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Frequently asked answers to common questions and issues regarding JEB 3 and JEB 4. The last section is for questions regarding JEB 2, and is kept for reference only. All users are encouraged to migrate to the latest version of JEB.


Where is the end-user license agreement?#

The up-to-date end-user license agreement for JEB can be found here.

Can I generate license keys for additional machines?#

Yes, as long as the additional machines are operated by the licensee, they may install JEB on them. Contact licensing to request the ability to generate additional keys. We handle those requests promptly.

Can I revoke license keys?#

Yes, JEB license keys can be deprecated. Contact licensing to request key revocation. We handle those requests promptly.

I need to reinstall JEB on a different machine. Should I generate a new license key?#


Keys are specific to a user account. If you need to (re)install a non-floating build or the Controller for a floating build on a new system, make sure to generate a key on that system.

If you are planning to copy configuration files over, remove the .LicenseKey entry of jeb-client.cfg and generate a new key upon first run.

How do I check my license type, license identifier, or license key?#

From the command-line: execute JEB with the -c --license switches, eg:

$ jeb_wincon.bat -c --license

From the UI client: open the menu entry Help, About.

How do floating licenses work?#

Floating licenses work on a per-seat basis, as opposed to other license types that work on a per-user basis. Example:

  • A floating build valid for 3 seats allow any 3 users within your organization concurrently.
  • A non-floating build valid for 3 users allow 3 fixed, determined users to use JEB. No other user can use it.

Therefore, floating builds provide great flexibility for organizations where many users are planning to use JEB irregularly and/or at different times (e.g., teams split across various regions).

Please refer to this Manual entry to learn about setting up floating Controller and Clients.

What happens when my license subscription expires?#

JEB works on subscription. Past the expiration date, your software will continue to work and allow you to open and work on existing JDB2 projects, but you will not be able to create new projects.

Do subscriptions renew automatically?#

No. We do not perform auto-payments or auto-renewals. Please email sales when you need to renew a subscription.

Do you offer subscriptions valid for more than one year?#

Yes, we do offer custom subscriptions for up to 3 years. Email us at sales for details.

Do you offer perpetual licenses?#

No, we do not offer perpetual licenses at this point. However, we recommend you email sales and let us know your specific needs: we always strive to accommodate customers' needs.

Do you provide professional support?#

We do offer an additional support plan for JEB Pro and JEB Pro Floating licenses. Refer to the Buy page for details.

Do you offer large volume subscriptions?#

Yes, we do have plans for large enterprise and government. Those plans include the possibility to generate large amount of license keys. Reach out to sales for additional details.

We developed internal tools built around JEB. Can other users in my organization use them without breaking the EULA?#

Yes. As long as your JEB subscription is valid, users in your organization may access and use data produced by JEB.


Which version of Java shall I use to run JEB UI client?#

We recommend users to run the JEB client with a recent version of the Java, JDK 8 or above.

With Java 9 and above, the native launcher (jeb.exe on Windows, jeb on Linux, on macOS) may not run smoothly. If that happens, you can bypass the native launcher by using the -j flag with your start-up script. Example, on Linux: -j.

If you have installed multiple versions of Java, make sure to set the JAVA_HOME environment variable to the JDK of your choice.

The JEB client can always be started directly by executing jebc.jar on the command line: java -jar bin/app/jebc.jar

Which version of Java shall I use to run non-UI clients?#

The back-end components of JEB, jeb.jar, works with with any version of Java 8.191 or above.

Which build of the JDK should I use?#

Oracle builds or OpenJDK builds are preferred.

It seems some UI problems with GTK/Linux were caused by custom builds, such as JetBrains's JDK. Other problems, such as slowdowns and crashes during intensive processing, were reported by users using AdoptOpenJDK. For this reason, we strongly recommend to use Oracle/OpenJDK.

JEB complains that it "requires a Java runtime environment", although I have one installed.#

Your java binary should be accessible from the PATH environment variable. It is also recommended to set a JAVA_HOME environment variable pointing to your Java installation folder (bin/).

Make sure to install a 64-bit Java environment

A common source of problems are 64-bit systems having a 32-bit JRE accessible from the PATH or JAVA_HOME. You may have different versions of Java installed, but always make sure that paths refer to one that matches your system specifications.

