OpenRefine is a powerful free, open source tool for working with messy data: cleaning it; transforming it from one format into another; and extending it with web services and external data.
Main features:
- Faceting - Drill through large datasets using facets and apply operations on filtered views of your dataset.
- Clustering - Fix inconsistencies by merging similar values thanks to powerful heuristics.
- Reconciliation - Match your dataset to external databases via reconciliation services.
- Infinite undo/redo - Rewind to any previous state of your dataset and replay your operation history on a new version of it.
- Privacy - Your data is cleaned on your machine, not in some dubious data laundering cloud.
- Wikibase - Contribute to Wikidata, the free knowledge base anyone can edit, and other Wikibase instances.
Note: While the software is classified as free, it is actually donationware. Please consider making a donation to help support development.