Code Minifier Pro

A fast, offline CSS and JavaScript minifier for Windows.

Paste code, drop a file, or open one — then copy or save the minified result. No uploads, no accounts, no telemetry. Everything runs on your machine.

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Overview

Code Minifier Pro is a native WinForms desktop application that removes everything a browser or runtime does not need from CSS and JavaScript: comments, redundant whitespace, trailing semicolons, and other safe redundancies.

It is built for people who want a quick, local, dependency-free alternative to web-based minifiers — no code ever leaves the machine.

Why this project

• Fully offline. The application makes no network calls and has no third-party runtime dependencies.
• Syntax-aware, not regex-only. Strings, url(...), calc() expressions, CSS custom properties, JavaScript template literals, and regex literals are scanned and preserved instead of being blindly rewritten.
• Conservative by design. When a construct is ambiguous, the minifier keeps the safe form. Output is valid over being maximally small.
• Built for real files. A custom RichTextBox removes the default 64 KB text limit, and files over 50 MB trigger a confirmation prompt.
• Immediate feedback. Every run reports line counts, UTF-8 byte sizes, and the percentage saved.

Features

	CSS	JavaScript
Remove comments	Yes, except /*! ... */	Yes, except /*! ... */
Collapse whitespace	Yes	Yes
Preserve strings and URLs	Yes	Yes
Preserve license comments	Yes	Yes
Compute compression stats	Yes	Yes
Drag & drop a file	Yes	Yes
Open / save from disk	Yes	Yes
Copy to clipboard	Yes	Yes

Additional behavior:

• Automatic semicolon insertion safety — line breaks that could change JavaScript semantics are kept.
• Regex literal detection — /pattern/ is recognized after keywords and control-statement parentheses, so division and regex are not confused.
• CSS value optimizations — 0px → 0, 0.5 → .5, #AABBCC → #abc, hex colors lowercased, !important normalized.
• UTF-8 without BOM on save, with a BOM stripped on input if one is present.

Requirements

• Windows 7 SP1 or later (Windows 10/11 recommended)
• .NET Framework 4.8 runtime — included with Windows 10 (1903+) and Windows 11
• To build from source: Visual Studio 2022 with the .NET desktop development workload, or MSBuild 17+

Install

Download the release

1. Open the Releases page.
2. Download CodeMinifier-vX.Y.Z-win.zip.
3. Extract the archive and run CodeMinifier.exe. No installer is required.

The ZIP is portable: it contains the executable, its configuration file, the license, and this README.

Build from source

git clone https://github.com/kopolart/CodeMinifier.git
cd CodeMinifier
msbuild CodeMinifier\CodeMinifier.csproj /p:Configuration=Release

The executable is written to CodeMinifier\bin\Release\CodeMinifier.exe.

You can also open CodeMinifier.slnx in Visual Studio 2022 (17.13 or later) and build the solution.

Usage

1. Select the CSS or JS tab.
2. Add code in one of three ways:
   • paste it into the top editor,
   • drag a .css, .js, or .mjs file onto the editor,
   • click Open and choose a file.
3. Click Minify CSS or Minify JS.
4. Click Copy to place the result on the clipboard, or Save to write it to disk.

The status line below the buttons shows the number of lines before and after, the size in bytes before and after, and the percentage saved.

Examples

CSS

Input:

/* Card layout */
.card {
    padding: 0px 0.5rem;
    color: #AABBCC;
    background: url("img/icon.svg");
    transition: all 0.3s ease;
}

Output:

.card{padding:0 .5rem;color:#abc;background:url("img/icon.svg");transition:all 0.3s ease}

JavaScript

Input:

// Greeting
function greet(name) {
    return "Hello, " + name;
}

Output:

function greet(name){return"Hello, "+name;}

Minification rules

CSS

• Comments are removed; /*! ... */ license comments are preserved.
• Runs of whitespace collapse to a single space, which is then dropped around structural characters ({ } ; : , > ~).
• Trailing semicolons before } are removed.
• Selector text is protected: #Abc as an ID selector is never treated as a color, and a :hover keeps its descendant combinator.
• 0px-style zero values drop the unit for length units only. 0s, 0deg, 0fr, and 0% keep their units because removing them would produce invalid CSS.
• Leading zeros are removed from decimals (.5), hex colors are shortened when possible and lowercased.
• calc(), min(), max(), clamp(), env(), and var() are minified internally while preserving the mandatory spaces around + and -.
• Custom property values (--name: ...) are left untouched.
• url(...) contents, including data URIs, are never rewritten.
• // is not treated as a comment — unquoted URLs such as --api: https://example.com remain intact.

JavaScript

• Comments are removed; /*! ... */ license comments are preserved.
• Whitespace collapses to the minimum needed to keep tokens separate.
• Line breaks are retained wherever removing one could merge two statements under automatic semicolon insertion.
• Strings, template literals (including nested ${ ... } expressions), and regex literals are preserved verbatim.
• A division sign followed by a regex literal receives a separating space, so the output never accidentally becomes //.
• Parentheses belonging to if, while, for, and with are tracked so a / after the closing ) is read as a regex literal.
• Numbers support decimal, exponent, binary, octal, hexadecimal, bigint, and numeric separator forms.

Architecture

CodeMinifier/
├─ Program.cs                     Application entry point
├─ Controls/
│  └─ UnlimitedRichTextBox.cs     RichTextBox without the 64 KB limit
├─ Minification/
│  ├─ IMinifier.cs                Contract: Name + Minify(source)
│  ├─ CssMinifier.cs              Single-pass CSS minifier
│  └─ JsMinifier.cs               Single-pass JavaScript minifier
├─ UI/
│  ├─ MainForm.cs                 Window and language tabs
│  └─ MinifierTabView.cs          Reusable editor / actions / output view
└─ Properties/                    Assembly metadata and resources

Design principles

• Each language implements IMinifier, so adding a tab is a matter of implementing one interface and registering it in MainForm.
• The minifiers are single-pass character scanners with explicit state, not chains of regular expressions. This keeps them linear in input size and makes edge cases explicit.
• The UI is constructed in code without designer files, keeping the project small and reviewable.
• The application has no external dependencies beyond the .NET Framework itself.

Limitations

• The minifiers are scanners, not full language parsers or validators. Invalid input is not reported as an error.
• No identifier renaming, dead-code elimination, or AST-level optimization.
• No source maps, bundling, or transpiling.
• Output is deliberately conservative, so another minifier may occasionally produce smaller output.

Contributing

Contributions are welcome. Please read CONTRIBUTING.md before opening a pull request, and follow the Code of Conduct.

• Report a bug
• Request a feature
• Browse open issues

Security

Code Minifier Pro handles untrusted text and local files, so reports about crashes, corrupted output, or unsafe file handling are taken seriously. Please follow SECURITY.md and do not open a public issue for a vulnerability.

License

Released under the MIT License.

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_{Built with .NET Framework 4.8 and Windows Forms.}