Zerdly

HTML Encoder / Decoder

Encodes and decodes HTML entities, escaping and unescaping special characters.

100% FreeRuns in your browserBasic
How to use this calculator

Input

Direction

0 characters · 0 bytes (UTF-8)

Shortcut: Alt+Shift+S switches direction.

Output

Enter text to see the result.

Runs entirely in your browser. Your input is not uploaded or stored.

How the method works

Raw text and protected preview are separate outputs
Illustrative method
Raw text and protected preview are separate outputsFlow: input text or file, parsed locally in an inert document, converted, then split into two outputs — the raw converted text for copy or download, and a sanitised preview shown in a sandbox with no network access.Input text or filestays on your deviceParse locallyno scripts, no fetchConvertescape · map structureRaw output textcopy or downloadSanitise → previewsandboxed, no networkexport deliberately
Parse locally (nothing is fetched or run) → convert → two separate outputs: the raw text you copy or download as written, and a sanitised preview in a sandboxed frame with scripts and network blocked. Downloading is always a deliberate click.

Encoding escapes text for one HTML context; it is not a sanitiser, and decoding runs exactly once per action. Fixed example values for illustration — not your result.

How to use this calculator

  1. Choose Encode or Decode. For encoding, pick the context: element text, or a quoted attribute value.
  2. Paste your text. The output updates as you type, with character and byte counts.
  3. Copy or download the result; every escaped or decoded part is highlighted. To decode a second layer, switch direction deliberately — the button or Alt+Shift+S makes the output the new input.

How it works

Text mode escapes &, < and >; attribute mode also escapes " and '. Named (&amp;) or numeric (&#38;) references are your choice, and existing entities can be kept rather than double-encoded.

Decoding runs once, through the browser's own HTML parser in an inert document, so every named and numeric reference follows the HTML standard — and the result is only ever shown as text.

Escaping protects one context; it is not sanitising a whole HTML document, and event attributes, JavaScript, CSS and URLs each need their own handling.

Worked example

A&B< and &amp;lt;. Encoding A&B< gives A&amp;B&lt;. Decoding &amp;lt; once gives &lt; — not <, because it was encoded twice.

Common mistakes

  • Using text-mode escaping inside an attribute (quotes must be escaped there).
  • Decoding repeatedly until nothing changes, which can turn data back into markup.
  • Treating escaped text as a sanitised HTML document.

Tips

  • Runs entirely in your browser. Your input is not uploaded or stored.

Frequently asked questions

When do I need this?

To show literal HTML or code on a page, or to read entity-encoded text.

Privacy?

Runs entirely in your browser. Your input is not uploaded or stored.

Related tools

Explore more in PDF, Image, File, Data & Developer Tools.

Cite this tool

Zerdly. (2026). HTML Encoder / Decoder. Retrieved from https://www.zerdly.com/tools/html-encoder-decoder/

Tip: Enter any known values to calculate the remaining results.

Designed to run locally in your browser. Tool inputs are not intentionally stored by Zerdly unless stated otherwise.