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Recaf

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What Recaf is

Recaf is a free, open-source Java bytecode editor for analyzing and editing compiled Java applications, as well as a tool for Java and Android reverse engineering. Users can inspect decompiled code, edit it as Java, and recompile classes into a workspace, or use the assembler to change JVM instructions. Recaf can attach to running Java processes and redefine classes without restarting them, but the Attach API does not allow removing existing fields or methods or adding new ones to existing classes. Search covers classes, members, strings, constants, references, and bytecode patterns. The software includes transformers for common obfuscation patterns, symbol-renaming tools, scripts, and plugins. It accepts class files, JAR, ZIP, WAR, and AAR archives, JMOD files, APK and DEX files, and read-only modules. Recaf runs on Windows, macOS, and Linux. It requires JDK 22 or higher and JavaFX 22 or higher; its launcher can download compatible JavaFX artifacts and offers GUI and CLI releases.

Who it suits

Recaf suits developers and analysts working with compiled Java or Android applications, including reverse engineering, malware analysis, modding, and live patching. Users need JDK 22 or higher and JavaFX 22 or higher.

What it does well

Edits decompiled Java or assembled JVM instructions.
Searches classes, members, strings, and bytecode patterns.
Supports scripts, plugins, and symbol renaming.
Attaches to running Java processes for class redefinition.

What to know first

Requires JDK 22 or higher.
Requires JavaFX 22 or higher.
Live patching cannot add or remove class fields or methods.

Limits

Recaf requires JDK 22 or higher and JavaFX 22 or higher. During live patching, the Attach API cannot remove existing fields or methods or insert new fields or methods into existing classes.

Getting started

Open the Recaf website and obtain a launcher release
Choose the GUI or CLI launcher
Select an installed Java version meeting JDK 22 or higher
Let the launcher download compatible JavaFX artifacts if needed
Open a supported class file, archive, APK, DEX file, JMOD, or read-only module

Verdict

Recaf covers inspection and modification across many Java and Android file formats, with search, plugins, and live class redefinition. Its Java requirements and limits on live patching are important to check before using it.

Questions

Does Recaf cost anything?

Recaf is free and open source, with a free plan and no trial requirement.

Which operating systems are supported?

Recaf supports Windows, macOS, and Linux.

What Java versions are required?

Recaf requires JDK 22 or higher and JavaFX 22 or higher. Its launcher can download compatible JavaFX artifacts.

Can Recaf patch a running application?

Yes. It can attach to running Java processes and redefine classes without restarting the target application. The Attach API cannot add or remove fields or methods in existing classes.

What files can it open?

Supported inputs include .class, .jar, .zip, .war, .aar, .jmod, .apk, .dex, and read-only modules.

Does it support extensions?

Yes. Recaf provides scripting and plugin support through modular APIs.

Facts from Recaf's own pages

Bytecode editing: Its assembler supports editing JVM instructions with labels, variable names, and bytecode snippets. · recaf.coley.software, 2 Oct 2026
Decompile and recompile: Users can view decompiled code, edit it as Java, and recompile classes into the workspace without adding dependencies to that workspace. · recaf.coley.software, 2 Oct 2026
Deobfuscation: Recaf includes transformers for common obfuscation patterns and tools for renaming symbols and inspecting specially crafted Java archives. · recaf.coley.software, 2 Oct 2026
Editing: Classes can be edited by recompiling decompiled code or reassembling disassembled code. · recaf.coley.software, 3 Oct 2026
File formats: Supported inputs include class files, JAR/ZIP/WAR/AAR archives, JMOD files, APK/DEX files, and read-only modules. · recaf.coley.software, 2 Oct 2026
Input formats: Recaf supports .class, .jar, .zip, .war, .aar, .jmod, .apk, .dex, and read-only modules, and auto-detects supported content types. · recaf.coley.software, 3 Oct 2026
Installation: The documentation recommends the launcher for most users; it downloads compatible JavaFX artifacts, lets users choose an installed Java version, and provides one-click updates. · recaf.coley.software, 3 Oct 2026
JavaFX requirement: Recaf requires JavaFX 22 or higher, which the launcher can download automatically. · recaf.coley.software, 3 Oct 2026
Java requirement: Recaf requires JDK 22 or higher. · recaf.coley.software, 3 Oct 2026
Launcher interface: Each launcher release offers a GUI and CLI. · recaf.coley.software, 2 Oct 2026
Live patching: Recaf can attach to running Java processes and redefine classes without restarting the target application. · recaf.coley.software, 2 Oct 2026
Live patching limits: The Attach API prevents removing existing fields or methods and inserting new fields or methods into existing classes. · recaf.coley.software, 2 Oct 2026
Obfuscation context: The documentation describes obfuscation as making application logic harder to reverse engineer and points to deobfuscation chapters for Recaf’s capabilities. · recaf.coley.software, 3 Oct 2026
Plugins and scripts: Recaf supports scripts and plugins through modular APIs, allowing users to automate workflows and extend functionality. · recaf.coley.software, 2 Oct 2026
Product: Recaf is an open-source Java bytecode editor for analyzing and editing compiled Java applications. · recaf.coley.software, 2 Oct 2026
Purpose: Recaf is a Java and Android reverse engineering tool for navigating application logic and modifying application behavior. · recaf.coley.software, 3 Oct 2026
Runtime requirements: Recaf requires JDK 22 or higher and JavaFX 22 or higher. · recaf.coley.software, 2 Oct 2026
Search: Search can find classes, members, strings, constants, references, and bytecode patterns. · recaf.coley.software, 2 Oct 2026
Use cases: The site lists reverse engineering, malware analysis, Java modding, and live debugging and patching as common use cases. · recaf.coley.software, 2 Oct 2026

Where Recaf stands on Freedom251

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