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JSDefender

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JavaScript Code Protection

JSDefender hardens JavaScript against reverse engineering, tampering, and unauthorized debugging.
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80% of Fortune 500 Dev Teams and Developers use PreEmptive.

The Global Standard for In-App Protection

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Why your JavaScript needs JSDefender?

Every line of JavaScript you ship is readable by default. Anyone with a browser can inspect your business logic, extract proprietary algorithms, and reverse engineer what took you years to build. JSDefender helps prevent that.
Protect what you’ve Built
Layered obfuscation makes it exponentially harder for bad actors to extract and replicate your business logic.
layered obfuscation
Tamper-Proof at Runtime
Detect unauthorized changes before they cause damage, and help keep your code behaving exactly as intended.
runtime protection, checks, integrity, against modification
No Entry for Unauthorized Debuggers
Disrupt any unauthorized attempt to debug, inspect, or probe your code interactively with DevTools.
debug protection

Security that compounds

The more layers, the harder it is to break in. JSDefender stacks protections so that bypassing one technique gets attackers nowhere.
Run only where you are allowed
Domain and date locking ensure your protected code runs only in authorized environments and within defined timeframes.
runtime environment protection
Make your logic unreadable
Control flow protection, function reordering, and structural transformations make your code harder to follow, reconstruct, or exploit.
prevent, stop reverse engineering
Keep sensitive values out of reach
Literal transformations and string extraction help ensure static inspection leaves attackers empty-handed.
string encryption
Active defenses at runtime
Tamper detection and DevTools blocking work continuously to disrupt runtime inspection and block unauthorized modification.
runtime protection, checks, integrity, against modification
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Trusted for flexible JavaScript protection
The on-premise obfuscation solution offered by the range of configuration choices was highly flexible and the integration process was simple. The outcome is a tool that precisely meets the needs of developers in our position and is easy to use and customizable.
— Satyaprakash S. , Antivirus Admin
As Reviewed on G2

See how JSDefender helps teams protect JavaScript with flexible, customizable controls.

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Protect your JavaScript application without breaking it

JSDefender rewrites your code into output that’s nearly impossible to reverse engineer, all while running exactly as intended.
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Try JSDefender on your own code

Run your sample JavaScript code through our free online obfuscator demo and see the difference yourself
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Start your free full-featured on-premise trial

Watch how JSDefender works

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Watch a quick overview of JSDefender - from applying protection settings to generating your first obfuscated build.

Frequently Asked Questions

JSDefender is available through PreEmptive plans based on the number of applications, users, and development teams you need to cover. Pricing is available by quote. View PreEmptive pricing or contact the team for a recommendation based on your development environment.

JSDefender licenses include access to product documentation, updates, and PreEmptive support engineers who can help troubleshoot issues and optimize your configuration. Specific response times and contractual SLAs may depend on your plan and agreement. Contact PreEmptive to confirm the support terms available to your organization.

Yes. JSDefender helps organizations in regulated industries protect sensitive application logic against reverse engineering, tampering, and unauthorized debugging. It can be integrated into existing build processes to apply protection consistently across releases. JSDefender can support a broader security and compliance program, but no individual tool makes an organization compliant on its own.

Free and open-source tools often focus on basic transformations, although their capabilities vary. JSDefender combines configurable code obfuscation with runtime defenses such as tamper detection, DevTools blocking, domain locking, and date locking. It also provides fine-grained configuration and repeatable integration with production build workflows. Like any protection tool, JSDefender does not make code impossible to reverse engineer—it increases the time, cost, and expertise required.

Yes. JSDefender performs protection within your development or build environment, so your source code does not need to be submitted to an online obfuscation service. It can run through the command-line interface or supported build-tool integrations, making it suitable for automated CI workflows. Standard JSDefender licensing currently requires an internet connection to validate the license whenever the product runs. Organizations with fully air-gapped requirements should contact PreEmptive to confirm whether their environment can be supported.

Yes. Code protected before the license expires will continue to run unless you configured a runtime restriction, such as date locking. An expired license prevents JSDefender from running, so you will not be able to protect new builds or rebuild existing applications until the license is renewed.

Applying protection can increase code size or add runtime overhead, depending on the transformations selected. JSDefender provides configurable and partial protection so teams can apply stronger defenses to sensitive business logic while excluding framework code or performance-critical sections. Protected builds should always be tested in a production-like environment before release.
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