Official Rubyzip repository



Gem Version
Code Climate
Coverage Status

Rubyzip is a ruby library for reading and writing zip files.

Important notes

Updating to version 3.0

The public API of some classes has been modernized to use named parameters for optional arguments. Please check your usage of the following Rubyzip classes:

  • File
  • Entry
  • InputStream
  • OutputStream

Please see Updating to version 3.x in the wiki for details.


Version 3.x requires at least Ruby 3.0.

Version 2.x requires at least Ruby 2.4, and is known to work on Ruby 3.1.

It is not recommended to use any versions of Rubyzip earlier than 2.3 due to security issues.


Rubyzip is available on RubyGems:

gem install rubyzip

Or in your Gemfile:

gem 'rubyzip'


Basic zip archive creation

require 'rubygems'
require 'zip'

folder = "Users/me/Desktop/stuff_to_zip"
input_filenames = ['image.jpg', 'description.txt', 'stats.csv']

zipfile_name = "/Users/me/Desktop/", create: true) do |zipfile|
  input_filenames.each do |filename|
    # Two arguments:
    # - The name of the file as it will appear in the archive
    # - The original file, including the path to find it
    zipfile.add(filename, File.join(folder, filename))
  zipfile.get_output_stream("myFile") { |f| f.write "myFile contains just this" }

Zipping a directory recursively

Copy from here

require 'zip'

# This is a simple example which uses rubyzip to
# recursively generate a zip file from the contents of
# a specified directory. The directory itself is not
# included in the archive, rather just its contents.
# Usage:
#   directory_to_zip = "/tmp/input"
#   output_file = "/tmp/"
#   zf =, output_file)
#   zf.write()
class ZipFileGenerator
  # Initialize with the directory to zip and the location of the output archive.
  def initialize(input_dir, output_file)
    @input_dir = input_dir
    @output_file = output_file

  # Zip the input directory.
  def write
    entries = Dir.entries(@input_dir) - %w[. ..], create: true) do |zipfile|
      write_entries entries, '', zipfile


  # A helper method to make the recursion work.
  def write_entries(entries, path, zipfile)
    entries.each do |e|
      zipfile_path = path == '' ? e : File.join(path, e)
      disk_file_path = File.join(@input_dir, zipfile_path)

      if disk_file_path
        recursively_deflate_directory(disk_file_path, zipfile, zipfile_path)
        put_into_archive(disk_file_path, zipfile, zipfile_path)

  def recursively_deflate_directory(disk_file_path, zipfile, zipfile_path)
    zipfile.mkdir zipfile_path
    subdir = Dir.entries(disk_file_path) - %w[. ..]
    write_entries subdir, zipfile_path, zipfile

  def put_into_archive(disk_file_path, zipfile, zipfile_path)
    zipfile.add(zipfile_path, disk_file_path)

Save zip archive entries sorted by name

To save zip archives with their entries sorted by name (see below), set ::Zip.sort_entries to true


Opening an existing zip file with this option set will not change the order of the entries automatically. Altering the zip file - adding an entry, renaming an entry, adding or changing the archive comment, etc - will cause the ordering to be applied when closing the file.

Default permissions of zip archives

On Posix file systems the default file permissions applied to a new archive
are (0666 - umask), which mimics the behavior of standard tools such as touch.

On Windows the default file permissions are set to 0644 as suggested by the
Ruby File documentation.

When modifying a zip archive the file permissions of the archive are preserved.

Reading a Zip file

MAX_SIZE = 1024**2 # 1MiB (but of course you can increase this)'') do |zip_file|
  # Handle entries one by one
  zip_file.each do |entry|
    puts "Extracting #{}"
    raise 'File too large when extracted' if entry.size > MAX_SIZE

    # Extract to file or directory based on name in the archive

    # Read into memory
    content =

  # Find specific entry
  entry = zip_file.glob('*.csv').first
  raise 'File too large when extracted' if entry.size > MAX_SIZE

Notes on Zip::InputStream

Zip::InputStream can be used for faster reading of zip file content because it does not read the Central directory up front.

