To match open HTML tags but exclude self-closing XHTML tags using Regular Expressions (RegEx), you can use the following pattern:

RegEx Pattern

<([a-zA-Z][a-zA-Z0-9]*)(?![^>]*\/>)>

Explanation of the Pattern

1. <: Matches the opening < of an HTML tag.
2. ([a-zA-Z][a-zA-Z0-9]*): Captures the tag name, which starts with a letter and can contain letters and numbers.
   • [a-zA-Z]: Ensures the tag starts with a letter.
   • [a-zA-Z0-9]*: Allows for additional alphanumeric characters.
3. (?![^>]*\/>): Negative lookahead to exclude tags containing / before the closing > (self-closing tags).
   • [^>]*: Matches any characters except > (ensures we’re still inside the tag).
   • \/>: Looks for the self-closing />.
4. >: Matches the closing > of the opening tag.

---

Example HTML Snippet

<div>
  <img src="image.jpg" />
  <input type="text" />
  <span>Text</span>
  <br />
  <p>Paragraph</p>
</div>

---

Matches

Using the RegEx <([a-zA-Z][a-zA-Z0-9]*)(?![^>]*\/>)>:

1. Matches:
   • <div>
   • <span>
   • <p>
2. Excludes:
   • <img src="image.jpg" />
   • <input type="text" />
   • <br />

---

Code Example

JavaScript Example

const html = `
<div>
  <img src="image.jpg" />
  <input type="text" />
  <span>Text</span>
  <br />
  <p>Paragraph</p>
</div>
`;

const regex = /<([a-zA-Z][a-zA-Z0-9]*)(?![^>]*\/>)>/g;
const matches = html.match(regex);

console.log(matches);
// Output: [ '<div>', '<span>', '<p>' ]

---

Python Example

import re

html = '''
<div>
  <img src="image.jpg" />
  <input type="text" />
  <span>Text</span>
  <br />
  <p>Paragraph</p>
</div>
'''

regex = r'<([a-zA-Z][a-zA-Z0-9]*)(?![^>]*\/>)>'
matches = re.findall(regex, html)

print(matches)
# Output: ['div', 'span', 'p']

---

Notes

• This pattern does not account for malformed HTML.
• It assumes tags are properly closed or self-closed.
• It doesn’t distinguish between <tag> and <tag attr="value">. Both are matched as long as they are not self-closing.