How can I increase the maximum amount of memory usable by JEB?#

Edit the jvmopt.txt file at the root of your JEB folder. To increase the maximum amount of memory usable by JEB, adjust the -Xmx value.

Example: -Xmx8G: allow JEB to use up to 8 Gb of memory.

The settings in jvmopt.txt must be on a single line. After modifying this file, restart JEB with your usual start-up script. On start-up, a message in the logger output will reflect the updated capability:


Do not edit the configuration files buried in bin/app/... or bin/ folders. The memory settings in those files are automatically pulled from jvmopt.txt.


On which platforms can I run JEB?#

The UI desktop client runs on Windows (x64), Linux (x64, arm64), and macOS (x64, arm64).

The JEB back-end components, which can be used separately to build other clients or analysis pipelines, run on all systems for which a Java Runtime Environment version 8 or above is available.

What do I need to run JEB?#

The only external dependency is Java (JDK version 8 or above).

How can I run multiple instances of JEB?#

Multiple instances of JEB can run natively without configuration changes.

How can I redirect JEB logs to files on disk?#

Command-line runners, such as the floating license Controller or a script runner, can easily write log output to files. (Note that other clients, such as the UI desktop client, can do that via scripting - refer to GlobalLog.)

Use the --logfile=... flag. Consult the Usage info for additional details on that switch ("--help")

Example: Start a JEB Controller on Windows and log all INFO-level (or above) output to "controller.log.N" files (max. 5 rotating files, max. 2 Mb of log per file):

jeb_wincon.bat -c --controller --logfiles=controller.log,INFO,5,2

Does JEB run natively on Apple silicon? Is Rosetta 2 needed to run JEB on Apple Silicon machines?#

JEB (>=4.0-beta.4) can run natively on M1-powered (arm64) macOS systems. The Rosetta conversion system is not needed.


JEB messages and strings are in my current (non-English) locale. How do I switch to English?#

By default, JEB does its best to display messages in the current user's language settings. You may change the locale to English (or another one of the 10 supported languages) via the Edit, Language menu. See the Settings for details.

I am trying to debug an Android application, but my device cannot be found.#

JEB relies on the Android Debug Bridge (adb) to debug Android applications. Make sure to:

  • install the Android SDK (or at least have a stand-alone, working adb binary accessible from your PATH - some Linux distributions ship adb and other SDK platform tools in separate, leaner packages)
  • have the SDK path referenced in one of the following environment variables: ANDROID_SDK_ROOT (preferred) or ANDROID_HOME (legacy).

To troubleshoot your system, you may enable Developer Mode in your JEB options and examine the logger output. You will see lines like the following indicating how and where JEB is attempting to find adb:

[adb] ANDROID_HOME: Environment variable added to list of candidate Android SDK locations
[adb] ANDROID_SDK_ROOT: Environment variable NOT found
[adb] PATH: added to list of searched folders: (redacted)
[adb] Searching for 'adb.exe' in folders, by order: (redacted)
[adb] Found and using: C:\Users\nicol\AppData\Local\Android\sdk\platform-tools\adb.exe

Inside "Find text" widgets or filter fields, why are my regular expressions invalid or not working?#

JEB uses Java-style regular expressions, not PCRE, Boost, or other type of regex. Although the differences are minimal and subtle, complex regular expressions need to be carefully crafted and abide by the Java Pattern standard (refer to the "Comparison to Perl 5" section specifically).

I am using Ubuntu 16.04 LTS; the GUI behaves strangely and JEB closes unexpectedly.#

If you are using Ubuntu 16 with a recent version of JEB, the following error message may be reported in the console:

WARNING: GTK+ version too old (micro mismatch)
WARNING: SWT requires GTK 3.20.0
WARNING: Detected: 3.18.9

When trying to use menus and widgets, unexpected errors will likely happen, including program termination.

