Question 1

What is a JSON diff?

Accepted Answer

A JSON diff shows the structural differences between two JSON documents. It highlights which keys were added, removed, or modified — including nested objects and arrays. JSON diffing is commonly used in code reviews, API response comparison, configuration auditing, and debugging data pipelines.

Question 2

How does the JSON Diff Viewer handle arrays?

Accepted Answer

The viewer uses the jsondiffpatch algorithm which computes the Longest Common Subsequence (LCS) for arrays. This means it can detect moved, added, and removed array items rather than naively treating every index change as a modification. The result is a more meaningful diff that reflects actual data changes.

Question 3

Is my JSON data sent to a server?

Accepted Answer

No. All diffing is performed entirely in your browser using client-side JavaScript. Your JSON data never leaves your machine, making this tool safe for sensitive configuration files and private API payloads.

Question 4

What do the summary badges (added / removed / changed) mean?

Accepted Answer

Added counts fields or array items that exist only in the right JSON. Removed counts fields or array items that exist only in the left JSON. Changed counts fields whose values differ between the two documents. These counts help you quickly assess the scope of changes before reading the detailed diff.

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JSON Diff Viewer

Left JSON

Right JSON

Diff Output