CAJ File

What are CAJ files and how to open them

Are you having problems opening a CAJ 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 CAJ files.

What is a CAJ file?

CAJ files have multiple uses, and CAJ Database is one of them. Read more about the other uses further down the page.

CAJ Database

These CAJ files contain the full-text and full-image inter-disciplinary Chinese journals from 1915 till today. a CAJ file is a full-text database. The content is split into 5 sections: Literature/history/philosophy, Politics/Military affairs/law, education and social sciences, Electronic Technology and Information Science, Economics and Management.

How to open CAJ files

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

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

Last updated: August 25, 2026

All known file formats using extension .CAJ

While CAJ Database is a popular type of CAJ-file, we know of 2 different uses of the .CAJ file extension. Different software may use files with the same extension for different types of data.

Chinese Academic Journal

Chinese Academic Journal files are a document format developed by China National Knowledge Infrastructure (CNKI) for storing full-text academic journal articles in Chinese. They contain the complete published content of a journal article - including the body text, author details, citations, annotations, and metadata like journal name, publication date, and keywords - preserving the page layout so that the document appears as it did in print. These files are used for accessing scholarly journals within CNKI's "China Academic Journals Full-text" database.

The files are created and distributed by CNKI, often downloaded through their database portal. They are read using CNKI's proprietary viewer software called CAJViewer, which supports viewing, page-by-page navigation, text searching, text recognition (OCR), image extraction, and the ability to export into more commonly used formats like PDF and TXT.

One key technical detail is that these files are in fact PDF documents with added metadata that identify them as CNKI­CAJ files: they begin with the ASCII signature "%PDF-" at offset 0 and include strings like "AUTHOR (CNKI)", "REGISTRY (ADOBE)", "MEDIABOX", "BASEFONT", "FLATEDECODE", among others. This shows they use PDF's internal structures (objects, streams, fonts), which enables tools signed to PDF to recognize their underlying format.

Various apps that use files with this extension

These apps are known to open certain types of CAJ files. Remember, different programs may use CAJ 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

File.org helps thousands of users every day, and we would love to hear from you if you have additional information about CAJ file formats, example files, or compatible programs. Please use the links below or email us at submit@file.org to discuss further.