The reason is JEB 3.20+ UI framework (SWT) does not work properly with GTK 3.18-, used by Ubuntu 16: recent SWT builds require GTK 3.20+. In order to upgrade GTK without upgrading your entire distro to Ubuntu 18 or Ubuntu 20, you may use the following commands:

sudo add-apt-repository ppa:gnome3-team/gnome3-staging
sudo add-apt-repository ppa:gnome3-team/gnome3
sudo apt update
sudo apt upgrade

On Linux, I am seeing GTK error messages in the console.#

Most of those messages are harmless. If you are suspecting issues, please email support.

However, you may see the following message: "HoverWidget can not be loaded due to xxxxxxx because there is no underlying browser available. Please ensure that WebKit with its GTK 3.x bindings is installed (WebKit2 API level is preferred). Additionally, please note that GTK4 does not currently have Browser support. Is libwebkitgtk-1.0-0 package installed?". It indicates that some pop-up overlays will not work until you install libwebkit2gtk:

# find what version is available on your distro
apt-cache search libwebkit2gtk
# install the package (e.g. here, version 4.0.37)
sudo apt install libwebkit2gtk-4.0.37

I am using an old version of Ubuntu (18, 16), and JEB crashes or behaves strangely.#

A workaround is to start JEB with that environment variable set to avoid strange problems: GTK_DEBUG=no-pixel-cache

The easiest way to set this up once and for all is to export GTK_DEBUG=no-pixel-cache and then run


I work in a limited-connectivity environment, how can I update the software manually?#

The procedure i:

  • Check your registered email address for a JEB update email ("JEB xxx is available...")
  • Download the software archive
  • Copy the archive to the root of your JEB folder and rename the file to
  • Create a text file named update.pwd
  • Store the email-provided password inside this file
  • Start JEB as normal; the update will be installed automatically

I access Internet via a proxy. Can I still use JEB?#

Proxy settings can be stored at those two locations:

  • The UI client's settings, stored in jeb-client.cfg. If you are using the UI desktop client, they can be modified via the Options panel.
  • In headless mode, set the proxy settings in jeb-engines.cfg instead.

In each aforementioned configuration file, the network proxy data is stored as a key-value pair having the following format: .NetworkProxy = type|hostname|port|<username>|<password>|<whitelist>

  • Allowed types: http, socks.
  • 'username'/'password' can be left blank if your proxy does not require authentication
  • 'whitelist' is an optional, comma-separated list of wildcard hostnames/IPs to which JEB should always attempt to direct-connect (no proxy)

A few examples of valid proxy strings:

- http||8080
- http||8080||
- http||8080|||
- http||8080|||*
- socks||8088|user|pass|*


Do not forget the leading dot in .NetworkProxy!

How do I update from JEB n to JEB n+1?#

At the time of writing, you must install JEB n+1 (e.g. JEB 4) in a separate location. The auto-updater will only notify you that a JEB n+1 build is available for you to install. Check your email to download and install that new version.

Can I update from the command-line?#

Yes, you can run:

$ <jeb_startup_script> -c --check-update

After the update is downloaded, execute JEB normally.

JEB just auto-updated and I am now experiencing strange runtime issues. What can I do?#

If the issues you are experiencing are showing up after a software update, at seemingly random times during program execution, and involve error messages like "Error invoking method" or "Failed to launch JVM", it is likely that your last JEB update did not fully complete.

Try to execute your start-up script (eg, on Windows, jeb_wincon.bat) instead of any native launcher you may have been previously using (such as an OS desktop task bar shortcut).

If the issue is recurring, please email Support.


Why am I am seeing NullPointerExceptions and many Jython errors in the console when trying to execute a script?#

Make sure to use a JDK 11 or below. Although most components of JEB are compatible with JDK 8-14, Jython itself (used to execute JEB python scripts) currently requires JDK 8-11.

As of now (JEB version 3), and as said occasionally throughout this manual, it is better to run JEB using a recent JDK 8.

Can I execute a JEB Python script from the command line?#

Yes. Here's how to use the built-in script runner. You will need a Pro license.

  • Make sure your JEB scripts/ folder contains the jython-xxx.jar.
  • Execute your JEB startup script with --srv2 and --script parameters, as well as optional script arguments after --

Example on Windows:

$ jeb_wincon.bat -c --srv2 -- foo bar

Use -c --help to learn about other options.


Command-line arguments (in the example above: foo, bar) can be retrieved via IClientContext.