There is one exception where it can not work however, and this is if the file does not contain enough information in the local entry headers to extract an entry. This is indicated in an entry by the General Purpose Flag bit 3 being set.

If bit 3 (0x08) of the general-purpose flags field is set, then the CRC-32 and file sizes are not known when the header is written. The fields in the local header are filled with zero, and the CRC-32 and size are appended in a 12-byte structure (optionally preceded by a 4-byte signature) immediately after the compressed data.

If Zip::InputStream finds such an entry in the zip archive it will raise an exception (Zip::StreamingError).

Zip::InputStream is not designed to be used for random access in a zip file. When performing any operations on an entry that you are accessing via Zip::InputStream.get_next_entry then you should complete any such operations before the next call to get_next_entry.

zip_stream =''))

while entry = zip_stream.get_next_entry
  # All required operations on `entry` go here.

Any attempt to move about in a zip file opened with Zip::InputStream could result in the incorrect entry being accessed and/or Zlib buffer errors. If you need random access in a zip file, use Zip::File.

Password Protection (Experimental)

Rubyzip supports reading/writing zip files with traditional zip encryption (a.k.a. “ZipCrypto”). AES encryption is not yet supported. It can be used with buffer streams, e.g.:

Version 2.x

# Writing.
enc ='password')
buffer = Zip::OutputStream.write_buffer(''), enc) do |output|
  output.write my_data

# Reading.
dec ='password'), 0, dec) do |input|
  entry = input.get_next_entry
  puts "Contents of '#{}':"

Version 3.x

# Writing.
enc ='password')
buffer = Zip::OutputStream.write_buffer(encrypter: enc) do |output|
  output.write my_data

# Reading.
dec ='password'), decrypter: dec) do |input|
  entry = input.get_next_entry
  puts "Contents of '#{}':"

This is an experimental feature and the interface for encryption may change in future versions.

Known issues

Modify docx file with rubyzip

Use write_buffer instead open. Thanks to @jondruse

buffer = Zip::OutputStream.write_buffer do |out|
  @zip_file.entries.each do |e|
    unless [DOCUMENT_FILE_PATH, RELS_FILE_PATH].include?(

  out.write xml_doc.to_xml(:indent => 0).gsub("\n","")

  out.write rels.to_xml(:indent => 0).gsub("\n","")
end, "wb") {|f| f.write(buffer.string) }


Existing Files

By default, rubyzip will not overwrite files if they already exist inside of the extracted path. To change this behavior, you may specify a configuration option like so:

Zip.on_exists_proc = true

If you’re using rubyzip with rails, consider placing this snippet of code in an initializer file such as config/initializers/rubyzip.rb

Additionally, if you want to configure rubyzip to overwrite existing files while creating a .zip file, you can do so with the following:

Zip.continue_on_exists_proc = true

Non-ASCII Names

If you want to store non-english names and want to open them on Windows(pre 7) you need to set this option:

Zip.unicode_names = true

Sometimes file names inside zip contain non-ASCII characters. If you can assume which encoding was used for such names and want to be able to find such entries using find_entry then you can force assumed encoding like so:

Zip.force_entry_names_encoding = 'UTF-8'

Allowed encoding names are the same as accepted by String#force_encoding

Date Validation

Some zip files might have an invalid date format, which will raise a warning. You can hide this warning with the following setting:

Zip.warn_invalid_date = false

Size Validation

By default (in rubyzip >= 2.0), rubyzip’s extract method checks that an entry’s reported uncompressed size is not (significantly) smaller than its actual size. This is to help you protect your application against zip bombs. Before extracting an entry, you should check that its size is in the range you expect. For example, if your application supports processing up to 100 files at once, each up to 10MiB, your zip extraction code might look like:

MAX_FILE_SIZE = 10 * 1024**2 # 10MiB
MAX_FILES = 100'') do |zip_file|
  num_files = 0
  zip_file.each do |entry|
    num_files += 1 if entry.file?
    raise 'Too many extracted files' if num_files > MAX_FILES
    raise 'File too large when extracted' if entry.size > MAX_FILE_SIZE

If you need to extract zip files that report incorrect uncompressed sizes and you really trust them not too be too large, you can disable this setting with

Zip.validate_entry_sizes = false

Note that if you use the lower level Zip::InputStream interface, rubyzip does not check the entry sizes. In this case, the caller is responsible for making sure it does not read more data than expected from the input stream.

