I once pasted a real API response into an online JSON formatter to debug a bug at 1am, then remembered it had a live JWT in it
Nothing happened that time, but I never found out where that formatter's server actually sent my paste, or how long it kept it. That's the moment I stopped trusting "free online JSON formatter" tools by default, and it's a big part of why SolveBar's JSON Formatter runs on JSON.parse() and JSON.stringify() directly in your browser, with zero network calls in the formatting path.
XML ruled data exchange for the SOAP era — strictly typed, verbose, and it powered a lot of the early API web. JSON has mostly replaced it since, for a concrete reason: every tag in XML gets written twice. <name>John</name> spends 17 characters saying "name" twice; "name": "John" says it once in 15. That gap compounds across a real payload with 50+ fields, and JSON is also a subset of JavaScript — native JSON.parse() has shipped in every browser since ECMAScript 5 in 2009, so there's no recursive DOM parser to run, which means less main-thread work and matters for responsiveness metrics like Interaction to Next Paint.
Where JSON actually wins
| Feature | JSON | XML |
|---|---|---|
| Readability | Flat key-value pairs | Nested opening/closing tags |
| Parsing | Native via JSON.parse() | Needs a DOM parser |
| Payload size | Smaller — no repeated tag names | Larger — every tag written twice |
| Data types | Arrays, numbers, booleans, objects | Everything is a string unless you add XSD |
The part that actually worries me: where your paste goes
A lot of "online JSON formatters" run the actual parsing on a server — you paste, it POSTs to a backend, the backend formats it and sends it back. If what you pasted contains a live JWT, an API key, or a customer record, that secret just left your machine and landed in a stranger's server logs, possibly indefinitely. You'd never know from the UI; the formatted output looks identical either way.
SolveBar's formatter never does that round trip. Paste JSON, hit format, and the only code that ever touches it is JSON.parse() followed by JSON.stringify(parsed, null, spaces) — both run in your tab, both work with your network connection off. Open DevTools, watch the Network tab, format a payload with a fake secret in it, and you'll see exactly 0 outbound requests.
When XML is still the right answer
JSON winning the API war doesn't mean XML is dead. It's still the better fit for 3 real cases: document formats with rich embedded metadata (Microsoft Word's .docx is XML under the hood), legacy banking and finance systems still running WSDL/SOAP integrations from the 2000s that would cost more to replace than to keep, and situations needing strict schema validation that JSON Schema doesn't fully match yet.
For the other 90%+ of REST APIs shipped in 2026, JSON is the default for a real reason — smaller payloads, native parsing, easier debugging. Just don't hand your API keys to a server you don't control while you're formatting them. Use SolveBar's JSON Formatter or the XML Beautifier if you still need the older format.