8 <h2>In this document</h2>
11 <li><a href="#enabling">Enabling ProGuard</a></li>
13 <li><a href="#configuring">Configuring ProGuard</a></li>
16 <a href="#decoding">Decoding Obfuscated Stack Traces</a>
19 <li><a href="#considerations">Debugging considerations for published
29 <a href="http://stuff.mit.edu/afs/sipb/project/android/sdk/android-sdk-linux/tools/proguard/docs/index.html#manual/introduction.html">ProGuard
33 <a href="http://stuff.mit.edu/afs/sipb/project/android/sdk/android-sdk-linux/tools/proguard/docs/index.html#manual/retrace/introduction.html">ProGuard
34 ReTrace Manual »</a>
40 <p>The ProGuard tool shrinks, optimizes, and obfuscates your code by removing unused code and
41 renaming classes, fields, and methods with semantically obscure names. The result is a smaller
42 sized <code>.apk</code> file that is more difficult to reverse engineer. Because ProGuard makes your
43 application harder to reverse engineer, it is important that you use it
44 when your application utilizes features that are sensitive to security like when you are
45 <a href="{@docRoot}google/play/licensing/index.html">Licensing Your Applications</a>.</p>
47 <p>ProGuard is integrated into the Android build system, so you do not have to invoke it
48 manually. ProGuard runs only when you build your application in release mode, so you do not
49 have to deal with obfuscated code when you build your application in debug mode.
50 Having ProGuard run is completely optional, but highly recommended.</p>
52 <p>This document describes how to enable and configure ProGuard as well as use the
53 <code>retrace</code> tool to decode obfuscated stack traces.</p>
55 <h2 id="enabling">Enabling ProGuard</h2>
57 <p>When you create an Android project, a <code>proguard.cfg</code> file is automatically
58 generated in the root directory of the project. This file defines how ProGuard optimizes and
59 obfuscates your code, so it is very important that you understand how to customize it for your
60 needs. The default configuration file only covers general cases, so you most likely have to edit
61 it for your own needs. See the following section about <a href="#configuring">Configuring ProGuard</a> for information on
62 customizing the ProGuard configuration file.</p>
64 <p>To enable ProGuard so that it runs as part of an Ant or Eclipse build, set the
65 <code>proguard.config</code> property in the <code><project_root>/project.properties</code>
66 file. The path can be an absolute path or a path relative to the project's root.</p>
68 <p class="note"><strong>Note:</strong> When using Android Studio, you must add Proguard
69 to your <code>gradle.build</code> file's build types. For more information, see the
70 <a href="http://tools.android.com/tech-docs/new-build-system/user-guide#TOC-Running-ProGuard"
71 >Gradle Plugin User Guide</a>.
73 <p>If you left the <code>proguard.cfg</code> file in its default location (the project's root directory),
74 you can specify its location like this:</p>
75 <pre class="no-pretty-print">
76 proguard.config=proguard.cfg
79 You can also move the the file to anywhere you want, and specify the absolute path to it:
81 <pre class="no-pretty-print">
82 proguard.config=/path/to/proguard.cfg
86 <p>When you build your application in release mode, either by running <code>ant release</code> or
87 by using the <em>Export Wizard</em> in Eclipse, the build system automatically checks to see if
88 the <code>proguard.config</code> property is set. If it is, ProGuard automatically processes
89 the application's bytecode before packaging everything into an <code>.apk</code> file. Building in debug mode
90 does not invoke ProGuard, because it makes debugging more cumbersome.</p>
92 <p>ProGuard outputs the following files after it runs:</p>
95 <dt><code>dump.txt</code></dt>
96 <dd>Describes the internal structure of all the class files in the <code>.apk</code> file</dd>
98 <dt><code>mapping.txt</code></dt>
99 <dd>Lists the mapping between the original and obfuscated class, method, and field names.
100 This file is important when you receive a bug report from a release build, because it
101 translates the obfuscated stack trace back to the original class, method, and member names.
102 See <a href="#decoding">Decoding Obfuscated Stack Traces</a> for more information.</dd>
104 <dt><code>seeds.txt</code></dt>
105 <dd>Lists the classes and members that are not obfuscated</dd>
107 <dt><code>usage.txt</code></dt>
108 <dd>Lists the code that was stripped from the <code>.apk</code></dd>
111 <p>These files are located in the following directories:</p>
114 <li><code><project_root>/bin/proguard</code> if you are using Ant.</li>
116 <li><code><project_root>/proguard</code> if you are using Eclipse.</li>
120 <p class="caution"><strong>Caution:</strong> Every time you run a build in release mode, these files are
121 overwritten with the latest files generated by ProGuard. Save a copy of them each time you release your
122 application in order to de-obfuscate bug reports from your release builds.
