// Free .NET Obfuscator - Basic Edition

Every major obfuscation algorithm.
Completely free.

Opaquer Basic gives you professional-grade .NET code protection at no cost - name obfuscation, string encryption, control flow, WPF/BAML shielding, and digital watermarking included. No trial. No expiry. No credit card.

⬇ Download Opaquer Free See what's included →

Opaquer Basic is a free .NET obfuscator for developers who want to protect .NET assemblies from decompilation and make reverse engineering more difficult. It provides a practical alternative to open-source .NET obfuscators and can be used with compiled C#, VB.NET, and other .NET applications without requiring the original source code.

Opaquer Basic - Protection Algorithms
ALL FREE
🔀
Private Name Obfuscation
Scrambles all private class, method, field, and variable names into unreadable tokens
Free
🏷️
Public Name Obfuscation
Renames public members - safe to use when they're not accessed from external assemblies
Free
🔐
String Value Encryption
Encrypts all hardcoded strings - API keys, SQL queries, secrets - hidden from static analysis
Free
🌀
Lightweight Control Flow
Restructures IL method bodies with fake branches and opaque predicates - decompilers produce garbage
Free
🎨
WPF / BAML Obfuscation
Encrypts compiled XAML resources - inspection tools can no longer expose your UI structure
Free
💧
Digital Watermarking
Embeds a tamper-resistant ownership signature - trace unauthorized redistribution of your binaries
Free
// Included in Basic

Professional protection,
zero cost

The Basic edition is not a crippled demo. Every obfuscation algorithm ships free. Here's what you get from day one.

🔀

Name Obfuscation

Replace every meaningful identifier - class names, method names, fields, properties, events - with randomized tokens. Optionally use non-printable characters that prevent recompilation of the deobfuscated IL entirely.

Private · Public · Internal - all free
🔐

String Encryption

Every string literal in your assembly - connection strings, license keys, SQL queries, URLs - is encrypted at build time and decrypted only at runtime. Static analysis tools see only opaque byte arrays.

AES-256 · 3DES · SHA-256 - all free
🌀

Lightweight Control Flow

IL method bodies are decomposed, reordered, and reassembled with opaque predicates and fake branches. The application behaves identically at runtime, but decompilers output unreadable or incorrect code.

Per-method granularity - free
🎨

WPF / BAML Protection

XAML compiles to BAML which is embedded in your assembly and trivially extractable. Opaquer encrypts these BAML resources so WPF inspection tools throw exceptions instead of revealing your UI layout and bindings.

Requires .NET 6+ and C# - free
💧

Digital Watermarking

Inject a persistent, tamper-resistant ownership signature into every protected assembly. If someone repackages or redistributes your software, the watermark stays embedded and detectable through Opaquer's interface.

Tamper-resistant - free
📦

All .NET Versions

Works with .NET Framework 1.0–4.8, .NET Core, and all modern versions: .NET 5, 6, 7, 8, 9, and 10. Opaquer protects any DLL or EXE published in a framework-dependent deployment.

.NET 8 · .NET 9 · .NET 10 - free
🖥️

Full GUI Interface

Browse your assembly's complete structure in a tree view. Select exactly which classes, methods, fields, and strings to protect. Save named settings profiles for fast re-use. No command-line knowledge required.

GUI + saved profiles - free
🗺️

XML Rename Map

After obfuscation, Opaquer outputs an XML file mapping every original name to its obfuscated token. Use it to decode stack traces and debug obfuscated builds without revealing the map to end users.

Debug-friendly - free
✍️

Assembly Signing

If your assembly is strong-name signed, Opaquer automatically re-signs the obfuscated output with your original key. You can also delay-sign or remove the signature for development scenarios.

Strong-name key support - free
// Transparent Limitations

Three things Basic doesn't include

No hidden restrictions on protection quality. The only three things that require a paid upgrade are about how and where you run the tool - not what it does to your code.

⚙️

Command-Line Interface (CLI)

The Basic edition is GUI-only. You open Opaquer, load your assembly, configure settings, and obfuscate manually. Automating obfuscation as a post-build step in Visual Studio or running it unattended in a CI/CD pipeline (Azure DevOps, GitHub Actions, etc.) requires the CLI - available in Pro and Enterprise.

Pro / Enterprise
👥

Team Deployment

A Basic license installs on a single PC. It's ideal for individual developers working alone. If multiple developers on a team need to run Opaquer - or if you want to share obfuscation profiles and settings across machines - you'll need an Enterprise license, which covers team deployment.

