HTML Minifier

What the HTML minifier does

Minifying HTML makes a page file smaller without changing what a visitor sees. Indentation, line breaks and comments help people read the markup, but browsers do not need them. This tool removes them, keeps everything that changes the page, and shows the size before and after in bytes, with the percent saved. With the inline options on, the CSS in style elements and the JavaScript in script elements are minified as well, with the same libraries as the CSS and JS minifier. To make minified HTML readable again, use the HTML formatter.

Which whitespace is safe to remove

MDN's guide to whitespace explains how browsers treat it with the default CSS: sequences of spaces collapse to a single space, spaces at the start and end of a line are removed, and a space right after another space is ignored, even across two inline elements. Block elements such as div, p and li each start their own line, so the whitespace between them is not shown. Between inline or inline-block elements it is: MDN notes that whitespace there results in spaces in the layout, like the spaces between words.

That gives the three whitespace settings:

• Collapse and trim turns every run of spaces, tabs and line breaks into one space, then removes that space where it touches a block element or the start or end of a block. Between inline elements, as in <b>a</b> <i>b</i>, the space stays.
• Collapse only turns every run into one space and never removes a space. It saves less, but it is safe for layouts that make list items or other block elements inline-block.
• Keep leaves all whitespace as it is, for when you only want to remove comments or minify inline code.

The content of pre, textarea, title, script and style is never changed by these settings. In pre and textarea every space and line break is shown, and script and style hold code that has its own rules.

Inline CSS and JavaScript

Style elements go through csso 5.0.5 (MIT license) and classic and module scripts through terser 5.51.2 (BSD-2-Clause license). Both load only when your HTML has a style or script element, and run in a background thread. Top-level names in classic scripts are not renamed, because other scripts and onclick attributes on the page may use them. JSON scripts, such as structured data in application/ld+json, lose only the whitespace between values; strings and numbers stay exactly as written. Script types the tool does not know, such as HTML templates, stay as they are.

Any block that cannot be minified safely is kept exactly as written and listed with its line: code with a syntax error, CSS that csso cannot fully read, JSON that does not parse, and scripts that contain <!--, which HTML parses in a special way inside a script.

What it does not do

• It does not remove quotes around attribute values, end tags that HTML lets you leave out, or default attribute values. Those save a few more bytes but are easy to get wrong.
• It does not change attribute values, including style attributes and event handlers like onclick, URLs or the words of your page. Only the spaces between attributes become one space.
• MDN notes that the DOM keeps whitespace text exactly as written. Removing it means fewer text nodes, so a script that walks every child node, text included, sees fewer of them.
• It does not know your CSS. If an element gets white-space: pre from a stylesheet, its whitespace is collapsed like any other.
• Tags that are not closed are listed under the result with their line, as the HTML formatter reports them. The output keeps exactly the tags you wrote.

A worked example

Press Fill in an example. The page has a doctype, a head with a comment and a style element, a paragraph with bold and italic words, a pre block with opening hours and a small script, formatted with two-space indentation: 742 bytes. With the default settings it becomes 464 bytes, 37.5% smaller. The comment is gone, #ff0000 became red, the script function's parameter became a single letter, and the pre block kept its three lines exactly. The space between "Save" and the bold 20% stayed, and the three spaces before "this week" became one. With inline CSS and JavaScript switched off, the result is 641 bytes, 13.6% smaller.

Limits

Files up to 10 MB can be opened and are read as UTF-8 text. Everything runs on your device, so very large pages take longer on phones and tablets. The preview shows the first 200,000 characters; Copy and Download include everything. Elements nested more than 1,000 levels deep are not minified. Always open the minified page and check it before you replace the live file.

How to use the HTML minifier

1. 1Paste your HTML, drop a file on the box or open one.
2. 2Choose how to treat whitespace and comments, and whether to minify inline CSS, JavaScript and JSON.
3. 3Read the result: bytes before and after, percent saved and any blocks kept as written.
4. 4Copy the HTML or download it as a .html file.

Sources

• MDN: Handling whitespace (collapsing, block elements and inline-block gaps)
• WHATWG HTML Standard: kinds of elements (void, raw text and escapable raw text elements)
• csso and terser on GitHub

Related guides

• JSON vs YAML vs CSV: Which Format for Which Job
• Core Web Vitals Explained: LCP, INP and CLS
• Cache-Control Explained: max-age, no-cache, no-store, ETag

Built by Tobias. Updated October 30, 2026.

Frequently asked questions