Code Minifier - Reduce JavaScript, CSS, and HTML File Sizes Online

Minify JavaScript, CSS, and HTML directly in your browser.

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Local-first
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Code Minifier helps reduce the size of JavaScript, CSS, and HTML by removing unnecessary whitespace, line breaks, and other non-essential characters.

It is useful for improving website performance, reducing file size, and preparing frontend assets for production environments.

All processing happens locally in the browser, which makes it practical for quick development tasks without sending code to an external service.

Common uses for Code Minifier

Typical tasks this tool is built for.

Minify JavaScript before deployment.
Reduce CSS file size for faster page loads.
Compress HTML markup for lightweight output.
Test minified code quickly during development.

How to use Code Minifier

Step 1. Select JavaScript, CSS, or HTML before pasting the source code into the input area.
Step 2. Adjust the available options for that language, such as Remove comments or Preserve important comments.
Step 3. For CSS or HTML, use Collapse whitespace only when you have checked that changing whitespace is acceptable for the source.
Step 4. For JavaScript, turn on Safe mode when you want Terser to skip compression and mangling; it still processes the entered source.
Step 5. Select Minify code, then review the generated output and the before-and-after size summary.
Step 6. Use Copy output or Download to take the current result into your project, then test it in its intended environment.

Why use this tool?

Minify pasted JavaScript, CSS, or HTML from one workspace with a language-specific output extension.
Use Terser for JavaScript, including its compression and mangling controls outside Safe mode.
Choose comment removal, important-comment preservation, and CSS or HTML whitespace collapsing where those controls apply.
Compare original and minified estimated UTF-8 sizes, saved percentage, and lines removed before copying the result.
Copy the current result or download it as output.min.js, output.min.css, or output.min.html.

Privacy and formats

Files and inputs stay in your browser during processing.

Input: TextOutput: Processed text

Best results with Code Minifier

Practical tips before you download or share the output.

Minification reduces file size, but it also makes code harder to read. Keep your original source code for editing and debugging.

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Common problems this tool helps with

Situations where this workflow saves time.

Minify code is unavailable - enter non-whitespace source text first.

JavaScript reports a failure - Terser could not parse the input or produce code, so check the source syntax and try again.

CSS or HTML output changes visible text or layout - whitespace collapsing and comment removal are text transformations, so inspect and test the result before using it.

You need to preserve a license or other important comment - enable Preserve important comments together with Remove comments; the preservation option is disabled otherwise.

You expect a source-file upload - this interface accepts pasted text and has no file-picker input.

The output is hard to debug - minification intentionally makes the result more compact, so retain the original source separately.

Copy output does not work - the browser clipboard API may be unavailable or blocked; select the read-only output text manually instead.

The downloaded file has the wrong type - select the intended language before minifying so the download uses its matching .min.js, .min.css, or .min.html extension.

Frequently asked questions

Which languages can Code Minifier process?

The language selector offers JavaScript, CSS, and HTML. The tool processes the text in the input area; it does not offer a file upload control.

How is JavaScript minified?

JavaScript is sent to the imported Terser minifier. Outside Safe mode, the component enables Terser compression and mangling; Safe mode passes both as disabled.

How are CSS and HTML minified?

The component applies its own text transformations: selected comment removal, trimming, and, when enabled outside Safe mode, whitespace collapsing. CSS also removes whitespace around several punctuation characters and a final semicolon before a closing brace.

Does minification always preserve code behavior?

No guarantee is implemented. The page itself advises testing production JavaScript, and CSS or HTML whitespace changes can be significant for particular source. Review and test the output before deployment.

What does Preserve important comments keep?

When comment removal is enabled, the HTML and CSS paths preserve comments beginning with an exclamation mark, and the JavaScript path passes a preservation pattern for comments marked with !, @preserve, @license, or @cc_on.

Can I copy or download minified code?

Yes. Copy output writes the current result through navigator.clipboard, and Download creates a plain-text download named output.min.js, output.min.css, or output.min.html according to the selected language.

Is there an input-size limit?

The component does not set an explicit character or file-size limit. Large pasted inputs can still be constrained by the browser and the selected JavaScript minifier.

What happens when I change languages or clear the tool?

Changing the language removes the current output, error, and copied state while leaving the entered input in place. Clear also removes the input text, and Load example replaces it with the selected language’s built-in example.

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How to use Code Minifier

Step 1. Select JavaScript, CSS, or HTML before pasting the source code into the input area.

Step 2. Adjust the available options for that language, such as Remove comments or Preserve important comments.

Step 3. For CSS or HTML, use Collapse whitespace only when you have checked that changing whitespace is acceptable for the source.

Step 4. For JavaScript, turn on Safe mode when you want Terser to skip compression and mangling; it still processes the entered source.

Step 5. Select Minify code, then review the generated output and the before-and-after size summary.

Step 6. Use Copy output or Download to take the current result into your project, then test it in its intended environment.

Why use this tool?

Minify pasted JavaScript, CSS, or HTML from one workspace with a language-specific output extension.

Use Terser for JavaScript, including its compression and mangling controls outside Safe mode.

Choose comment removal, important-comment preservation, and CSS or HTML whitespace collapsing where those controls apply.

Compare original and minified estimated UTF-8 sizes, saved percentage, and lines removed before copying the result.

Copy the current result or download it as output.min.js, output.min.css, or output.min.html.