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HTML Prettifier Online

A prettifier is the simplest possible interface to a complex operation.

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One-click prettification with sensible defaults

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Works with fragments and full pages

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Handles inline scripts and styles correctly

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Runs in your browser with no upload

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

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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.

What an HTML Prettifier Does and Why Simple Is Better

A prettifier turns markup that is technically valid but visually noisy into markup that a human can scan and edit. The transformation is purely cosmetic: tags, attributes, content, and embedded scripts are preserved exactly while whitespace and indentation are normalised. The output renders identically to the input in any browser because whitespace between block-level elements has no visual effect. The value of the operation is entirely in how much easier the markup becomes to work with afterwards. A prettifier is the right tool when you are reading HTML, not when you are deploying it; for deployment, run a minifier on the prettified output as the last step of the build.

FixTools defaults to two-space indentation because that is the modern convention used by Prettier, the Google HTML and CSS Style Guide, and most open-source front-end projects. The default exists so that the tool produces the right output for the most common case without any user input. If you need four-space indentation for a project that uses it, the option is available, but you should not need to think about it until you actually have a reason to change it. Defaults that match the most common case are how utility tools stay useful; configuration that nobody uses is friction without benefit.

The simplicity of the interface is a deliberate design choice rather than an oversight. There are HTML formatters with dozens of options for line wrapping, attribute placement, comment handling, and embedded language behaviour. Those options matter for specific use cases, but for the typical case of making HTML readable they are noise. By choosing sensible defaults and presenting one button, the prettifier removes the cognitive load of evaluating options every time you want clean HTML. The result is a tool you can use without thinking, which is exactly what you want when you are trying to focus on the actual problem you are solving rather than on the configuration of your formatting tool.

A subtle benefit of one-click prettification is that the output is reproducible. Anyone else who pastes the same input into FixTools gets the same output, because there are no per-user settings that change the result. This matters when you share a formatted snippet with a colleague who wants to verify the formatting or contribute back; their version will match yours exactly, with no merge noise from differing formatter settings. Reproducibility is a feature of conservative defaults, and it pays back many times over the slight cost of not having every possible configuration knob exposed.

HTML Living Standard (WHATWG)W3C Markup Validation Service

How to use this tool

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Paste your HTML and click Format. The output appears immediately with two-space indentation and clean structure, no configuration required.

How It Works

Step-by-step guide to html prettifier online:

1
Paste your HTML
Paste any HTML into the input panel. Fragments, full pages, generated output, and copied snippets are all handled identically.
2
Click Format
Click Format to apply the default two-space indentation. The output appears in the output panel immediately.
3
Read or copy
Read the prettified output directly or copy it to your clipboard with one click. The original input remains in the input panel for further passes if needed.

Real-world examples

Common situations where this approach makes a real difference:

Reading a stack trace HTML response

A developer pastes a 500-error HTML page into FixTools to find the actual stack trace buried inside the error page markup. The prettified view reveals the structure immediately, making the stack trace location obvious rather than requiring careful manual scanning of compressed output.

Preparing markup for a teaching example

An instructor preparing a workshop slide pastes a one-line HTML example into FixTools to produce a properly indented version for inclusion in the slide. The prettified output displays clearly in the slide deck without manual line-breaking, and students can copy it directly into their own editors during the exercise.

Quick check on copied competitor markup

A product manager copies a section of competitor HTML to understand a layout pattern. The original is compressed; the prettified version makes the pattern obvious within seconds, allowing the PM to write a structured product brief about the pattern rather than describing it vaguely.

Fixing a broken email signature

A user pastes their email signature HTML into FixTools after the formatting in their email client started looking off. The prettified output shows a stray closing div that crept in during a recent edit. Removing it fixes the signature in one targeted change rather than the broad rewrite the user was about to attempt.

When to use this guide

Use this when you want clean, indented HTML with no configuration choices to make. The default settings produce the right answer for almost every input.

