.RAR File Format

Introduction

This is the RAR format used from RAR 1.5 until WinRAR 4.x, and still written by later versions when the old format is chosen. Most RAR files from the 1990s and 2000s use it. Its compression changed over the years (RAR 1.5, 2.0 and 2.9 each brought a new method), but the block layout stayed the same. Encrypted archives use AES-128 from RAR 3.0 on. It was replaced by RAR 5.0 in 2013.

Multi-volume archives were first named name.rar, name.r00, name.r01 and so on; RAR 3.0 added the name.part1.rar style.

Structure

The archive is a series of blocks, and even the signature is laid out as one. Every block starts with the same 7-byte header. Numbers are little-endian.

The main block types are 72 for the marker (the signature Rar! 1A 07 00), 73 for the archive header, 74 for a file header, 7A for a subblock such as a comment or recovery record, and 7B for the end of the archive. A file header gives the packed and unpacked sizes, the host operating system, the file’s CRC-32, its DOS date and time, the version needed to extract it, the method (30 for stored up to 35 for best compression), the attributes and the name; the compressed data follows the header. A self-extracting archive has a program in front of the signature.

Variants

• RAR 5.0 archive (RAR5) – WinRAR’s current archive: CRC-32 block headers with variable-length numbers
• RAR 1.5 to 4.x archive (RAR4) – the older RAR format: blocks with a fixed 7-byte header and 16-bit CRC

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