Question 1

What is the difference between a text diff and a JSON diff?

Accepted Answer

A text diff compares files line-by-line and character-by-character, meaning changes in spacing, indentation, or the order of object keys will be flagged as massive differences. A JSON diff parses the text into a mathematical data structure in memory and compares the actual values. It completely ignores formatting and object key order, ensuring that only true semantic changes to the data itself are reported.

Question 2

Why does my JSON diff tool say there are no changes when the keys are in a different order?

Accepted Answer

According to the official JSON specification (RFC 8259), a JSON object is explicitly defined as an unordered collection of zero or more name/value pairs. Because the order has no mathematical or programmatic meaning, a high-quality JSON diff tool evaluates {"a": 1, "b": 2} and {"b": 2, "a": 1} as structurally identical. If you need to track key order, you are treating JSON as text, not as data.

Question 3

How do JSON diff tools handle arrays?

Accepted Answer

By default, JSON diff tools treat arrays as strictly ordered lists. If [1, 2] changes to [2, 1], the tool will report that the value at index 0 changed and the value at index 1 changed. However, because developers often use arrays to represent unordered sets, many advanced tools offer a "loose array" or "set comparison" mode. In this mode, the tool ignores the index and simply checks if the elements exist anywhere within the array.

Question 4

What is JSON Patch (RFC 6902)?

Accepted Answer

JSON Patch is a standardized format defined by the Internet Engineering Task Force for expressing a sequence of operations to apply to a JSON document. Instead of just highlighting changes visually, a tool generating a JSON Patch will output a machine-readable array of instructions—such as [{"op": "replace", "path": "/price", "value": 99}]. This allows other software systems to automatically apply the exact same changes to their own copies of the data.

Question 5

Can a JSON diff tool handle massive files, like a 2GB database export?

Accepted Answer

Generally, no. Standard JSON diff tools must parse the entire document into an Abstract Syntax Tree in the computer's RAM. A 2GB text file can easily expand to 8GB or more of memory overhead when represented as objects in languages like JavaScript or Python, instantly crashing the program. For gigabyte-scale JSON, you must use specialized streaming parsers or chunk the data rather than using standard structural diff libraries.

Question 6

Why did my JSON diff tool say 10.0 and 10 are the same?

Accepted Answer

JSON does not differentiate between integers and floating-point numbers; it only has a single Number type. When the diff tool parses the raw text into memory, both "10.0" and "10" are evaluated as the exact same mathematical value by the underlying programming language (typically as an IEEE 754 double-precision float). Because their structural value in memory is identical, the semantic diff correctly reports zero changes.

JSON Diff Tool

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