UDF files.
• Clients, companies and people abroad receive UDF files from a Turkish lawyer by WhatsApp or e-mail, and often cannot open them.

What is inside a UDF file?

Technically, a UDF file is a ZIP archive. It always contains a file called content.xml, which holds the whole document. Some documents also contain documentproperties.xml, and e-signed documents have a sign.sgn file. If you rename the extension to .zip, you can see these files; that is also the answer to "why does my UDF file open as a ZIP?".

The content.xml file is a dump of the Java text component that the editor uses. The whole text of the document sits in one block, and a separate section records which character range is bold, which paragraph is centred and which part is a table cell. Paper size, margins, header and footer, page-number format and paragraph styles are in the same file. Images are not stored as separate files but as text-encoded data inside the XML.

One important detail: a UDF has no "pages" stored in it. Pages are calculated when the document is opened, from font metrics and margins. This is why the same document can break onto a different page, by a line or so, in different programs.

UDF compared with PDF

Both look like "documents", but their purposes differ:

• Availability: a PDF opens on every device; a UDF opens only in the UYAP Document Editor or in special tools such as this site.
• Editing: a UDF is an editable text document in the editor; a PDF is a fixed picture of the page, ready for printing.
• Page layout: in a PDF the pages are fixed; in a UDF they are calculated on opening.
• E-signature: in UYAP the signed original is the UDF. A PDF made from a UDF is a copy that does not carry the signature.
• Use: a UDF is for submission to UYAP and the official record; a PDF is more practical for sharing, printing and archiving.

How the e-signature works

Most documents in UYAP are signed with a qualified electronic certificate. The signature lives in the sign.sgn file inside the UDF and covers only content.xml. When it is applied, a digest (a kind of fingerprint) of the content is calculated and added to the signature; if a single character in the content changes, the digest no longer matches. Several people, such as a judge and a clerk, can sign the same file side by side. For this reason, when you edit a signed UDF or convert it to another format, the signature does not move to the new file. A converted PDF or Word file is therefore a copy; for official use, rely on the original signed UDF.

Opening, converting and creating UDF files

To read a UDF without installing a program, use the online UDF viewer. To share or print it, convert it to PDF; to work on it, convert it to Word. In the other direction, you can turn a petition written in Word into a UDF with Word to UDF, or a PDF with PDF to UDF. Before you submit anything to UYAP, open the file in the UYAP Document Editor and sign it. The tools process the file in your browser; see How can you be sure?.

Is a UDF file safe?

A UDF is a data file; it contains no macros or executable code, which makes it less risky than a Word document with macros. Still, be careful with files from people you do not know: fraudsters sometimes try to pass off programs with a double extension, such as "decision.udf.exe", as documents. A real UDF has the extension .udf or, if it came through WhatsApp, .zip. If double-clicking begins to install a program, stop. The viewer on this site reads the content of a document only as text and runs no part of it.

Which programs can open UDF?

Few programs recognise UDF; knowing which one does what saves time:

• UYAP Document Editor (Windows, Mac, Pardus): the official program for reading, editing, signing and submitting to UYAP.
• The official mobile app (Android, iOS): for viewing only.
• Browser-based tools: sites such as udfpdf.com can read UDF and convert it to PDF, Word and other formats; they cannot sign.
• Word, LibreOffice, Adobe Reader and phone file viewers: cannot open UDF directly; you have to convert it first.
• Disc-image and archive programs: disc tools are useless because they take "UDF" to be the disc format; archive programs can only show the XML files inside.