ZIP Detection and Salvaging

Table of Contents

ZIP Salvaging
Other Detection Hints
Related Topics

Apache Tika uses the DefaultZipContainerDetector to detect ZIP-based file formats including plain ZIP archives, OOXML documents (docx, xlsx, pptx), ODF documents (odt, ods, odp), EPUB, JAR files, and many others.

ZIP Salvaging

When a ZIP file is truncated or corrupted in a way that prevents it from being opened normally, Tika can attempt to "salvage" the file by:

Streaming through the local file headers (at the beginning of the ZIP)
Reconstructing a valid ZIP structure with a proper central directory

This allows Tika to extract content from partially downloaded files, truncated archives, or files with damaged central directories.

When Salvaging Occurs

Salvaging only happens when:

The DefaultZipContainerDetector (or a detector that includes it) is used
The detector is called with ParsingIntent.WILL_PARSE in the ParseContext (set automatically by AutoDetectParser)
The ZIP file cannot be opened directly via ZipFile

Detecting Salvaged Files

When a file is salvaged, Tika sets the following metadata property:

zip:salvaged = true

You can check for this in your code:

import org.apache.tika.metadata.Zip;

boolean wasSalvaged = metadata.getBoolean(Zip.SALVAGED);

Direct Parser Usage

If you call parsers directly without going through AutoDetectParser, or if you use a custom detector that doesn’t include DefaultZipContainerDetector, the salvaging behavior will not apply. In these cases:

Truncated or corrupted ZIP files may fail to parse
You may get different results compared to using AutoDetectParser
The parser will attempt to open the file directly, which may fail

For consistent behavior with truncated files, use AutoDetectParser:

// Recommended: Uses detection with salvaging
AutoDetectParser parser = new AutoDetectParser();
parser.parse(inputStream, handler, metadata, context);

Rather than calling parsers directly:

// Direct parser: No salvaging support
ZipParser parser = new ZipParser();
parser.parse(inputStream, handler, metadata, context);  // May fail on truncated files

Other Detection Hints

The detector also sets additional metadata hints for parsers:

zip:detectorZipFileOpened: true if the detector successfully opened the ZIP as a ZipFile. The ZipFile object is available via TikaInputStream.getOpenContainer() for reuse by parsers.
zip:detectorDataDescriptorRequired: true if streaming detection required DATA_DESCRIPTOR support. This hint helps parsers choose the correct streaming mode.