Enterprise
🔌

Internet-Free Build Server Support

Basic requires an internet connection for license validation. If your build infrastructure is air-gapped or operates behind strict network policies that prevent outbound connections, the offline build server mode is available in Enterprise.

Enterprise
// It Works

See what obfuscation does to your IL

The same free algorithms that ship in Basic transform your assembly's internals completely - without changing a line of source code.

Before - readable IL (decompilable in seconds)
1.class PaymentEngine
2{
3 .field _apiKey
4 .field _secretToken
5
6 .method ProcessPayment()
7 {
8 ldstr "sk_live_abc123..."
9 call ValidateKey
10 ret
11 }
12}

// Any decompiler reads this instantly
After - Opaquer Basic (non-recompilable IL)
1.class '?ÿ₁'
2{
3 .field '?₂ÿ'
4 .field '₃?ÿ'
5
6 .method '?ÿ₄'()
7 {
8 ldstr [ENC:0x9F3A…]
9 call '₅?ÿ'
10 ret
11 }
12}

// Cannot be recompiled - decompilers produce garbage

Name Obfuscation

Available in all editions · Free feature

Name Obfuscation replaces every visible identifier in your .NET assembly-types, methods, fields, properties, events, and nested members-with unreadable, meaningless tokens. Even though the names disappear, your application continues to run normally because the .NET runtime resolves members by metadata tokens rather than by their textual names.

Opaquer provides two independent naming modes: Non‑Standard Characters (default) and Non‑Displayable Characters (maximum protection). Both modes break the readability of decompiled output, but each serves a different purpose depending on your security requirements.

ILSpy – Before Obfuscation Original
Readable C# code before obfuscation, showing original class and method names.
The original assembly exposes every meaningful name. Any decompiler instantly reveals your architecture, business logic, and internal API surface.

ILSpy – After: Non‑Displayable Characters Protected
Decompiled code after obfuscation using Non‑Displayable Characters mode.
With Non‑Displayable Characters enabled, identifiers are replaced with characters that are illegal in C#, VB.NET, and even raw IL. Attackers cannot recompile the extracted IL, making reverse‑engineering attempts significantly more difficult.
ILSpy – After: Non‑Standard Characters (default) Protected
Decompiled code after obfuscation using Non‑Standard Characters mode.
Non‑Standard Characters (default mode): This mode replaces identifiers with short, random tokens that remain technically valid but carry no meaning. Decompilers can display these names, yet they provide no insight into your original logic. This mode is fast, stable, and ideal for most production applications.
Non-Displayable mode (free): Opaquer replaces identifiers with characters that are invalid in IL syntax. Even if an attacker extracts the obfuscated IL, they cannot reassemble it into working code - the names simply cannot be represented in any source language.
// Edition Comparison

What each edition adds

All obfuscation algorithms are identical across editions. Paid tiers add operational features for teams and automated pipelines - not stronger protection.

Feature Basic - Free Pro - $189.99 Enterprise - $489.99
Obfuscation Algorithms
Private name obfuscation ✔ Free ✔ ✔
Public name obfuscation ✔ Free ✔ ✔
Internal name obfuscation ✔ Free ✔ ✔
String value encryption ✔ Free ✔ ✔
Lightweight control flow obfuscation ✔ Free ✔ ✔
WPF / BAML obfuscation ✔ Free ✔ ✔
Digital watermarking ✔ Free ✔ ✔
XML rename map (for debugging) ✔ Free ✔ ✔
Assembly signing support ✔ Free ✔ ✔
High-intensity control flow ✘ ✘ ✔ Enterprise
Cloud code virtualization ✘ ✘ ✔ Enterprise
Operational / Deployment
Graphical User Interface (GUI) ✔ Free ✔ ✔
Command-line interface (CLI / CI-CD) ✘ Not included ✔ ✔
Team deployment (multiple PCs) ✘ Single PC only ✘ ✔
Internet-free build server support ✘ Not included ✘ ✔
Private Keys Depot (cloud KMS) ✘ ✔ ✔
Price $0 - Forever $189.99 lifetime $489.99 lifetime
// Get Started

Up and running in minutes

No installer wizard, no registration required for the Basic edition. Download, open, protect.

⚡

System Requirements

Windows 10 or 11 (64-bit) · .NET 10 runtime installed · Visual Studio 2010 or later (VS 2026 preferred) · 4 GB RAM · 20 GB disk

1

Download Opaquer.exe

Grab the free Basic release directly - no account required. If your antivirus flags it, temporarily disable it during download; this is common for obfuscation tools that manipulate IL. Mirror links available at opaquer.net.