Pro tips

Get better results with these expert suggestions:

Use the prettifier as the universal first step

Make prettifying the default first action whenever you encounter unfamiliar HTML, regardless of the eventual goal. Whether you plan to edit, audit, document, or just read, the prettified version is more useful than the original for every subsequent operation. The cost of a click is negligible compared to the time it would take to read compressed markup, and the habit removes the moment of friction where you have to decide whether the formatting step is worth it. Default to prettifying first; revisit the decision only if the source is already perfectly formatted.

Treat the prettifier as a sanity check after generation

When generating HTML programmatically, paste the generated output through the prettifier as a sanity check. The prettified output makes structural errors immediately visible: missing closing tags, accidentally nested headings, duplicate IDs, and so on. Generators that produce technically valid but structurally wrong HTML are surprisingly common, and a five-second pass through the prettifier catches these issues before they reach test or production.

Use prettification for HTML embedded in JSON

When debugging API responses that include HTML strings inside JSON payloads, extract the HTML string, unescape any JSON-specific escaping, and paste through the prettifier. The structural view of the HTML reveals whether the server is producing the expected markup, which is often the actual bug you are looking for. Diagnosing HTML-in-JSON without prettification requires reading escaped compressed markup, which is one of the hardest reading tasks in web development.

Combine prettification with diff for incremental edits

When making a small edit to a large HTML file, prettify both the before and after versions and diff them to confirm the change is exactly what you intended. The diff of prettified output is small and obvious, while the diff of unformatted output can be a large blob that hides the actual change. Prettifying both sides of a diff is a quick way to verify that you did not accidentally introduce unintended changes during the edit.

Use it for quick reads

A prettifier is ideal when you just want to read HTML clearly. Skip the configuration and use the default settings; they are right for the common case.

Bookmark it for one-click access

Bookmark the prettifier so it is always one click away when you receive unformatted HTML. The fewer steps between you and clean output, the more often you will actually format.

Share the prettified version

When asking a colleague about a markup issue, share the prettified version rather than the original. The conversation moves faster when both of you can read the code immediately.

FAQ

Frequently asked questions

The terms are interchangeable in practice. Both refer to a tool that takes unformatted HTML and returns it with consistent indentation applied. Some tools use prettifier to emphasise the simplicity of the operation, while beautifier emphasises the visual improvement. The underlying transformation is identical: a parse step, a tree construction step, and a re-emit step with depth-based indentation. Use whichever term matches your audience; the FixTools prettifier produces output indistinguishable from any reputable beautifier given the same input and settings.

Sensible defaults remove cognitive load. Every configuration option you expose requires the user to evaluate it, even if briefly, before they can use the tool. For a utility that gets invoked many times a day, this evaluation cost adds up. By choosing the right default for the common case, the tool stays useful in the common case while still allowing the rare exception to be handled when needed. Configuration is friction for everyone except the small minority who genuinely need it; defaults serve the majority of users at the moment they need the tool most.

No. The prettifier only adds whitespace and indentation; it does not change any tag, attribute, or text content. A browser rendering the prettified output produces a visual result identical to the original input. This is true even for whitespace-sensitive contexts such as the pre element, because the parser correctly identifies which elements preserve whitespace and treats their content as opaque text rather than reformatting it.

Yes. The prettifier handles complete documents including doctype, html, head, and body elements, and it handles fragments such as a single div or a list of li elements. The same code path serves both, so there is nothing to configure based on the input shape. Paste whatever you have and the prettifier handles it. If you paste a fragment that is missing required parent elements, the parser still produces a sensible tree and the output preserves the fragment structure rather than wrapping it in a synthetic document.

Yes. The prettifier runs entirely in your browser using JavaScript that is loaded with the page. Once the page is open, formatting works without any further network activity. If your connection drops, the tool keeps working as long as the browser tab remains open. This makes it usable in environments where network access is intermittent, such as during travel or on networks with restrictive firewalls that block external services but allow already-loaded pages to continue working normally.