zipalign - Online in the Cloud

PROGRAM:

NAME

zipalign - a ZIP/APK alignment tool for Android application files

SYNOPSIS

To align infile.apk and save it as outfile.apk:

zipalign [ -f ] [ -v ] <alignment> infile.apk outfile.apk

To confirm the alignment of existing.apk:

zipalign -c -v <alignment> existing.apk

The <alignment> is an integer that defines the byte-alignment boundaries. This must always be 4
(which provides 32-bit alignment) or else it effectively does nothing.

DESCRIPTION

zipalign is an archive alignment tool that provides important optimization to Android application
(.apk) files. The purpose is to ensure that all uncompressed data starts with a particular
alignment relative to the start of the file. Specifically, it causes all uncompressed data within
the .apk, such as images or raw files, to be aligned on 4-byte boundaries. This allows all
portions to be accessed directly with mmap() even if they contain binary data with alignment
restrictions. The benefit is a reduction in the amount of RAM consumed when running the
application.

This tool should always be used to align your .apk file before distributing it to end-users. The
Android build tools can handle this for you. When using Eclipse with the ADT plugin, the Export
Wizard will automatically zipalign your .apk after it signs it with your private key. The build
scripts used when compiling your application with Ant will also zipalign your .apk, as long as you
have provided the path to your keystore and the key alias in your project ant.properties file, so
that the build tools can sign the package first.

CAUTION: zipalign must only be performed after the .apk file has been signed with your private
key. If you perform zipalign before signing, then the signing procedure will undo the alignment.
Also, do not make alterations to the aligned package. Alterations to the archive, such as renaming
or deleting entries, will potentially disrupt the alignment of the modified entry and all later
entries. And any files added to an "aligned" archive will not be aligned.

The adjustment is made by altering the size of the "extra" field in the zip Local File Header
sections. Existing data in the "extra" fields may be altered by this process.

For more information about how to use zipalign when building your application, please read Signing
Your Application:

https://developer.android.com/tools/publishing/app-signing.html

OPTIONS

A summary of options is included below.

-f overwrite existing outfile.zip

-v verbose output

-c confirm the alignment of the given file

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