# Tar / Zip / 7z Parser

> List entries, sizes and headers inside archive files without extracting them.

- Page: https://decoder.tools/archive-parser
- Category: File Format & Archives
- Status: live, runs in the browser
- Last reviewed: 2026-10-23

An archive parser reads the index structures of a zip, tar or 7z file — the central directory, the tar header blocks — to list every entry's name, size, timestamp and compression method without extracting anything to disk.

## What is the Tar / Zip / 7z Parser?

The three formats work quite differently. A zip archive has a central directory at the end of the file listing every entry with its offset, sizes and CRC, which is why zip supports random access and why a zip can be read even when appended to another file. Tar is a stream of 512-byte header blocks, each followed by the file data, with no index — you must read it end to end. 7z uses its own container with a compressed header and typically LZMA2 inside.

Reading the index without extracting is the safe way to inspect an untrusted archive. Zip-slip — entries whose names contain ../ to escape the extraction directory — remains a live vulnerability class, and zip bombs advertise modest compressed sizes while expanding to terabytes. Both are visible in the listing before you extract.

The listing also answers everyday questions: whether an archive has a single top-level directory or will scatter files across your working directory, and which compression method was used.

## How to use the Tar / Zip / 7z Parser

1. Load the archive — it is parsed locally and never uploaded.
2. Review the entry list: names, compressed and uncompressed sizes, timestamps.
3. Check for ../ in paths and compare compressed to uncompressed ratios before extracting.

## When to use it

- Inspecting an untrusted archive for path-traversal entries before extraction.
- Checking what a download actually contains without unpacking it.
- Spotting a zip bomb by its compression ratio.

## Tar / Zip / 7z Parser at a glance

| | |
|---|---|
| Zip | Central directory at end of file · magic 50 4B |
| Tar | 512-byte header blocks, no index · usually .tar.gz |
| 7z | Own container, LZMA2 by default · magic 37 7A BC AF |
| Safety check | Look for ../ in entry names (zip-slip) |

## FAQ

### What is zip-slip?

A vulnerability where an archive entry's name contains ../ sequences so extraction writes outside the intended directory, potentially overwriting system files. Reviewing entry names before extracting is the reliable defence.

### Why does tar need gzip?

Tar only concatenates files with headers; it has no compression of its own. That is why archives are almost always .tar.gz or .tar.xz — tar for the bundling, another algorithm for the compression.

### Can I tell if an archive is encrypted?

Yes. Zip sets an encryption flag in each entry's header, so the listing shows which entries are protected — though filenames remain readable unless the archive uses header encryption.