Free tool
Text and JSON Diff
Compare two blocks of text or JSON and see exactly which lines changed.
Paste the original on the left and the changed version on the right to get a line-by-line comparison. It uses a longest-common-subsequence match, the same approach as diff itself, so moved and inserted blocks line up instead of everything after a single insertion appearing changed.
The JSON mode is the one worth knowing about. Turning it on parses both sides and reprints them with sorted keys and consistent indentation before comparing, which removes the noise from key order and formatting so you see only genuine differences in the data. That is usually what you actually want when comparing two API responses.
How to use it
- Paste the original text on the left and the new version on the right.
- Turn on JSON mode to normalise both sides before comparing.
- Ignore whitespace or case if those differences are not meaningful to you.
- Read the result: minus lines were removed, plus lines were added.
Frequently asked questions
Why does the whole file look changed after one edit?
That happens with tools that compare line N to line N. This one matches common subsequences instead, so inserting a line shifts the rest without marking it changed. If everything still looks changed, check whether line endings differ, which is the usual culprit.
Can I compare two JSON responses meaningfully?
Yes, that is what JSON mode is for. Both sides are parsed and reprinted with sorted keys and uniform indentation first, so differences in key order or formatting disappear and only real data differences remain.
Does it detect a line that simply moved?
Partly. A moved line shows as a removal in one place and an addition in another, which is how standard line diff behaves. It is not a rename or move detector.
Is there a size limit?
A practical one. Comparison cost grows with the product of the two line counts, so beyond roughly two thousand lines each it switches to a faster but less precise comparison and tells you it has done so.
The desktop version
Text and JSON Diff in Toolbelt
This page does the job in a browser tab. Toolbelt is the same tool as a native Mac app, plus the things a web page cannot do.
Tools
{
"name": "Holizmi",
"tools": [
"json",
"jwt",
"base64"
],
"live": true
}{
"sub": "12345",
"name": "Henry",
"exp": 1767225600
}019bd4e2-7a10-7c3e-9f21-4a6b8d3e5c07
019bd4e2-7a11-7b8a-8e44-1c2f9a7d6b13
019bd4e2-7a12-7d5f-b0c9-7e3a1f8c2d95 1 1 one
2 2 two
3 + inserted
3 4 three- Compare two files straight from Finder instead of pasting
- Diff whole folders and see which files differ
- Three-way comparison when resolving a merge by hand
- Works with no connection at all