Altova XMLSpy includes a powerful XSLT editor that includes:

- Support for XSLT 1.0, 2.0, and 3.x
- Process XSLT against XML or JSON
- XSLT editor with syntax coloring, source folding, etc.
- Code completion, context-sensitive entry helpers
- XSLT validation & troubleshooting
- Interactive XPath builder, tester, and debugger
- XSL Outline window
- Integrated web browser
- XSLT back-mapping
- XSLT debugger
- XSL Speed Optimizer

