File Content Extraction 25.4
Filter SDK C++ Programming Guide

# Obtain Format Information

The file format detection module (`kwad`) detects a file's format, and reports the information to your application.

When detecting the file format, File Content Extraction uses the content of the file rather than the file extension. In some cases, the file extension can be an unreliable marker because it might refer to many different versions of an application, or files from different pieces of software. In other cases, a file might be incorrectly labeled by accident or by a malicious actor.

File Content Extraction ignores the file extension and examines the content of a file to identify it correctly. Many formats use a ‘magic number’ at the start, which are useful for identification. However, magic numbers can be ambiguous and are sometimes insufficient, so File Content Extraction examines the file more deeply to ensure the basic validity of a file before it determines the format and increase the confidence in the result.

In all cases, File Content Extraction does the minimum amount of work required to be confident of the file format, so it can detect formats as quickly as possible.

You can detect the format of a file by using the info method on a document object. For example:

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    auto myinput = keyview::io::InputFile{ std::string("InputFile.docx") };
    auto doc = session.open(myinput);

    std::cout << "Format:\t" << static_cast<int>(doc.info().format()) << "\n";
    std::cout << "Description:\t" << doc.info().description() << "\n";
    std::cout << "Version:\t" << doc.info().version() << "\n";
    std::cout << "Category:\t" << static_cast<int>(doc.info().category()) << "\n";
    std::cout << "Category Name:\t" << doc.info().category_name() << "\n";
    std::cout << "Encrypted:\t" << std::boolalpha << doc.info().encrypted() << "\n";

For information about mapping detected formats to document readers, see File Formats and Document Readers.

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Version 25.4 | Last updated October 2025

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Product: File Content Extraction 25.4

Topic Title: Obtain Format Information