JavaScript Object Diff Viewer - Online Compare Data

A JSON Object Diff Viewer is a developer tool that compares two JSON data structures and highlights every difference between them — added keys, removed keys, and modified values. It's invaluable for debugging API responses, tracking configuration changes, reviewing database migrations, and validating data transformations without manually scanning through nested objects.

Our tool recursively traverses every level of both JSON objects, collecting all leaf-node paths and their values. It then compares paths across both objects to identify added (exists only in Object B), removed (exists only in Object A), and changed (exists in both but with different values) entries. This works for arbitrarily deep nesting, including nested objects and arrays at any depth.

Arrays are compared by index position. Each element is treated as arrayName[index] in the path. If an array has additional elements in Object B, they appear as added. Missing elements appear as removed. Modified elements at the same index are marked as changed. For large arrays, this index-based comparison gives you precise visibility into exactly which positions differ.

Absolutely secure. All comparison happens entirely in your browser using client-side JavaScript. No data is ever sent to any server, uploaded, stored, or logged. Your JSON data never leaves your device. You can safely compare sensitive configuration files, API payloads containing tokens, or proprietary data structures with complete privacy.

The tool accepts standard RFC 8259 JSON — objects, arrays, strings, numbers, booleans, and null values. Keys must be double-quoted, and trailing commas are not allowed. If your input isn't valid JSON, a red indicator will appear, and the tool will alert you before comparison. You can use the Format button to auto-format valid JSON with proper indentation for readability.

Yes, the tool handles reasonably large JSON objects (up to several megabytes) efficiently. Since processing happens locally in your browser, performance depends on your device. For extremely large datasets (10MB+), you may experience slight delays during comparison. We recommend formatting and validating large JSON files before comparison for the best experience.

GREEN — Added: This key exists in Object B but not in Object A.
RED — Removed: This key exists in Object A but not in Object B.
YELLOW — Changed: The key exists in both but the value differs. The old value is shown in red with strikethrough, and the new value in green.

Traditional code diff tools compare raw text line-by-line and can miss semantically meaningful changes in JSON structure (like reordered keys or reformatted whitespace). Our tool parses both inputs into actual JavaScript objects and compares them structurally, so formatting differences are ignored and only real data changes are surfaced. This gives you a much more accurate view of what actually changed in the data.