openrefine.org
OpenRefine is a free, open source tool for working with messy data. It enables users to clean data, transform it between formats, and extend it with web services and external data. All data processing occurs locally on the user's machine rather than in cloud services. Key features include faceting to drill through large datasets, clustering to fix inconsistencies by merging similar values, reconciliation to match datasets to external databases, infinite undo/redo functionality, and support for contributing to Wikidata and other Wikibase instances.