Alternate ways exist to run scripts or plugins in headless contexts. Read through this guide and associated sample code if you want to know more about writing your own front-end clients.

Can I write back-end extensions (plugins, contributions, etc.) in Python?#

Not at the moment. Back-end extensions should be written in Java (or any other language compiling to Java classfile, e.g. Kotlin).


Is there a public bug/feature tracker?#

Not at the moment. We are pretty responsive when it comes to answering users' queries though. Here's how to reach out:

JEB 2 (Legacy)#

(JEB 2) Can I run the JEB 2 desktop client on my 32-bit machine?#

Yes. Prior to JEB 3.0-beta.8, JEB UI can also run on Windows 32-bit and Linux 32-bit.

(JEB 2) Which version of Java shall I use to run JEB 2?#

The desktop client requires Java 8. The back-end components (jeb.jar) work fine with with Java 8 and beyond.

(JEB 2) How can I increase the maximum amount of memory usable by JEB?#

If unspecified, the memory cap is automatically decided upon starting up - and it will almost certainly be lower than what your system can offer.

In order to manually specify the maximum amount of memory usable by JEB, edit the file bin/jeb.ini located in your JEB folder. Add the following lines:


Replace ???? by the size amount of your choice, in Mb; eg, 4096 to allow JEB to use up to 4Gb. Note that other Java Virtual Machine options may be provided after the -vmargs (one option per line). Refer to the JVM manual for a complete list of options.

(JEB 2) I just upgraded to Java 8u131 or above (or Java 7u131), and JEB close immediately after start-up. What can I do?#

The probable reason is that you must be using JEB 2.2.10 or below. Older versions of JEB are no compatible with the newer JDK/SDK. There are two ways to solve this problem:

  • If you wish to stay on the JEB 2.2.x branch, install the latest update 2.2.11. You may use Java 7 or Java 8.

  • We recommend you upgrade to the latest version of JEB. Make sure to use Java 8 or above.

(JEB 2) How can I run multiple instances of JEB?#

Start your second and more instances of the UI client by using the -data @none command-line argument.

Example on Windows:

$ jeb_wincon.bat -data @none

Note that the customization of your UI workspace will not be ported over to this new instance, and will not be persisted upon closing either.

(JEB 2) JEB closes unexpectedly at start-up. How do I troubleshoot potential issues?#

By default, console messages generated by JEB are logged to the workspace/*log or workspace/.metadata/.log file within your JEB directory. If you are using the UI client, adding those settings to your bin/jeb.ini file will instruct the UI framework to log debug messages to the console:


Make sure to add them before any -vmarg parameter!

Restart JEB and examine the console log. If all else fails, please reach out to Support.

(JEB 2) How to execute a JEB Python script from the command line with JEB 2.3.4 (or older)?#

Here is how to run Python scripts in a headless environment with JEB 2.3.4 or older:

  • Make sure to drop a copy of Jython stand-alone JAR into your scripts folder
  • Navigate to your JEB folder, sub-folder bin/cl
  • Execute jeb.jar with --script and --libdir parameters, as well as optional script arguments (preceded by --)
  • Also remember to set up two Java properties, using -Dkey=value command-lines flags:
    • jeb.engcfg: points to your jeb-engines.cfg file
    • jeb.lickey: contains a valid JEB license key (such as the value referenced in .LicenseKey in your jeb-client.cfg file)


$ java -Djeb.engcfg=jeb-engines.cfg -Djeb.lickey=xxxxxxx -jar jeb.jar --libdir=xxxxx -- arg1 arg2 ...


The command-line arguments (arg1, arg2, ...) can be retrieved via IClientContext.

(JEB 2) I cannot find menu entry [xxx], where is it?#

You may need to reset the user interface state, via the Reset, UI State menu entry. A hard reset is to remove your workspace/ folder within your JEB installation folder.

(JEB 2) What are the views marked as "Unbound" in the UI Client?#

Those entries are layout placeholders from previous JEB sessions. They help JEB determine the best location to display a unit of a given type. (Note that "Unbound Views" can be closed at any time.)

In the example below, DEX views and Java Decompiled views would be opened in their corresponding placeholders before attempting to create additional views.