How to Compare Two JSON Objects
Comparing two JSON documents sounds like comparing two files, and it is not. A plain text diff reports every difference in the characters, and most of those differences do not matter. The JSON Diff Checker compares the structure instead and reports what actually changed.
Why a text diff misleads
Key order is meaningless in JSON. An object with name before email means exactly the same as one with email before name. A text diff reports both lines as changed and tells you nothing.
Whitespace is meaningless too, so one document formatted and one minified diff completely while being identical in content. So does a change in indentation, a trailing newline, or a different line ending between Windows and Linux.
Then there are the differences that look cosmetic and are not. The number 1 and the string "1" are different values. The number 1.0 and 1 are the same value written differently, and whether your comparison says so depends on the tool. A missing key and a key present with a null value are genuinely different things, and conflating them is the source of real bugs.
What a structural comparison does
It parses both sides and walks the tree, reporting three kinds of finding: a key present on one side only, a key whose value differs, and - the one that matters most in practice - a nested object or array that differs somewhere inside.
Arrays are the hard part, because order usually does matter in an array and sometimes does not. A list of tags is probably a set, where reordering is no change at all. A list of steps is a sequence, where reordering is the whole change. No tool can know which you meant, so read array differences with that in mind.
Before you compare
Format both sides first with the JSON Formatter and you will often spot the answer without any comparison, especially if one side is invalid rather than different. If a document will not parse, there is nothing to compare until it does.
For a large pair, narrow before you diff. Comparing two thousand-line API responses in full produces a report as unreadable as the originals; comparing the one branch you care about does not.
Common questions
Why does the tool say nothing changed when the files differ?
Because the differences were whitespace or key order, which carry no meaning. That is the right answer.
Can I compare JSON against CSV?
Not directly. Convert the CSV with the CSV to JSON Converter first so both sides are the same shape.
Is a null the same as a missing key?
No, and treating them as equal hides bugs. A missing key usually means never set; a null usually means deliberately cleared.
Does it matter that one file is minified?
Not to a structural comparison. It matters enormously to a text diff, which is the point.
Is my data uploaded?
No. The comparison happens in your browser, which matters when both sides are production records.
Got two versions to compare?