Compare DLL Files Online

The only online tool that decompiles two .NET DLLs to C# source and diffs the actual code. No installation required.

.dll

1st File

Drop 1st .dll file here
Choose file

2nd File

Drop 2nd .dll file here
Choose file

How It Works

1

Upload

Drop old and new versions of your .dll file into the upload areas.

2

Decompile

Both DLLs are decompiled to C# source code using ILSpy.

3

Diff

View a file-by-file diff of every changed class, method, and interface.

What is a .NET DLL File?

A .NET DLL (Dynamic-Link Library) is a shared library containing compiled C# or VB.NET code in Intermediate Language (IL) format. Unlike native C/C++ DLLs, .NET DLLs can be decompiled back to readable source code. NuGet packages, Unity plugins, and most .NET libraries are distributed as DLL files.

Why Compare DLL Files at the Source Level?

When upgrading .NET libraries or auditing third-party dependencies, you need to know what actually changed in the code, not just that the file size differs.

This tool decompiles both DLL assemblies to C# source and generates a unified diff. You see exactly which public APIs changed, which internal logic was modified, and which types were added or removed. Use it for:

DLL Diff Tool vs. Other Options

Desktop tools like JustAssembly (Telerik), BitDiffer, and dotPeek can compare .NET assemblies but require local installation. ILSpy and dnSpy can decompile DLLs but don't offer built-in diff functionality. Generic online diff tools like Diffchecker cannot handle binary DLL files at all. This is the only online tool that decompiles .NET DLLs to C# and shows a unified source diff.

Frequently Asked Questions

How do I compare two DLL files?

Upload the original DLL on the left and the modified DLL on the right. Both files are decompiled to C# source code using ILSpy, then a unified diff is generated showing every changed class and method.

What types of DLL files can be compared?

This tool supports .NET (C#/VB.NET) DLL assemblies. Native C/C++ DLLs are not supported. The DLL must be a managed .NET assembly to be decompiled.

What decompiler is used for DLL files?

DLL files are decompiled using ILSpy (ilspycmd), which converts .NET IL bytecode back to C# source code.

Can I compare NuGet package DLLs?

Yes. Open each package in the NuGet viewer, download the matching implementation DLL from the same target framework, and upload those two DLLs here. Package-to-package diff is not supported.

How do I diff NuGet package updates?

Inspect each .nupkg with the NuGet viewer, download the corresponding DLLs from the same framework folder, then compare those DLLs here. This compares recovered assembly source, not whole packages.

Is it free?

Yes, completely free. No registration or installation required.

Is my file safe?

Yes. Uploaded files are stored temporarily for decompilation and comparison, then automatically deleted. Files are never shared with third parties.