Free · Fast · Privacy-first

HTML Formatter for JavaScript Projects

JavaScript projects produce HTML from many sources: JSX components rendered to strings, template literals interpolated into pages, server-side rendering pipelines emitting full documents, and headless browser captures of dynamically built DOM trees.

⚡

Format HTML output from any JavaScript framework

🔒

Verify server-side rendered HTML from Node.js apps

✨

Check HTML template literals by pasting their output

⚡

Free with no account needed

Cost: Free forever
Sign-up: Not required
Processing: In your browser
Privacy: Files stay local

FreeNo signupWhite-label

Add this HTML Formatter to your website

Drop the HTML Formatter into any page — blog post, product docs, intranet, school portal — with a single line of HTML. Your visitors get the full tool, processed entirely in their browser. No backend, no uploads, no signup.

Files stay 100% in the visitor's browser
Responsive — adapts to any container width
Free forever, no API key needed

Embed code

<iframe
  src="https://www.fixtools.io/html/html-formatter?embed=1"
  width="100%"
  height="780"
  frameborder="0"
  style="border:0;border-radius:16px;max-width:900px;"
  title="HTML Formatter by FixTools"
  loading="lazy"
  allow="clipboard-write"
></iframe>

<iframe
  src="https://www.fixtools.io/html/html-formatter?embed=1"
  width="100%"
  height="780"
  frameborder="0"
  style="border:0;border-radius:16px;max-width:900px;"
  title="HTML Formatter by FixTools"
  loading="lazy"
  allow="clipboard-write"
></iframe>

Attribution-friendly: a small "Powered by FixTools" link appears in the embed footer.

JavaScript Developers and HTML: Formatting Across the Stack

JavaScript developers encounter HTML in more places than developers who work with HTML directly. A typical web application generates HTML through JSX components in React, template literals in vanilla JavaScript, Handlebars or EJS templates in Node.js servers, htmx attribute responses from API endpoints, and HTML strings interpolated by hand in older codebases. In all of these contexts the HTML is the output of code rather than the input, which means formatting issues in the resulting markup are almost always symptoms of a code logic problem rather than direct editing mistakes. When the generated HTML looks wrong, formatting it is the first investigative step: it reveals the actual structure your code is producing, which is the prerequisite for figuring out why that structure differs from what you intended.

The fastest way to format HTML generated by JavaScript is to capture the output, paste it into FixTools, and review the formatted structure. This works for any JavaScript context: React component output captured with ReactDOMServer.renderToString, Express response output logged before res.send, Puppeteer or Playwright captures of the rendered DOM, or htmx response bodies inspected in the Network panel of the browser DevTools. The formatted result gives you a human-readable view of exactly what your JavaScript is producing, which you can then compare against your expected structure to identify missing wrapper elements, extra text nodes, incorrect nesting, or attribute generation bugs.

For teams that want to format HTML programmatically inside a JavaScript build pipeline, Prettier installed via npm is the most widely used JavaScript-native HTML formatter. Prettier integrates with every major build tool, runs as a pre-commit hook, and produces output that matches the same conventions FixTools uses. The two tools are complementary: use FixTools for quick visual inspection during debugging or exploration, and use Prettier for automated formatting enforcement as part of your build or commit pipeline. The output from both is interchangeable for standard HTML, so you can develop and verify with FixTools and enforce with Prettier without worrying about consistency between them.

There is a deeper point about working with generated HTML that is worth naming. When you read code that generates HTML, you are reading the rules for producing the output rather than the output itself, and these are very different mental models. Formatting the actual generated output reconnects you with what your code is producing in the world, not what your code looks like it should produce when you read its source. This reconnection step is one of the most valuable debugging habits a JavaScript developer can build, and a fast browser-based formatter makes it cheap enough to do constantly throughout the workflow rather than only when something obviously breaks.

Prettier HTML formatting MDN: DOMParser API

How to use this tool

💡

Paste HTML output from your JavaScript application and click Format. The formatted output lets you verify the structure your code is generating.

How It Works

Step-by-step guide to html formatter for javascript projects:

1
Capture your JavaScript-generated HTML
Get the HTML string from your JavaScript using renderToString for React, by logging the template output for Handlebars or EJS, or by copying from the DevTools Elements panel for live DOM inspection.
2
Paste into FixTools
Paste the HTML string into the FixTools HTML Formatter input panel. The tool accepts any size from a single component output to a complete page render.
3
Click Format
Click Format to produce a readable, indented version of the generated HTML. The result appears within milliseconds and shows exactly what your JavaScript is producing.
4
Review and compare
Review the formatted output against your expected structure to identify generation errors. The formatted view makes structural discrepancies stand out clearly compared to reading the original compressed output.

