DDOC File

What are DDOC files and how to open them

Are you having problems opening a DDOC file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your DDOC files.

What is a DDOC file?

A .DDOC file is a DigiDoc digital signature file.

The DigiDoc digital signature format is an XML-based container format developed in Estonia for applying legally valid electronic signatures to one or more documents, as part of a public key infrastructure. The SignedDoc container holds the original file(s) plus signature(s), along with validity confirmation data so that later verification of signing time and signer identity is possible. It is mainly used by the state's DigiDoc software and its related libraries.

This format is a first-generation DigiDoc container known as DIGIDOC-XML, often using extension .ddoc. It complies with ETSI standard TS 101 903, using an XAdES profile (roughly XAdES-X-L) to embed certificate validity (via OCSP responses) and other long-term verification data. New files in this format can contain one or more data files inside the container, each described by elements giving filename, MIME type, size and digest, plus signatures that cover all these files. DIGIDOC-XML version 1.3 is the latest version that can still be used to create new .ddoc files; earlier versions (1.0 "SK-XML", 1.1, 1.2) are now supported in reader-only mode.

Technically, files begin with the standard XML declaration (for example <?xml version="1.0" encoding="UTF-8"?>), followed by a root element <SignedDoc format="DIGIDOC-XML" version="1.3">. Within it, elements <DataFile> describe each original file (or references), and <Signature> elements contain an XML Signature (<SignedInfo>, <SignatureValue>, <KeyInfo> etc.), along with validity confirmation data stored via OCSP elements (such as <EncapsulatedOCSPValue>), and certificates in <CertificateValues>. Byte-level signatures include the ASCII-text prefix matching that XML header and the <SignedDoc format ...> opening.

How to open DDOC files

Important: Different programs may use files with the DDOC file extension for different purposes, so unless you are sure which format your DDOC file is, you may need to try a few different programs.

While we have not verified the apps ourselves yet, our users have suggested four different DDOC openers which you will find listed below.

Last updated: October 22, 2026

Various apps that use files with this extension

These apps are known to open certain types of DDOC files. Remember, different programs may use DDOC files for different purposes, so you may need to try out a few of them to be able to open your specific file.

Help us help others

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