2

Open your .NET assembly

Launch Opaquer and click Open Local EXE or DLL for Analysis. The GUI loads your assembly's full structure - namespaces, classes, methods, fields, and string values - in a browsable tree.

3

Configure protection settings

Choose name obfuscation scope, enable string encryption, select control flow intensity, and pick your naming mode (Non-Displayable for maximum hardening). Use the checkboxes to include or exclude individual members. Save as a named profile with F4.

4

Obfuscate and verify

Press F5 (or click Obfuscate). Opaquer outputs the hardened assembly and an XML rename map. Open the result in ILSpy or dotPeek - class names, method names, and strings should be completely unreadable.

5

Test your application

Run your full test suite against the obfuscated build. Pay attention to reflection-heavy code, serialization, and WPF data bindings. The XML rename map lets you trace any obfuscated identifiers back to originals for debugging.

⬇ Download Free Now Read Full Documentation
// FAQ

Common questions

Is the Basic edition really free forever - no trial period?
Yes. Opaquer Basic is free with no time limit, no project limit, and no feature expiry on any obfuscation algorithm. It installs on one PC and requires an internet connection for license validation, but there's nothing to pay. Rustemsoft monetizes through Pro and Enterprise upgrades for teams and CI/CD automation.
Why does Basic exclude the CLI if all the algorithms are free?
The CLI is an operational feature, not a protection feature. It enables unattended, automated obfuscation inside build pipelines - a requirement for teams and DevOps workflows. Rustemsoft includes it in Pro ($189.99 lifetime) as the first paid upgrade tier. If you obfuscate manually before each release, you'll never need it.
Can I use Basic for a commercial product?
Yes. Opaquer Basic is licensed for use on a single PC, and there's no restriction on the type of project you protect - open source, freeware, or commercial software. Review the full License Agreement for complete terms. The key constraint is single-machine installation: you cannot share a Basic license across a development team.
What's the difference between Lightweight and High-Intensity control flow?
Lightweight control flow (free) applies a moderate set of IL transformations - enough to make decompiler output unreadable for most purposes. High-Intensity control flow (Enterprise only) applies the maximum set of transformations and pairs with cloud code virtualization: critical method fragments are extracted, encrypted, and executed inside a secure VM at runtime. For the majority of .NET applications, Lightweight is more than sufficient.
Does obfuscation change how my app runs?
No - Opaquer's transformations preserve runtime semantics exactly. Your application behaves identically before and after obfuscation. The one exception to watch for: if your code uses reflection to load types or members by name at runtime (e.g. Type.GetMethod("MyMethod")), those names must be excluded from obfuscation, because the runtime will look for the original name. Opaquer's GUI lets you exclude individual members with a checkbox.
Does Basic support .NET 8, .NET 9, and .NET 10?
Yes. The Basic edition supports all .NET versions from Framework 1.0 through 4.8, plus .NET Core and every modern version: .NET 5, 6, 7, 8, 9, and 10. Opaquer itself requires .NET 10 installed on the machine running the tool; the assemblies it protects can target any supported version.
Can I obfuscate a WPF application with the free edition?
Yes. WPF / BAML obfuscation is fully included in the free Basic edition. Your compiled XAML resources are encrypted so inspection tools cannot reconstruct the UI structure. Two requirements: your WPF project must target .NET 6 or later, and it must be written in C# (VB.NET is not currently supported for WPF obfuscation).
What does "single PC only" mean in practice?
A Basic license activates on one machine. You can uninstall and move it to a different PC, but it cannot be installed on two machines simultaneously. If you have multiple developers who each need to obfuscate assemblies, or if you want obfuscation to run on a shared build server, you need an Enterprise license which covers team deployment.
When should I upgrade to Pro or Enterprise?
Upgrade to Pro ($189.99 lifetime) when you need to automate obfuscation in a CI/CD pipeline (Azure DevOps, GitHub Actions, post-build scripts) - that requires the CLI.

Upgrade to Enterprise ($489.99 lifetime) when any of these apply: multiple developers need Opaquer on their own machines; your build server has no internet access; you need maximum protection via High-Intensity control flow and cloud code virtualization.

If you're a solo developer shipping software manually, Basic covers you completely.
// Download Now

Start protecting your .NET code today

Every major obfuscation algorithm. No time limit. No credit card.

$0
Free forever · Single PC · All algorithms included
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