How does the deep diff work?

The tool recursively compares the two parsed values. For objects it diffs by key; for arrays it diffs by index; for primitives it compares with strict equality. It records additions, deletions and modifications with the full dot path to each leaf, like config.server.port.

How are arrays compared?

Arrays are compared positionally — index 0 against index 0, and so on. An element present only in the longer array counts as added or removed. This matches how most config and data files are edited; reordering an array will therefore show as changes.

What counts as a change versus add or remove?

A key present in both documents but with a different value is a change (shown with old → new). A key present only in the second is an addition; a key present only in the first is a removal. Type changes, such as a number becoming a string, count as a change.

Does key order matter?

No. JSON objects are unordered, so the diff compares by key name, not position. Reformatting or reordering object keys produces no differences. Only array element order matters, because arrays are ordered.

Is my JSON sent anywhere?

No. Parsing and diffing happen entirely in your browser with JSON.parse and plain JavaScript. No data is transmitted, so the tool works offline and your documents stay private.

JSON Diff — Gera Tools

Compare two JSON documents and see precisely what changed — every added, removed and modified field, addressed by its dot path and color-coded. The diff runs entirely in your browser with JSON.parse and a recursive structural walk; nothing is uploaded.

How it works

The tool parses both inputs, then recursively compares the two values:

Objects are compared key by key. A key in both with differing values is a change; a key only in the right document is an addition; a key only in the left is a removal.
Arrays are compared by index — element 0 against element 0. Extra elements in the longer array are additions or removals.
Primitives (string, number, boolean, null) are compared with strict equality. A type change, such as "42" versus 42, is reported as a change.

Each leaf difference is recorded with its full dot path, for example:

+ user.roles[2]        = "admin"        (added)
- user.legacyId                          (removed)
~ server.port          42 → 8080        (changed)

Because objects are unordered, reformatting or reordering keys produces no differences — only real value changes show up. Array order, however, is significant.

Tips

To compare two API responses, paste each whole body; the dot paths make it easy to locate a changed field deep in a nested structure.
If you see a long list of array changes after only a small edit, an element was likely inserted near the front, shifting every later index — positional diffing reports each shifted slot.
Pretty-print or minify makes no difference to the result; whitespace is irrelevant once parsed.