Real-world examples

Common situations where this approach makes a real difference:

Debugging unexpected HTML from a React SSR component

A Next.js page produces a hydration mismatch warning in the browser console after a deploy. The developer formats the server-side rendered HTML in FixTools, formats the client-side DOM as captured from DevTools, and compares the two. The formatted comparison reveals an extra wrapping div added server-side that is absent client-side, identifying the source of the mismatch within minutes rather than the hours that line-by-line comparison of compressed HTML would have required.

Verifying Express.js template output matches design spec

An Express server uses EJS templates to render a product detail page. After adding a new pricing section to the template, the developer captures the rendered HTML, formats it in FixTools, and confirms that the new section renders with the correct class names, the expected element hierarchy, and the proper schema markup before deploying. The formatting pass catches a missing closing div that would have broken the page layout in production.

Formatting API response HTML for documentation

A Node.js API returns HTML fragments for an htmx-driven frontend. The documentation team formats representative example responses in FixTools and includes the formatted versions in the API reference. Developers integrating against the API report fewer confusion-driven support questions in the months after the documentation update because they can see the response structure they need to handle.

Auditing a legacy jQuery-rendered component

A legacy jQuery component builds HTML by concatenating strings with template-style placeholders. The developer captures the rendered output and formats it in FixTools, discovering that the component is producing three nested div levels more than necessary because of how the string concatenation accumulated wrappers over years of edits. A refactor removes the unnecessary wrapping without changing any rendered output, reducing the DOM size and improving CSS performance.

When to use this guide

Use this when you are a JavaScript developer who needs to format HTML produced by your code, inspect template output, or verify that your HTML generation is producing correct structure.

Pro tips

Get better results with these expert suggestions:

Format React component HTML output to debug rendering

When a React component renders unexpected HTML, capture the output with renderToStaticMarkup and paste it into FixTools. The formatted view shows the exact HTML your component is producing, which makes it straightforward to spot missing wrapper elements, incorrect nesting from conditionally rendered children, or unexpected text nodes from interpolated whitespace. This approach often solves component output bugs faster than reading the component source, because it focuses on the actual output rather than the rules that produced it.

Compare formatted Handlebars template output to your Figma design

Capture the HTML output of a rendered Handlebars or EJS template, format it in FixTools, and compare the structure against your design's component hierarchy in Figma. This is much faster than tracing the template logic by hand, particularly for templates with substantial conditional logic or many partials. Structural discrepancies between the design and the generated output become immediately obvious in the formatted result.

Use formatted HTML to write accurate Playwright selectors

When writing end-to-end tests for a JavaScript application, format the page HTML output in FixTools before writing your test selectors. The formatted structure shows the exact nesting of elements you need to traverse, which makes it straightforward to write reliable CSS selectors, XPath expressions, or accessibility-based queries. Tests written against formatted reference HTML tend to be more reliable than tests written against the live DOM because the formatted reference is stable across runs.

Format HTML from headless browser captures for debugging

When using Puppeteer or Playwright to capture page HTML for analysis, paste the captured output into FixTools and format it. Headless browsers return the full rendered DOM including dynamically injected content from JavaScript frameworks, and the formatted view makes it easy to identify which elements are part of your initial HTML and which were inserted by client-side scripts. This distinction is hard to make in compressed output and obvious in formatted output.

Capture React component output for formatting

Use ReactDOMServer.renderToString() or renderToStaticMarkup() to get the HTML string output of a component, then paste it into FixTools to verify the structure your component is generating.

Format HTML from template literals

Copy the string value of an HTML template literal (e.g., by logging it to the console), paste it into FixTools, and format it to see the generated structure clearly.

Use Prettier for automated HTML formatting in CI

For automated formatting in a JavaScript build pipeline, use Prettier with the HTML parser. FixTools is ideal for quick visual inspection; Prettier is the right choice for enforcing formatting in automated workflows.

