HTML Entity Encoder and Decoder

Convert text to and from named HTML entities without installing a package or relying on a browser DOM. Encode mode protects markup-sensitive characters such as ampersands, angle brackets, quotation marks, and apostrophes, while also handling a practical set of common symbols and typography. Decode mode reverses recognized named entities and rejects unknown names instead of silently preserving a likely mistake.

Encode text before placing it in HTML

Use encode mode when plain text must be represented safely inside HTML source. An ampersand can begin an entity reference, angle brackets can be mistaken for tags, and quotation marks can interfere with surrounding syntax when text is assembled into markup. The converter replaces supported characters with named references such as <code>&amp;amp;</code>, <code>&amp;lt;</code>, <code>&amp;gt;</code>, <code>&amp;quot;</code>, and <code>&amp;apos;</code>.

It also recognizes frequently used currency, legal, mathematical, punctuation, and spacing characters, including copyright, registered trademark, euro, nonbreaking space, dashes, curly quotation marks, bullets, and ellipses. Encoding is performed in one pass so the ampersands introduced by the conversion are not encoded a second time. Ordinary letters, numbers, whitespace, emoji, and unsupported characters remain unchanged.

This behavior makes the result readable while protecting the characters that commonly matter in markup. Remember that entity encoding is a text representation step, not a complete HTML sanitizer: it does not validate a document, remove unsafe tags from existing markup, or decide whether a value is safe for a JavaScript, CSS, or URL context.

Decode named entities with strict validation

Use decode mode when input contains named references and the original characters are needed for display, comparison, indexing, export, or further text processing. Each complete reference shaped like an ampersand, a name, and a semicolon is looked up in the capability’s fixed table. Recognized forms are replaced with their corresponding Unicode characters, preserving every part of the string around them.

Entity names are case-sensitive because differently capitalized names can have different meanings in HTML. Strict rejection is useful in automated pipelines because a misspelling such as <code>&amp;copry;</code> does not quietly pass through and appear as broken text later. Text containing a plain ampersand without an entity-shaped name and semicolon remains unchanged.

This capability focuses deliberately on named entities; decimal and hexadecimal numeric character references are outside this contract. The same fixed mapping is used for every execution, so results do not depend on a browser version, external package, network response, locale, or mutable global data.

Choose the mode and integrate the result

Send two fields: <code>text</code> contains the source string and <code>mode</code> is either <code>encode</code> or <code>decode</code>. Both are required so an integration never guesses which direction was intended. For an encoder workflow, pass human-authored content before embedding it in markup and store or transmit the returned text.

For a decoder workflow, treat an unknown-entity error as a validation failure and correct the producer rather than suppressing it. For large systems, keep the conversion at a clear boundary: encode when entering an HTML representation and decode only when leaving that representation. Repeatedly alternating the modes can obscure ownership of escaping and may encourage accidental double encoding elsewhere in an application.