MiTeC JSON Viewer is a free JSON editor that includes Base64 encoding/decoding, formatting and text search as well as JSON validation.

It is displayed via a tabbed interface that permits either tree view or text previews. It can also display the object/array and value count and will additionally calculate MD5 and SHA1 hashes.

MiTeC JSON Viewer also includes an editor which gives you the option to make changes to JSON files.