AAR File

What are AAR files and how to open them

Are you having problems opening an AAR 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 AAR files.

What is an AAR file?

AAR files have multiple uses, and Android Archive is one of them. Read more about the other uses further down the page.

Android Archive

AAR files are the gateway to reusing code and resources across multiple applications. Packaging libraries into a single file format, AARs contain compiled code, resources, and a manifest that outlines dependencies.

By importing an AAR package into an Android Studio project using the “New Module” wizard - with the option of “Import.JAR/.AAR Package” - developers can incorporate it as a dependency just like an Android Library module. Using this method they save time and effort within development by availing reusable components.

AAR files can be created using the Android Gradle Plugin and are typically stored in an Android app project's "libs" directory. They can be imported into an Android Studio project using the "New Module" wizard and selecting the "Import .JAR/.AAR Package" option.

How to open AAR files

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

While we have not verified the app ourselves yet, our users have suggested a single AAR opener which you will find listed below.

Last updated: August 16, 2026

All known file formats using extension .AAR

While Android Archive is a popular type of AAR-file, we know of 3 different uses of the .AAR file extension. Different software may use files with the same extension for different types of data.

Aard Dictionary

Aard Dictionary format files (extension .AAR) are used to deliver full dictionary or encyclopedia datasets for use with the Aard offline dictionary reader. These files store large text or HTML content along with an index so that definitions, articles, or word entries can be searched and retrieved locally on devices without internet access. The Aard application writes .AAR files by compiling source content (for example from MediaWiki dumps or other dictionaries) into a compact, optimized archive that its reader can load. When reading, Aard uses the index inside an .AAR file to find entries matching search terms and renders their stored content for display.

Technical details include a byte signature: the file begins with the ASCII string "aard" starting at byte offset 0 (bytes 0x61 0x61 0x72 0x64) identifying it as an Aard Dictionary file.

Apple Archive

Apple Archives with the .AAR extension are archive files used by Apple's Apple Archive framework. They store one or more files and directories together in a compressed, metadata-rich container. These archives preserve file attributes such as ownership, permissions, file flags, timestamps, extended attributes, and digests. They are useful for packaging up a directory tree into a single file that includes both data and filesystem metadata.

The AppleArchive framework (Swift and C APIs) creates .aar files using tools like the aa command-line utility, or via its programming APIs. Archives can be compressed with different algorithms (including lzfse, zlib, lz4, lzma, raw, and in newer versions LZBITMAP) and support multithreaded processing. Archive contents can later be listed, extracted, verified, or converted using the same framework.

Files always begin with a 4-byte signature "AA01" (legacy files may use "YAA1"). The header size is stored in the next two bytes. After that, field keys represent metadata: TYP (entry type such as regular file, directory, symbolic link, etc.), PAT (path), UID, GID, MOD (permissions), and other fields. For entries containing file data, a DAT field indicates the size of the blob; however the blob content itself comes after the header and is not counted toward the header size.

Various apps that use files with this extension

These apps are known to open certain types of AAR files. Remember, different programs may use AAR 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 AAR file formats, example files, or compatible programs. Please use the links below or email us at submit@file.org to discuss further.