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Compare files

Text, JSON & STEP Diff Checker

Compare two texts, JSON documents or STEP files side by side. Highlights minor differences in large dumps — useful for CAD revisions, API payloads and quotes.

Your file is processed locally in your browser. Nothing is uploaded to a server.

+3 added · −2 removed · 4 unchanged

Differences

11 {
2− "holes": 4,
2+ "finish": "zinc",
3+ "holes": 6,
34 "material": "steel",
45 "part": "bracket",
5− "rev": "A"
6+ "rev": "B"
67 }

Why a line diff for CAD and JSON

Quotes, API dumps and STEP files are large. A single changed hole count or revision letter is easy to miss in a scroll. This tool diffs by line: green is added, red is removed. JSON mode pretty-prints and can sort keys so a reshuffled object does not look like a rewrite.

STEP (ISO 10303-21) is text. Two exports of the same part often differ in entity IDs even when the solid is unchanged — that is expected. For geometric size and weight use the STEP quote tool. Pretty-print JSON first with the JSON formatter if you only need one document tidied.

Frequently asked questions

Can I compare STEP or CAD text dumps?+

Yes. STEP/STP files are text (ISO-10303-21). Open two revisions as files or paste them. The diff is line-based, so you will see added or removed entities. It does not do a geometric 3D compare.

How does JSON compare work?+

JSON mode parses both sides, optionally sorts keys, pretty-prints, then diffs the lines. That way a reordered object does not look like a huge change. Invalid JSON falls back to a plain text diff.

Are the files uploaded?+

No. Comparison runs in your browser. Large files stay on the device; only the first few thousand lines of the visual diff are drawn, but you can copy the full unified diff.

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