XML Merge
Combine several documents under one new or shared root element, with an optional source attribute for provenance.
What is XML Merge?
A document combiner. Multiple exports with the same shape are the common case: several API responses, per-region exports or a paginated feed, all of which need to end up as one document a consumer can read.
How it works
Each source is parsed and its root element is imported into the result. In wrapper mode a new root element is created around them and given a namespace if you supply one; in shared mode the first document's root is reused so the result has the same shape as its inputs. A source attribute is added to each merged root with the file name, and duplicate declarations, namespace conflicts and unparseable sources are reported instead of being skipped quietly.
- Paste the document. Drop in XML, a schema, a feed or an XPath expression. Everything is parsed in the page: no upload, no server round trip, and the tools keep working with the network switched off.
- Set the options that match your document. Indent unit, whether to keep comments, which dialect, which output method. The defaults are the safe ones — nothing that changes meaning is enabled for you.
- Read the result, then copy or download it. Results appear as you type, copy straight to the clipboard, and download with a sensible filename (.xml, .xsd, .csv). Reset returns every field to its default.
Examples
A minified document from an API response
Paste one line of XML and the Formatter indents it, wraps long start tags one attribute per line and normalises empty elements — without touching text inside mixed content.
An XPath that works in Chrome and not in your servlet
The XPath Tester evaluates against a real tree and reports the axis or function it cannot support, instead of returning zero nodes and letting you guess why.
A document that will not parse
The Validator gives line and column for every mismatched tag, stray ampersand and duplicate attribute, with the reason in words: which open element was expected, which was found.
A schema that only half matches your data
The XSD Validator marks each violation with the path of the offending node, and the Schema Generator goes the other way — inferring a starting-point XSD from real documents.
Common mistakes
Assuming a pretty-printer cannot change meaning
Whitespace between elements is often insignificant, but inside mixed content it is not: `<p>Hello <b>world</b></p>` must stay on one line. Formatting here re-indents element-only content and leaves mixed content alone.
Treating a validation pass as proof of interoperability
The DTD and XSD validators implement honest subsets. A document reported valid here can still be rejected by a full validator that understands identity constraints, substitution groups or XSD 1.1 assertions — each page lists what it does not cover.
Reading the whole document because the parser did
A DOCTYPE is not inert. If your parser resolves external entities, pasting an untrusted document is enough to read a file or call an internal URL. The XXE Risk Checker shows what a document asks for; the fix is in the parser configuration.
Forgetting that attributes and elements are not interchangeable
`<id>1</id>` and `id="1"` mean different things to every schema and every XPath. When converting to CSV or YAML the distinction is preserved (`@id`), because flattening it away is the change that costs an afternoon later.
Frequently asked questions
Which mode should I use?
Wrapper when the inputs are logical documents and you want a manifest around them; shared when they are pages of one data set and the consumer expects the same root element it would get from a single response. Shared mode loses the top-level attributes of all but the first document, and says so.
What happens if two documents declare the same namespace differently?
The conflict is reported with both URIs. The merge keeps each declaration on the element that used it rather than rewriting it, because silently reassigning a namespace changes the meaning of every element under it.
Can it merge documents with different structures?
It can, but the result is two different shapes under one root, which most consumers cannot handle. That is reported as a warning: merge documents that share a schema, and use the wrapper root so the file names stay attached to their contents.