HTML Entity Encoder

What does the HTML Entity Encoder do?

The HTML Entity Encoder converts reserved markup characters (<, >, &, ", ', `, =) and non-alphanumeric unicode symbols into safe HTML entity codes (<, >, &, ', <). It supports Named Entities, Decimal Numeric Entities, and Hexadecimal Unicode point formats to prevent Cross-Site Scripting (XSS).

Core Concepts

Understanding HTML entity encoding formats:

• Named Entities: Replaces reserved characters with readable W3C mnemonic names (e.g. < for <, > for >, & for &, " for ").
• Decimal Numeric Entities: Formats characters into their decimal ASCII code points (e.g. < for <, > for >).
• Hexadecimal Entities: Encodes characters using their hexadecimal byte representation (e.g. < for <, > for >).
• Full Non-Alphanumeric Mode: Encodes all punctuation, whitespace, and special unicode symbols for strict sanitization.

How to use the tool?

1. Enter Raw HTML: Paste your raw HTML markup or user-submitted text into the editor or click Load Sample.
2. Select Entity Format: Choose Named Entities, Decimal Numeric Entities, or Hexadecimal Entities, and optionally toggle Encode all non-alphanumeric characters.
3. Encode & Copy: Click Encode HTML Entities, then click Copy or Download to export the XSS-safe markup.

Related Developer Utilities

If you work with HTML entities, security sanitization, and markup formatting, explore these complementary tools:

• HTML Entity Decoder: Convert HTML entities back to raw unescaped text.
• HTML Formatter & Beautifier: Format and indent unescaped HTML documents.
• HTML Syntax Validator: Validate HTML syntax and inspect tag nesting errors.
• HTML Tag Stripper: Strip all HTML tags and extract clean plain text.

REST API Integration

Blueutils provides a free REST API endpoint (POST https://blueutils.com/api/html/html-encoder) to programmatically convert reserved HTML markup characters into named, decimal, or hexadecimal HTML entities.

API Request Parameters

API Request Payload Examples

cURL

curl -X POST https://blueutils.com/api/html/html-encoder \
  -H "Content-Type: application/json" \
  -d '{
    "rawText": "<div class=\"card\">Hello & World</div>",
    "options": { "mode": "named", "encodeAll": false }
  }'

Python

import requests

url = "https://blueutils.com/api/html/html-encoder"
payload = {
    "rawText": "<div class=\"card\">Hello & World</div>",
    "options": { "mode": "named", "encodeAll": False }
}
headers = {"Content-Type": "application/json"}
response = requests.post(url, json=payload, headers=headers)
print(response.json())

Java

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;

public class Main {
    public static void main(String[] args) throws Exception {
        String jsonPayload = """
            {
                "rawText": "<div class=\\"card\\">Hello & World</div>",
                "options": { "mode": "named", "encodeAll": false }
            }
            """;

        HttpClient client = HttpClient.newHttpClient();
        HttpRequest request = HttpRequest.newBuilder()
            .uri(URI.create("https://blueutils.com/api/html/html-encoder"))
            .header("Content-Type", "application/json")
            .POST(HttpRequest.BodyPublishers.ofString(jsonPayload))
            .build();

        HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());
        System.out.println(response.body());
    }
}

API Response Parameters

API Response Payload Examples

Success Response (HTTP 200 OK)

{
  "isValid": true,
  "mode": "named",
  "encodeAll": false,
  "entityCount": 4,
  "encodedText": "<div class="card">Hello & World</div>",
  "output": "<div class="card">Hello & World</div>"
}

Validation Failure Response (HTTP 400 Bad Request)

{
  "isValid": false,
  "error": "Invalid input: Text payload to HTML encode cannot be empty."
}

Rate Limit Exceeded Response (HTTP 429 Too Many Requests)

{
  "error": "API rate limit exceeded. Please wait or contact support@blueutils.com."
}

Why use an API to encode HTML entities?

Integrating the HTML Entity Encoder API into backend template engines, CMS publish pipelines, or AI agent tool calling provides key benefits:

• Rapid Script Validation: Escapes untrusted user input before storing in databases or rendering dynamic HTML emails to prevent XSS injection.
• Optimized Token Efficiency for AI Agents: LLMs frequently mix named and numeric entities inconsistently. Calling the API encodes characters deterministically without consuming token budget.
• Deterministic Accuracy Without Hallucinations: Ensures 100% compliant W3C character entity substitution.

Native Usage

How to encode HTML entities locally in terminal environments or scripts:

Windows (CMD / PowerShell)

# Encode HTML entities in PowerShell
[System.Net.WebUtility]::HtmlEncode('<div class="card">Hello & World</div>')

Linux / Unix (Bash)

# Encode HTML entities using Python in Linux
python3 -c "import html; print(html.escape('<div class=\"card\">Hello & World</div>', quote=True))"

Python

Using Python html.escape:

import html

raw_text = '<div class="card">Hello & World</div>'
encoded = html.escape(raw_text, quote=True)
print("Encoded:", encoded)

Java

Using Java String.replace:

public class HtmlEncoderExample {
    public static void main(String[] args) {
        String raw = "<div class=\"card\">Hello & World</div>";
        String encoded = raw.replace("&", "&amp;")
                            .replace("<", "&lt;")
                            .replace(">", "&gt;")
                            .replace("\"", "&quot;")
                            .replace("'", "&#39;");
        System.out.println(encoded);
    }
}