ASAR File

What are ASAR files and how to open them

Are you having problems opening an ASAR 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 ASAR files.

What is an ASAR file?

An .ASAR file is an Asar Electron Archive file.

Asar Electron Archive is a proprietary archive format created by the Electron framework to bundle application source files into a single packed file for easier distribution and access. It is used when packaging an Electron app so that its code (JavaScript, HTML, CSS, other static files) is concatenated without compression, yet remains accessible via filesystem-like APIs as if still in separate files.

Electron's tools (for example the @electron/asar module) write these archives at build time by walking the app's directory tree, producing a JSON‐based header describing the files, and then concatenating each file's raw data into one continuous data section. At runtime Electron patches its Node.js filesystem methods so that operations like reading a file or using require work transparently over the archive as if it were a normal directory tree. Files that need direct filesystem access or native binaries may be excluded from the archive and instead kept in an adjacent "unpacked" folder.

The format defines a flat layout: an 8-byte Pickle-serialized header size, followed by a Pickle-serialized JSON string header, followed by the bytes of each file in order. The header entries include metadata such as each file's offset and size (both recorded), possible "executable" flag, optional symlink targets ("link"), and optional integrity information. The integrity object, supported since version 3.1.0 of the asar tool, stores a SHA-256 hash of the entire file, plus per-block hashes to allow runtime verification.

Files in this archive begin with internal signatures including bytes 0x04000000 at offset 0; at offset 15 there is a sequence corresponding to ASCII string ".{\"files\":{"; the header typically contains keywords offset and size.

How to open ASAR files

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

We have not yet verified any programs for Windows that work with this specific file format. If you know one, please use the 'Suggest a program' link below. Thanks!

Last updated: August 20, 2026

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