FAQ

Frequently asked questions

JSX is not valid HTML and should not be pasted directly into FixTools. The differences between JSX and HTML, including self-closing tag syntax, the className attribute, and the camelCase event handler names, mean JSX would format inconsistently or produce errors. For formatting JSX in your source code, use Prettier with JSX support configured in your editor. If you want to inspect the HTML output of a JSX component, capture the rendered output using ReactDOMServer.renderToStaticMarkup, and paste that HTML string into FixTools for formatting.

In a Node.js context, import renderToStaticMarkup from react-dom/server and call it with your component element: renderToStaticMarkup(<MyComponent prop="value" />). The return value is an HTML string ready to paste into FixTools. In the browser, you can either use the same function from react-dom/server in a script, or copy the rendered element's outer HTML directly from the Chrome DevTools Elements panel by right-clicking and selecting Copy outer HTML.

FixTools formats pure HTML. If you have a Handlebars or EJS template file containing template syntax such as {{variable}} or <% if (condition) { %>, you have two options. First, paste the raw template directly and FixTools will format the surrounding HTML while preserving the template tags as text; this works well for templates with simple inline expressions. Second, render the template with sample data to produce pure HTML output, and paste the rendered result; this works better for templates with substantial control flow logic.

Prettier is the most widely used and most actively maintained. Install it with npm install prettier and format HTML files with npx prettier --write "**/*.html" or use the programmatic API as prettier.format(htmlString, { parser: "html" }). For HTML formatting within a build pipeline, Prettier integrates with webpack, Vite, Rollup, esbuild, and essentially every other modern build tool through documented plugins or simple command-line invocation as part of the build script.

JavaScript template literals are not processed by FixTools because the tool expects pure HTML input. For formatting HTML inside template literals in your editor, the Prettier VS Code extension with the embeddedLanguageFormatting option enabled handles this case, formatting the HTML inside tagged template literals such as those used by lit-html, lit-element, or hand-tagged html template literal helpers. The lit-plugin VS Code extension provides additional formatting support specifically for lit-html template syntax.

Yes, this is one of its highest-value uses for JavaScript developers. Paste the HTML output of your JavaScript generation code into FixTools and review the formatted structure. Compare it to your expected structure to identify missing elements, incorrect nesting, extra wrapper divs from over-cautious conditional rendering, or attribute generation errors from mistyped template variables. This output-focused debugging is often faster than tracing through the generation code by hand, particularly for complex components with many code paths.

FixTools and Prettier produce equivalent output for standard HTML because both target the same widely-adopted conventions. FixTools is faster for one-off visual inspection during debugging because pasting into a browser tab is quicker than running a command-line tool. Prettier is better for automated enforcement in a build pipeline because it integrates with your version control hooks, CI pipeline, and editor save handlers. Use FixTools for quick interactive checks and Prettier for ensuring every commit lands in a consistently formatted state.

Yes, HTML produced by Next.js, Nuxt, Remix, SvelteKit, Astro, and other server-side rendering frameworks is standard HTML5 markup and formats correctly in FixTools. Paste the rendered output from the page source, from a server log of the response body, or from a renderToString call captured in a test, and the formatter will produce a clean indented version. This is particularly useful for debugging hydration mismatch warnings, where comparing the server-rendered and client-rendered output requires both to be readable.

Most modern build tools support an option to emit unminified output for debugging. Configure your build to emit unminified HTML, capture a representative file from the output directory, and format it in FixTools to inspect the structure. This is particularly useful when debugging differences between development and production builds, where the production output is normally minified and impossible to read directly. The unminified-plus-formatted combination gives you full visibility into what your build is producing.

For snapshot tests that compare HTML output, yes. Use Prettier or a similar formatter to normalize both the expected and actual HTML before comparing, so that snapshot diffs reflect real structural changes rather than incidental whitespace differences between runs. The same principle applies to any test that asserts on HTML strings: normalize the format before comparing, and the tests become more reliable and the failure messages more useful. FixTools can serve as the reference for what the normalized format should look like. JavaScript-based formatters integrate well with React, Vue, and Angular component development pipelines.

Prettier with its HTML plugin is the most widely adopted formatter, used by major frameworks including Next.js, Remix, and many Vue projects. js-beautify is a lighter-weight option with HTML/JS/CSS support, often used in browser-based tools. html5parser provides parsing primitives if you want to build custom formatting. For React-specific formatting, Prettier with JSX support handles both component code and embedded HTML consistently. Choose Prettier for production projects where consistency across contributors matters, and js-beautify for tools that need to embed formatting logic with minimal dependencies.