Extract Content Between HTML Tags Regex

Extract text content between matching HTML opening and closing tags using regex with lookbehind and lookahead assertions.

Pattern Breakdown

(?<=<(\w+)>).*(?=<\/\1>)

Components

Detailed Breakdown

• (?<=<(\w+)>) - Positive lookbehind:
  • (?<=...) - Lookbehind assertion (not included in match)
  • <(\w+)> - Opening tag with captured tag name
• .* - Matches any content (greedy, matches as much as possible)
• (?=<\/\1>) - Positive lookahead:
  • (?=...) - Lookahead assertion (not included in match)
  • <\/\1> - Closing tag using backreference

Examples

Matches:

• Input: <div>Hello World</div> → Matches: Hello World
• Input: <p>This is a paragraph</p> → Matches: This is a paragraph
• Input: <span class="test">Content here</span> → Matches: Content here
• Input: <h1>Title</h1> → Matches: Title

Doesn't Match:

• <div>content</span> (mismatched tags)
• <div>content (no closing tag)
• content</div> (no opening tag)
• <div><span>nested</span></div> (only matches inner content if pattern matches span)

Implementation

JavaScript

// Note: JavaScript doesn't support lookbehind with variable length
// Use alternative approach with capturing groups
const extractContentRegex = /<(\w+)>(.*?)<\/\1>/;
const match = '<div>Hello World</div>'.match(extractContentRegex);
if (match) {
  console.log(match[2]); // "Hello World"
}

// For environments supporting lookbehind (ES2018+)
const extractRegex = /(?<=<(\w+)>).*(?=<\/\1>)/;
const result = '<div>Hello World</div>'.match(extractRegex);

Python

import re
extract_regex = r'(?<=<(\w+)>).*(?=<\/\1>)'
match = re.search(extract_regex, '<div>Hello World</div>')
if match:
    print(match.group(0))  # "Hello World"

# Alternative with capturing groups
extract_alt = r'<(\w+)>(.*?)<\/\1>'
match = re.search(extract_alt, '<div>Hello World</div>')
if match:
    print(match.group(2))  # "Hello World"

Go

import "regexp"

// Go supports lookahead but lookbehind support is limited
// Use capturing groups instead
extractRegex := regexp.MustCompile(`<(\w+)>(.*?)</\1>`)
match := extractRegex.FindStringSubmatch("<div>Hello World</div>")
if len(match) > 2 {
    content := match[2] // "Hello World"
}

Limitations

1. Lookbehind support: Not all regex engines support variable-length lookbehind
2. Greedy matching: .* is greedy and may match too much with nested tags
3. No nested tags: Doesn't properly handle nested HTML structures
4. No attributes: Doesn't account for attributes in opening tags
5. Single match: Only matches first occurrence (use global flag for all)
6. No whitespace handling: Doesn't trim whitespace automatically

When to Use

• Extracting content from simple HTML tags
• When you know the tag structure
• Quick content extraction
• Simple HTML parsing tasks
• When tags are not nested

For production, consider:

• Using HTML parsers (DOMParser, BeautifulSoup, etc.)
• Using non-greedy quantifier .*? for better matching
• Handling nested tags properly
• Supporting attributes in opening tags
• Using proper HTML parsing libraries