How to Format XML

XML never died — it just moved into the plumbing. SOAP payloads, RSS feeds, sitemaps, Android layouts, Maven builds, invoice standards: all XML, and nearly all of it arrives as an unreadable single line. Formatting it is easy; formatting it safely requires knowing which whitespace is decoration and which is data.

What a pretty-printer does

Good XML formatting follows a few conventions:

• One element per line, children indented one level deeper
• Elements with a single text value stay on one line: <title>Clean Code</title>
• Empty elements collapse to self-closing form: <br/>
• Attributes stay on the opening tag; comments and CDATA are preserved

Two or four spaces per level is convention; deeper matters less than consistency.

The whitespace rule that keeps you safe

Whitespace between elements is structural and safe to reflow. Whitespace inside text content is real data — reformatting <name>Ada Lovelace</name> must not touch the space in the name. Documents with mixed content (text and tags interleaved, like HTML paragraphs) are the risky case: aggressive reformatting can change meaning, which is why careful formatters leave single-text elements inline.

Validate first, format second

A formatter that doesn't parse can't warn you. Real parsing catches the classic XML errors before they reach production:

• Mismatched or unclosed tags (<a><b></a>)
• Unescaped special characters — a bare & is the all-time champion
• Multiple root elements, or stray text outside the root
• Unquoted attribute values

Remember the five entities: & < > " '. Everything else can be literal (in UTF-8) or numeric references.

When to minify instead

The reverse operation — stripping inter-element whitespace — matters for payloads sent over the wire and for large feeds where indentation can add 20–30% of file size. Beautify for humans reading; minify for machines transferring. Both directions must preserve the actual data exactly.

XML vs JSON vs YAML, in one breath

JSON won APIs with less syntax; YAML won config files with even less; XML keeps the territories where attributes, namespaces, schemas and document-style mixed content earn their verbosity — publishing, enterprise integration, office formats. Odds are you touch all three weekly.

Format yours now

The XML formatter validates with a real parser (clear error messages included), beautifies with your chosen indent or minifies, and preserves namespaces, comments and CDATA — entirely in your browser, so enterprise payloads stay private. For the sibling formats, see the JSON formatter and the YAML ↔ JSON converter.