XML Validator
Checks that an XML document is well formed and says which tag broke it.
Results
What this tool does
The commonest XML failure is a tag that never closes, and the second commonest is tags that close in the wrong order. Neither is visible when the document is one long line. This walks the whole thing keeping a stack of what is open, and when a closing tag does not match what is on top it says both names — the one it expected and the one it found — which is usually enough to spot the mistake immediately.
Formula
checks that every tag opened is closed, and in the right order
Variables
| Symbol | Meaning | Unit |
|---|---|---|
text | XML | — |
VD | Verdict | — |
TG | Tags | — |
DP | Nesting depth | — |
SB | Size before | B |
Worked example
- XML<catalogo><livro id="1"><titulo>Os Maias</titulo></livro></catalogo>
- Verdictvalid
- Tags3
- Nesting depth3
- Size before68 B
Limitations
- The calculation runs entirely in your browser. The values you type are never sent to a server.
Frequently asked questions
Is well formed the same as valid?
No, and the distinction matters. Well formed means the syntax is right: every tag closes, they nest in the correct order, attributes are quoted. Valid means the document also obeys a schema — a DTD, an XSD — that says which elements may appear where and what they must contain. This checks well-formedness, which is the part that fails ninety-nine times out of a hundred. Checking against a schema needs the schema, and that is a different job.