HTML
Minifier
Remove comments, collapse whitespace, and reduce your HTML file size. Fast, free, and entirely in your browser.
How It Works
Paste HTML
Paste or type your HTML code into the input area.
Minify
Click Minify to remove comments and collapse whitespace.
Copy or Download
Copy the minified code or download it as an .html file.
Minify HTML online to reduce page weight, save bandwidth, and improve Core Web Vitals scores. ConverterUp's HTML minifier removes whitespace, comments, redundant attributes, and unnecessary quotes while keeping the document structurally valid. Front-end developers and static-site builders can paste their template, click minify, and ship a smaller payload to production. Minification runs in your browser using a deterministic parser, so proprietary markup, internal templates, and unreleased landing pages stay completely private.
What gets removed during minification
Whitespace is the biggest win. Hand-written HTML and template-engine output contain hundreds of newlines, tabs, and runs of spaces that the browser never renders. The minifier collapses every whitespace sequence to a single space (or removes it entirely between block-level elements), typically shaving 15–25 % off raw size before gzip.
Comments (<!-- ... -->) are stripped except for conditional comments (<!--[if IE]>), which carry semantic meaning for legacy IE rendering. Server-side directives in some template engines (e.g., <!--#include --> for SSI) are detected and preserved. Comments inside <script> tags follow the script-minification rules, not the HTML rules.
Optional tags per the HTML5 spec — the closing </li>, </p>, </tr>, </td>, and several others — can be safely omitted because the parser infers them. Same for <html>, <head>, and <body> opening tags in many positions. Aggressive mode removes them; safe mode keeps them for editor compatibility.
Redundant attributes get collapsed: type='text/javascript' on <script> (default in HTML5), type='text/css' on <style>, language='javascript', method='get' on forms. Unnecessary quotes get removed when the attribute value contains no special characters: class='btn' becomes class=btn. Boolean attributes get collapsed: disabled='disabled' becomes disabled.
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When NOT to minify HTML
Never minify the file you commit to source control. Minified HTML is unreadable, undiffable, and impossible to review in a PR. Keep the source template human-readable and minify only the build artifact that goes to the CDN. The same rule applies to email templates, MJML output, and JSX/template engine output.
Skip minification during local development. Source maps for HTML do not exist (unlike JS/CSS), so a broken minified template is much harder to debug than a broken source template. Most dev servers (Vite, Next.js, Astro) serve unminified HTML in development and minify only in production builds.
Avoid minifying inside template engines that depend on whitespace semantics. Liquid, Handlebars, EJS, and Jinja generally tolerate whitespace removal, but Pug/Jade and Slim are whitespace-sensitive by design — minifying their output post-render is fine; minifying the template itself is destructive. Same for Markdown and MDX sources.
Be careful with <pre>, <textarea>, and white-space: pre CSS. Content inside these elements preserves whitespace semantically — a code block in a blog post relies on every space and newline. ConverterUp detects these blocks and skips whitespace collapse inside them. If you use a custom element with CSS-controlled whitespace preservation, the minifier cannot know that without explicit configuration.
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Build pipeline integration: where this fits
For one-off minification (a single template, an HTML email, a static landing page generated by a no-code tool), paste-into-ConverterUp is the fastest path. For ongoing production sites, minification belongs in the build step. Doing it manually after each deploy is error-prone and skips the source-map benefits.
Next.js, Astro, and Gatsby minify HTML automatically in production builds via html-minifier-terser. SvelteKit and Nuxt do the same. If you use these frameworks, the static output is already minified — paste-minifying again gains nothing. Webpack users add html-webpack-plugin with minify: true. 11ty users add an HTML transform that pipes the output through a minifier.
Server-rendered apps (Rails, Django, Laravel, Express + EJS) usually do not minify by default. The win from minifying server-rendered HTML is real (10–25 % on first-byte size) but small once gzip/brotli kicks in. Most teams skip it because the build complexity outweighs the byte savings on TLS+brotli connections.
Don't compare apples to oranges: a minified HTML file is smaller on disk, but the network savings after gzip/brotli are often only 2–5 % because compressors already deduplicate runs of whitespace. Minify to improve parse time in the browser more than to save bandwidth — the browser still has to read every byte, and stripping comments + optional tags speeds up the HTML parser noticeably on slow devices.
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Frequently asked questions
How much can HTML usually be minified?
Typical reductions are 15-30 % for hand-written HTML and up to 50 % for documents with heavy whitespace and HTML comments. Combine with gzip or brotli compression for additional savings on the wire.
Does minification break inline JavaScript or CSS?
No. Inline scripts and styles are preserved verbatim by default. Enable the aggressive option to also minify them, which collapses whitespace inside script and style tags.
Will conditional comments and IE hacks be kept?
Yes. Conditional comments such as <!--[if IE]> are detected and preserved because they carry browser-specific logic. Standard comments without semantic meaning are stripped.
What is the maximum HTML size?
Documents up to 5 MB are processed in well under a second. Larger files still work but the editor may feel sluggish; consider minifying as part of your build pipeline for production sites.
Does minifying HTML hurt SEO or accessibility?
No, when done correctly. Search engines parse the DOM after the browser parses HTML, so whitespace and comments are invisible to them. Accessibility is unaffected because <code>aria-*</code> attributes, <code>alt</code> text, semantic tags, and the rendered text are all preserved. Only the bytes change.
Can I minify Handlebars, EJS, or other templated HTML?
Yes, with caveats. ConverterUp's <em>'preserve template syntax'</em> mode leaves <code>{{ }}</code>, <code><%= %></code>, <code>{% %}</code>, and similar delimiters intact, including the whitespace inside them. Whitespace <em>around</em> the template tags is still collapsed, which is safe in 99 % of cases. For whitespace-sensitive templates (Pug, Slim), minify the rendered output instead of the source.
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