Opening a ZFO File

The ZFO file type is primarily associated with Datová schránka.

ZFO	File extension: ZFO
	File type:	document container

What is a ZFO file?

ZFO files mostly belong to Datová schránka. ZFO files are used in specialized Czech systems for handling official documents.
These files come in two main variants:

• Certificate2 Format: This version serves as a data box file used for secure government communications. It is part of the Czech eGovernment system managed by services such as Datová schránka and sometimes associated with ISDS eDesky. This file embeds digital certificate details for authentication.
• ZIP Format: In this form, the file acts as a form archive containing a zipped XSL-FO form document. XSL-FO (Extensible Stylesheet Language Formatting Objects) is used to format XML-based documents. Companies like Form Filler and Formular 602 use this archive format for processing official form documents.

To view or open a ZFO file, first determine its internal structure.

• If it behaves like a ZIP archive, try a standard extraction tool (e.g., 7-Zip or WinZip) to access the XSL-FO documents.
• If it does not open in a ZIP utility, it is likely a certificate2-based file that needs dedicated eGovernment software such as Datová schránka.

Additional information: Few know that the same extension can hide two very different internal formats and a simple file name does not reveal whether it contains digital certificates or a compressed form archive.

How do you open ZFO files?

You need a suitable software like Datová schránka to open a ZFO file. Without proper software you will receive a Windows message "How do you want to open this file?" or "Windows cannot open this file" or a similar Mac/iPhone/Android alert. If you cannot open your ZFO file correctly, try to right-click or long-press the file. Then click "Open with" and choose an application. You can also display a ZFO file directly in the browser:. Just drag the file onto this browser window and drop it.

Online ZFO Text Viewer

Choose your .zfo file to analyze

or drag and drop it here

Online File Viewer

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ZFO file format:

The file format, which is the arrangement and type of data in a file, determines which program can open the file. The file format can be deduced from the file extension and the signature. However, different programs can use the same file extension, and file extensions can be assigned incorrectly. Exact knowledge of the format is therefore important in order to solve problems occurring in files. Our evaluation of the ZFO files is as follows:

Files with the ZFO extension are quite widely used. This file type mainly uses a defined ZFO format. The file formats most commonly found in ZFO files are:

• 65% of all ZFO files save the data in certificate file format. A digital certificate is a unique, digitally signed document which authoritatively identifies the identity of an individual or organization. Using public key cryptography, its authenticity can be verified to ensure that the software or website you are using is legitimate. The content consists of readable text data, which can be read using a text editor. The average file size is 240 KB with most files being between 12 KB and 2 MB in size. It is a modern file type. The following keywords are characteristic: <q:MessageDownloadResponse xmlns:q="http://isds.czechpoint.cz/v20/message" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" isds_send="ht. Such ZFO files store data about zprava, prijata, odeslana, priloha, dorucenka, enka, doru, datova and datov.
• 30% of all ZFO files internally use the ZIP format, multiple files are compressed and combined into one ZFO file. 1 to 4 compressed files are common. Common included file names are form.fo, \summary\summary.xml, \thumbnails\fplarge.jpg and \thumbnails\fpsmall.jpg. If you'd like to see the images and files included, just rename the file extension to .zip and double-click. The files are 32 KB to 540 KB in size, with a median of 83 KB. Certain words are almost always found in the files, such as form.fo. The following filename is common: zadost_zrizeni_ds.zfo. Files like these are about zadost, vyplneno, zrizeni, formular, vklad, kultura and navrh.

All other ZFO files (5%) have no consistent format. They are often associated with nemovitosti, katastru, prava, sport, dotaznik, jednolety or prukaz. If you want to find out which format your ZFO file belongs to, just click on the button "Choose your .zfo file to analyze".