Compression level

When adding entries to a zip archive you can set the compression level to trade-off compressed size against compression speed. By default this is set to the same as the underlying Zlib library’s default (Zlib::DEFAULT_COMPRESSION), which is somewhere in the middle.

You can configure the default compression level with:

Zip.default_compression = X

Where X is an integer between 0 and 9, inclusive. If this option is set to 0 (Zlib::NO_COMPRESSION) then entries will be stored in the zip archive uncompressed. A value of 1 (Zlib::BEST_SPEED) gives the fastest compression and 9 (Zlib::BEST_COMPRESSION) gives the smallest compressed file size.

This can also be set for each archive as an option to Zip::File:'', create:true, compression_level: 9) do |zip|
  zip.add ...

Zip64 Support

Since version 3.0, Zip64 support is enabled for writing by default. To disable it do this:

Zip.write_zip64_support = false

Prior to version 3.0, Zip64 support is disabled for writing by default.

NOTE: If Zip64 write support is enabled then any extractor subsequently used may also require Zip64 support to read from the resultant archive.

Block Form

You can set multiple settings at the same time by using a block:

  Zip.setup do |c|
    c.on_exists_proc = true
    c.continue_on_exists_proc = true
    c.unicode_names = true
    c.default_compression = Zlib::BEST_COMPRESSION


Rubyzip is known to run on a number of platforms and under a number of different Ruby versions.

Version 2.3.x

Rubyzip 2.3 is known to work on MRI 2.4 to 3.1 on Linux and Mac, and JRuby and Truffleruby on Linux. There are known issues with Windows which have been fixed on the development branch. Please let us know if you know Rubyzip 2.3 works on a platform/Ruby combination not listed here, or raise an issue if you see a failure where we think it should work.

Next (version 3.0.0)

Please see the table below for what we think the current situation is. Note: an empty cell means “unknown”, not “does not work”.

OS/Ruby 2.5 2.6 2.7 3.0 3.1 3.2 3.3 Head JRuby JRuby Head Truffleruby 23.1.2 Truffleruby Head
Ubuntu 22.04 CI CI CI CI CI CI CI ci CI ci CI ci
Mac OS 12.7.3 CI x x ci ci ci ci ci x x
Windows 10 x
Windows Server 2022 CI CI mswin
CI ucrt

Key: CI - tested in CI, should work; ci - tested in CI, might fail; x - known working; o - known failing.

Ruby 3.0+ are also tested separately with YJIT turned on.

See the Actions tab in GitHub for full details.

Please raise a PR if you know Rubyzip works on a platform/Ruby combination not listed here, or raise an issue if you see a failure where we think it should work.


Install the dependencies:

bundle install

Run the tests with rake:


Please also run rubocop over your changes.

Our CI runs on GitHub Actions. Please note that rubocop is run as part of the CI configuration and will fail a build if errors are found.

Website and Project Home


See for a comprehensive list.

Current maintainers

  • Robert Haines (@hainesr)
  • John Lees-Miller (@jdleesmiller)
  • Oleksandr Simonov (@simonoff)

Original author

  • Thomas Sondergaard


Rubyzip is distributed under the same license as Ruby. In practice this means you can use it under the terms of the Ruby License or the 2-Clause BSD License. See and for details.

Research notice

Please note that this repository is participating in a study into sustainability
of open source projects. Data will be gathered about this repository for
approximately the next 12 months, starting from June 2021.

Data collected will include number of contributors, number of PRs, time taken to
close/merge these PRs, and issues closed.

For more information, please visit
our informational page or download our participant information sheet.