zipalign Man page

ZIPALIGN(1) General Commands Manual ZIPALIGN(1)


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


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

zipalign [ -f ] [ -v ] infile.apk outfile.apk

To confirm the alignment of existing.apk:

zipalign -c -v existing.apk

The is an integer that defines the byte-alignment boundaries. This
must always be 4 (which provides 32-bit alignment) or else it effectively does


zipalign is an archive alignment tool that provides important optimization to
Android application (.apk) files. The purpose is to ensure that all uncom‐
pressed 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 por‐
tions 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 con‐
sumed 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 com‐
piling 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 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:


A summary of options is included below.

-f overwrite existing

-v verbose output

-c confirm the alignment of the given file


zipalign was written by the Android Open Source Project.

July 2014 ZIPALIGN(1)