HEATKEYS

A web-based XML validator. Can be used for free. Validates XML files, prompts the user for referenced files (e. g., XSD), shows good error messages.

HTML XHTML CSS JavaScript XML XSL ASP SQL ADO VBScript Tutorials References Examples

Free cross-platform web-based Online XML Editor, runs on Linux, Windows, Mac, FireFox, Chrome, IE. Edit XML schema or document. No user registration required.

Code Beautify hepls to edit, minify,beautify,export web code like CSS,HTML,JSON,XML,RSS,XMLtoJSON,JSONtoXML,CSVtoJSON,CSVtoXML,XMLtoCSV,JSONtoCSV convter, viewer,beautify and minifier,editor and Create robots.txt,sitemap

Online tools for developers, including formatters (JSON, XML, HTML, SQL, etc.), minifiers (JavaScript, CSS), validators, compactors and many more!

SourceForge.net. Fast, secure and free downloads from the largest Open Source applications and software directory

W3C

Altova XMLSpy XML editor, plus other leading XML, data management, UML, and Web services software tools for application, web site, and database development, data conversion, and more.

oXygen XML Editor is a cross platform XML Editor providing tools for XML authoring, XML conversion, XSL, XSLT, XQuery, XML Schema, DTD, Relax NG and Schematron development, SOAP and WSDL.

Oracle Documentation