HTML Encoder / Decoder

An HTML Encoder and Decoder converts special HTML characters into their corresponding HTML entities. When text containing characters like angle brackets, ampersands, and quotation marks needs to be displayed in a web page, these characters must be escaped to prevent them from being interpreted as HTML code. A user-submitted comment containing the text DO NOT use the less than symbol in HTML would break the page if the angle bracket was not encoded.

HTML encoding replaces special characters with their entity references. The less-than symbol becomes less-than semicolon. The greater-than symbol becomes greater-than semicolon. The ampersand becomes ampersand semicolon. Double quotes become quotation semicolon. These entities ensure the browser displays the intended character rather than interpreting it as HTML markup.

Web developers use HTML encoding whenever user-generated content is displayed on a website. Comments, forum posts, user profiles, and any other content that originates from users must be HTML-encoded before display to prevent cross-site scripting attacks. XSS attacks work by injecting malicious script tags into content that the browser then executes. Proper HTML encoding neutralizes these injection attempts by converting the injection characters into harmless entities.

Content management system users need HTML encoding when pasting code snippets into their content. A blog post that includes a JavaScript code sample with angle brackets and quotes would break the page layout if the HTML characters were not encoded. Using an HTML encoder ensures that the code sample displays correctly as text rather than being parsed as HTML.

Email developers encode HTML special characters in email templates to ensure consistent rendering across email clients. An ampersand in a URL parameter within an email link must be encoded as the HTML entity to prevent parsing errors in older email clients that have limited HTML parsing capabilities.

Database administrators encoding data before inserting it into web-facing fields use HTML encoding as a defense-in-depth measure. Even if application-level encoding fails, database-level encoding provides an additional layer of protection against stored XSS attacks.

The decoder converts HTML entities back to their raw character equivalents. This is useful when extracting text from HTML sources where the content has been entity-encoded. Decoding the entities reveals the original text including the special characters that were encoded for safe HTML display.

The tool supports all standard HTML entities including the five XML-essential entities and named entities for accented characters, symbols, and punctuation marks. Unicode characters that do not have named entities can be encoded using numeric character references in either decimal or hexadecimal format.