JSON key coverage report
Paste a JSON array of objects to see, for each key found, how often it appears across all objects and the list of objects (by index) where it is missing. Ideal for spotting incomplete data before an import or a migration.
How it works
A JSON array of objects, for example from a converted CSV export or from data aggregated from several sources, often contains objects with slightly different structures. Paste the array and click "Analyze coverage": every key found in at least one object is listed with its presence rate and the indexes of the objects where it is missing.
How are object indexes numbered?
Indexes start at 0, in the order the objects appear in the pasted JSON array. For example, index 0 is the first object in the array. If more than 10 objects are missing the same key, only the first 10 indexes are shown, followed by the total number remaining, to keep the report readable on large datasets.
Does a key with a null value count as present?
Yes: the tool only checks that the key exists in the object (via hasOwnProperty), not the value it holds. A key with the value null, an empty string or 0 is therefore counted as present; only the total absence of the key counts as missing.
100% local processing: the analysis runs entirely in your browser — your data never leaves your device.