beautifulsoup4
HTML and XML parsing library for Python — parses malformed HTML gracefully and provides Pythonic navigation, search, and modification of parse trees. beautifulsoup4 features: BeautifulSoup(html, parser) with html.parser/lxml/html5lib backends, find()/find_all() with tag name/class/id/attributes, CSS selectors via .select()/.select_one(), .text/.get_text() for content extraction, .attrs dict for attributes, .parent/.children/.next_sibling navigation, Tag.get() for safe attribute access, SoupStrainer for partial parsing, and tree modification (Tag.decompose/extract/insert). Works on broken/real-world HTML that standard parsers reject.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
HTML parsing library. Parses untrusted HTML safely — does not execute scripts. Do not use BS4 output directly as HTML without sanitization (XSS risk). bs4 does not validate URLs — sanitize href/src attributes from untrusted HTML before use.
⚡ Reliability
Best When
Quick HTML scraping from static pages or preprocessing requests/httpx responses — beautifulsoup4 is the easiest way to extract data from HTML with forgiving malformed markup handling.
Avoid When
JavaScript-heavy pages (use playwright), XPath needed (use lxml/parsel), high-performance bulk parsing (use lxml directly), or XML namespaces (use lxml).
Use Cases
- • Agent HTML parsing — from bs4 import BeautifulSoup; soup = BeautifulSoup(html_content, 'html.parser'); title = soup.find('h1').get_text(strip=True); links = [a['href'] for a in soup.find_all('a', href=True)] — basic parsing; agent extracts data from HTML; 'html.parser' is stdlib parser; lxml is faster
- • Agent CSS selector extraction — soup = BeautifulSoup(html, 'lxml'); items = soup.select('.product-card'); for item in items: name = item.select_one('.name').get_text(); price = item.select_one('.price::text') — CSS selectors; agent uses familiar CSS selectors; select() returns list; select_one() returns first or None
- • Agent attribute extraction — soup = BeautifulSoup(html, 'html.parser'); for img in soup.find_all('img'): src = img.get('src', ''); alt = img.get('alt', ''); if src: images.append({'src': src, 'alt': alt}) — attribute access; agent extracts tag attributes safely via .get() with default
- • Agent structured table parsing — table = soup.find('table', class_='data'); headers = [th.get_text(strip=True) for th in table.find_all('th')]; rows = [[td.get_text(strip=True) for td in tr.find_all('td')] for tr in table.find_all('tr')[1:]] — table extraction; agent converts HTML tables to structured data
- • Agent combine with requests — import requests; from bs4 import BeautifulSoup; resp = requests.get(url, headers={'User-Agent': 'Mozilla/5.0'}); soup = BeautifulSoup(resp.content, 'lxml'); data = soup.select('.item') — web scraping pipeline; agent fetches and parses in two steps; use resp.content (bytes) not text for encoding handling
Not For
- • JavaScript-rendered pages — BS4 parses static HTML; for dynamic/JS content use playwright or selenium first, then BS4 on the HTML
- • XPath queries — BS4 does not support XPath; for XPath use lxml directly or parsel
- • High-performance parsing — BS4 is slower than lxml direct API; for maximum speed use lxml.etree directly
Interface
Authentication
No auth — HTML parsing library.
Pricing
beautifulsoup4 is MIT licensed. Free for all use.
Agent Metadata
Known Gotchas
- ⚠ Always specify parser explicitly — BeautifulSoup(html) without parser argument shows GuessedAtParserWarning and may behave differently across environments; always use: BeautifulSoup(html, 'html.parser') or 'lxml' or 'html5lib'; agent code: set parser explicitly; use 'lxml' for speed (pip install lxml); 'html.parser' for zero extra deps
- ⚠ find() returns None not exception — soup.find('div', class_='missing') returns None if not found; calling .text on None raises AttributeError; agent code: always check: elem = soup.find('h1'); if elem: title = elem.get_text(); or use: title = soup.find('h1') and soup.find('h1').get_text() or ''
- ⚠ Tag.text vs Tag.get_text() — .text is shorthand for .get_text(); .get_text(strip=True) removes leading/trailing whitespace; .get_text(separator=' ') joins text nodes with separator; agent code: prefer .get_text(strip=True) for clean extraction; .text may include unexpected whitespace from nested tags
- ⚠ select() uses CSS selectors with limited pseudoclass support — BS4 CSS support: basic selectors (.class, #id, tag, [attr]), combinators (descendant space, child >, adjacent +), and some attribute selectors; no :nth-child(n), :first-of-type pseudo-elements; agent code needing complex CSS: check BS4 docs for supported selectors; parsel (Scrapy's selector) has better CSS/XPath
- ⚠ import is bs4 not beautifulsoup4 — pip install beautifulsoup4; from bs4 import BeautifulSoup (underscore not hyphen, bs4 not beautifulsoup4); agent requirements.txt: beautifulsoup4>=4.12; import: from bs4 import BeautifulSoup, Tag, NavigableString; common mistake: import beautifulsoup4 (fails)
- ⚠ Parser behavior differs for malformed HTML — html.parser and lxml fix broken HTML differently; soup.find('p') inside unclosed tags may give different results with different parsers; agent code scraping real-world HTML: test parser choice against actual target HTML; lxml is most forgiving and fastest; html5lib most spec-compliant
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Scores are editorial opinions as of 2026-03-07.