Online HTML Editor - Free Editor With Highlighting

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About This HTML Editor

HTML is a markup language, not a programming language: it describes what content is, and leaves how it looks to CSS and how it behaves to JavaScript. That separation is the whole design, and most bad HTML comes from ignoring it - using a div where a button belongs, or a table for layout.

The editor highlights tags and attributes, matches opening and closing tags, and indents nested structure so you can see where an element actually ends.

Semantic elements and what they mean

HTML syntax reference
Syntax	What it does
`<header> <footer>`	Introductory and closing content for the page or for the nearest sectioning element.
`<nav>`	A block of major navigation links. Not every group of links needs one.
`<main>`	The dominant content of the page. Exactly one per document, and never nested inside an article or aside.
`<article>`	Self-contained content that would still make sense syndicated elsewhere.
`<section>`	A thematic grouping, normally with a heading. If it has no heading, it is probably a div.
`<aside>`	Content tangentially related to the surrounding content - a sidebar, a pull quote.
`<figure> <figcaption>`	An image, diagram or code block with its caption bound to it.
`<button> vs <a>`	A button performs an action; a link navigates somewhere. Getting this wrong breaks keyboard and screen reader behaviour.

Mistakes that cost you accessibility and rankings

Void elements. <br>, <img>, <input>, <meta> and <link> have no closing tag. Writing </br> is not valid HTML.
Heading order. One h1 per page, and never skip a level to get a smaller font - that is what CSS is for. Screen reader users navigate by heading structure.
alt text. Every <img> needs an alt attribute. Decorative images take alt="", which is different from omitting it.
Labels. Every form control needs a <label> whose for matches the input's id. A placeholder is not a label - it disappears the moment someone types.
Attribute quoting. Unquoted attribute values break silently on any value containing a space.

Your Code Never Leaves Your Browser

The editor is JavaScript running in this tab. Nothing you type is posted to a server, stored, logged or associated with you, and there is no account and no autosave. That makes it safe to paste a snippet from a private codebase in order to read it with highlighting. The trade-off is that nothing persists either — refresh the page and your content is gone, so copy anything you want to keep.

Frequently Asked Questions

Does the editor validate my HTML?

It highlights and matches tags, which catches most structural mistakes as you type, but it is not a validator. For a conformance check, run your markup through the W3C validator.

Do semantic tags actually affect SEO?

Indirectly and modestly. Search engines use structure to work out what the main content of a page is, and semantic elements make that unambiguous. The larger benefit is accessibility: landmarks are how screen reader users skip straight to the content.

Should I close every tag?

HTML5 allows some closing tags to be omitted, but writing them all makes the document unambiguous for humans and for parsers. Void elements are the exception - they take no closing tag at all.