Validation is crucial in controlling the quality of CSL styles and locales. Only styles and locales that are valid XML and conform to the CSL schema can be expected to work correctly with all CSL-compatible applications.
Our first recommendation is our own CSL Validator. Select the version of the CSL schema you wish to validate against, and select the file to validate. Styles and locales can be selected via URL, file upload, or copy and paste into a text field.
CSL styles and locale files can also be validated at http://simonster.github.io/csl-validator.js/. Just paste in your style or locale and click the "Validate" button to validate against the CSL 1.0.1 schema. If there aren't any validation errors you will get the message "Validation successful.".
You can also use Validator.nu:
You can validate your style/locale with any tool that offers XML validation and supports the RELAX NG Compact schema language. Examples are the editors Emacs (when used with the nXML addon) and the commercial oXygen XML Editor (both offer real-time validation), and the command-line utilities Jing and RNV.