XML Viewer and Formatter

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check if xml is well formed

Check whether XML is well-formed (with the error line and column)

Paste the XML into the box and the check runs at once: if it is correct the banner turns green; if not, it gives the line, the column and the reason, with the source excerpt and a ^ marking the exact spot.

The rules that make an XML well-formed

A well-formed XML meets the syntax rules of XML 1.0. There is exactly one root element, and nothing but comments, instructions and whitespace sits outside it. Every opened tag is closed, in the reverse order of opening. Attributes have quoted values, do not repeat on the same element and do not contain the less-than sign. Names start with a letter, underscore or colon. An & may only appear as a reference (&, <, >, ", ' or a numeric one such as é). Comments cannot hold two hyphens in a row, and control characters such as code 1 are forbidden. The <?xml ...?> declaration, if present, must be the very first thing in the file.
The analysis stops at the first error, as the specification requires, and reports its position. For a closing tag that does not match, the report also gives the line where the element was opened, which is almost always where the fix starts. The same rules apply to any system that reads XML, so fixing it here avoids the vague message many importers return. Two concepts are worth keeping apart: well-formed is syntax, while valid means obeying a schema (XSD or DTD). This page checks the first; an XML can be well-formed and still be rejected by a schema.
Namespace prefixes with no xmlns declaration, such as soap:Body outside an Envelope that declares soap, are not an XML 1.0 error but do break the namespaces recommendation; the tool accepts the document and shows a warning. A DOCTYPE with entities is read without expanding anything, which protects against hostile files. The limits of 15 MB, 1,000,000 nodes and 512 levels keep a gigantic or deeply nested file from freezing the browser.

Common errors and where they show up

Closing tag out of order

Input: <a></a>
Expected output: linha 1, coluna 7: fechamento </a> não casa com

Column 7 is where </a> begins.

Repeated attribute

Input: <a x="1" x="2"/>
Expected output: linha 1, coluna 10: atributo x duplicado

The second occurrence is the one flagged.

Stray ampersand

Input: <a>R&D</a>
Expected output: linha 1, coluna 5: referência inválida

Write R&D to fix it.

Unquoted attribute value

Input: <a x=1/>
Expected output: linha 1, coluna 6: valor precisa de aspas

Use x="1".

Two root elements

Input: <a/>
Expected output: linha 1, coluna 5: conteúdo depois da raiz

Wrap both in a parent element.

Full tool FAQ

How do I open an XML file?

Drop the file on the upload area or pick it with the button. The tool detects the encoding (UTF-8, UTF-16 or the one declared in the header, such as ISO-8859-1), shows the formatted text and builds the tree. You can also paste the content. Any text editor or browser can open XML, but only here do you get formatting, a tree, search and NF-e reading in one place with nothing to install.

What does malformed XML mean and how is the error pointed out?

What is the difference between well-formed and valid XML?

Is my file uploaded to a server?

How do I read the XML of a Brazilian electronic invoice (NF-e)?

Does the NF-e reading work for NFC-e, CT-e and MDF-e?

Does formatting or minifying change the XML content?

Is it safe to open XML from an unknown source here?

What is the maximum file size?

How do I use XPath in the search?

Frequently asked questions

What is a well-formed XML?

One that follows the XML syntax rules: a single root element, tags closed in the right order, quoted attributes and references written correctly.

Does well-formed mean valid?

No. Valid also requires obeying a schema such as XSD or DTD. The tool checks well-formedness only, which is the prerequisite for any schema validation.

Why does only one error appear at a time?

Because in the XML specification a well-formedness error is fatal: after it the rest of the text cannot be interpreted safely. Fix the first one and the check moves on to the next.

Next steps

The rules that make an XML well-formed

A well-formed XML meets the syntax rules of XML 1.0. There is exactly one root element, and nothing but comments, instructions and whitespace sits outside it. Every opened tag is closed, in the reverse order of opening. Attributes have quoted values, do not repeat on the same element and do not contain the less-than sign. Names start with a letter, underscore or colon. An & may only appear as a reference (&, <, >, ", ' or a numeric one such as é). Comments cannot hold two hyphens in a row, and control characters such as code 1 are forbidden. The <?xml ...?> declaration, if present, must be the very first thing in the file.

The analysis stops at the first error, as the specification requires, and reports its position. For a closing tag that does not match, the report also gives the line where the element was opened, which is almost always where the fix starts. The same rules apply to any system that reads XML, so fixing it here avoids the vague message many importers return. Two concepts are worth keeping apart: well-formed is syntax, while valid means obeying a schema (XSD or DTD). This page checks the first; an XML can be well-formed and still be rejected by a schema.

Namespace prefixes with no xmlns declaration, such as soap:Body outside an Envelope that declares soap, are not an XML 1.0 error but do break the namespaces recommendation; the tool accepts the document and shows a warning. A DOCTYPE with entities is read without expanding anything, which protects against hostile files. The limits of 15 MB, 1,000,000 nodes and 512 levels keep a gigantic or deeply nested file from freezing the browser.

Common errors and where they show up

Closing tag out of order

Input: <a></a>
Expected output: linha 1, coluna 7: fechamento </a> não casa com

Column 7 is where </a> begins.

Repeated attribute

Input: <a x="1" x="2"/>
Expected output: linha 1, coluna 10: atributo x duplicado

The second occurrence is the one flagged.

Stray ampersand

Input: <a>R&D</a>
Expected output: linha 1, coluna 5: referência inválida

Write R&D to fix it.

Unquoted attribute value

Input: <a x=1/>
Expected output: linha 1, coluna 6: valor precisa de aspas

Use x="1".

Two root elements

Input: <a/>
Expected output: linha 1, coluna 5: conteúdo depois da raiz

Wrap both in a parent element.

Full tool FAQ

How do I open an XML file?

What does malformed XML mean and how is the error pointed out?

What is the difference between well-formed and valid XML?

Is my file uploaded to a server?

How do I read the XML of a Brazilian electronic invoice (NF-e)?

Does the NF-e reading work for NFC-e, CT-e and MDF-e?

Does formatting or minifying change the XML content?

Is it safe to open XML from an unknown source here?

What is the maximum file size?

How do I use XPath in the search?

Frequently asked questions

What is a well-formed XML?

One that follows the XML syntax rules: a single root element, tags closed in the right order, quoted attributes and references written correctly.

Does well-formed mean valid?

No. Valid also requires obeying a schema such as XSD or DTD. The tool checks well-formedness only, which is the prerequisite for any schema validation.

Why does only one error appear at a time?

Because in the XML specification a well-formedness error is fatal: after it the rest of the text cannot be interpreted safely. Fix the first one and the check moves on to the next.