123 For more information on why saving these files is important, see
124 <a href="#considerations">Debugging considerations for published applications</a>.
127 <h2 id="configuring">Configuring ProGuard</h2>
129 <p>For some situations, the default configurations in the <code>proguard.cfg</code> file will
130 suffice. However, many situations are hard for ProGuard to analyze correctly and it might remove code
131 that it thinks is not used, but your application actually needs. Some examples include:</p>
134 <li>a class that is referenced only in the <code>AndroidManifest.xml</code> file</li>
136 <li>a method called from JNI</li>
138 <li>dynamically referenced fields and methods</li>
141 <p>The default <code>proguard.cfg</code> file tries to cover general cases, but you might
142 encounter exceptions such as <code>ClassNotFoundException</code>, which happens when ProGuard
143 strips away an entire class that your application calls.</p>
145 <p>You can fix errors when ProGuard strips away your code by adding a <code>-keep</code> line in
146 the <code>proguard.cfg</code> file. For example:</p>
148 -keep public class <MyClass>
151 <p>There are many options and considerations when using the <code>-keep</code> option, so it is
152 highly recommended that you read the
153 <a href="http://stuff.mit.edu/afs/sipb/project/android/sdk/android-sdk-linux/tools/proguard/docs/index.html#manual/introduction.html">ProGuard
154 Manual</a> for more information about customizing your configuration file. The
155 <em>Overview of Keep options</em> and <em>Examples</em> sections are particularly helpful.
157 "http://stuff.mit.edu/afs/sipb/project/android/sdk/android-sdk-linux/tools/proguard/docs/index.html#manual/troubleshooting.html">Troubleshooting
158 </a> section of the ProGuard Manual outlines other common problems you might encounter
159 when your code gets stripped away.</p>
161 <h2 id="decoding">Decoding Obfuscated Stack Traces</h2>
163 <p>When your obfuscated code outputs a stack trace, the method names are obfuscated, which makes
164 debugging hard, if not impossible. Fortunately, whenever ProGuard runs, it outputs a
165 <code><project_root>/bin/proguard/mapping.txt</code> file, which shows you the original
166 class, method, and field names mapped to their obfuscated names.</p>
168 <p>The <code>retrace.bat</code> script on Windows or the <code>retrace.sh</code> script on Linux
169 or Mac OS X can convert an obfuscated stack trace to a readable one. It is located in the
170 <code><sdk_root>/tools/proguard/</code> directory. The syntax for executing the
171 <code>retrace</code> tool is:</p>
172 <pre>retrace.bat|retrace.sh [-verbose] mapping.txt [<stacktrace_file>]</pre>
175 <pre>retrace.bat -verbose mapping.txt obfuscated_trace.txt</pre>
177 <p>If you do not specify a value for <em><stacktrace_file></em>, the <code>retrace</code> tool reads
178 from standard input.</p>
180 <h3 id="considerations">Debugging considerations for published applications</h3>
182 <p>Save the <code>mapping.txt</code> file for every release that you publish to your users.
183 By retaining a copy of the <code>mapping.txt</code> file for each release build,
184 you ensure that you can debug a problem if a user encounters a bug and submits an obfuscated stack trace.
185 A project's <code>mapping.txt</code> file is overwritten every time you do a release build, so you must be
186 careful about saving the versions that you need.</p>
188 <p>For example, say you publish an application and continue developing new features of
189 the application for a new version. You then do a release build using ProGuard soon after. The
190 build overwrites the previous <code>mapping.txt</code> file. A user submits a bug report
191 containing a stack trace from the application that is currently published. You no longer have a way
192 of debugging the user's stack trace, because the <code>mapping.txt</code> file associated with the version
193 on the user's device is gone. There are other situations where your <code>mapping.txt</code> file can be overwritten, so
194 ensure that you save a copy for every release that you anticipate you have to debug.</p>
196 <p>How you save the <code>mapping.txt</code> file is your decision. For example, you can rename them to
197 include a version or build number, or you can version control them along with your source