Compare JSON

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Chrome Extension

Compare JSON - Diff API Responses is a Chrome extension that captures JSON API responses on any page and lets you compare two of them on comparejson.com — no copy-pasting from DevTools.

Installation

Install it from the Chrome Web Store, then pin it to the toolbar for quick access.

Capture API Responses

  1. Click the extension icon in the toolbar to open the popup.
  2. Press the Start button (▶) to begin collecting. From that moment on, every JSON response the page receives through fetch or XMLHttpRequest is captured — across all tabs. The toolbar badge shows how many responses have been captured.
  3. Use the web app as usual. Navigating directly to a .json URL (rendered by Chrome’s built-in JSON viewer) is captured too.

Each entry in the popup list shows the HTTP status, method, and URL of the captured response.

Compare Two Responses

  1. Click an entry to mark it as Base (the left side of the diff).
  2. Click another entry to mark it as Contrast (the right side). Click a marked entry again to unmark it.
  3. Press Compare. The extension opens the diff result on comparejson.com in a new tab — the two response bodies are handed directly to the page, nothing is uploaded to a server.

Entries with a grayed-out row can’t be selected: either the response body wasn’t readable, or it exceeded the 2 MB capture limit.

  • Start / Pause — toggle collecting on and off. The collecting state persists across browser restarts.
  • Clear — discard all captured responses.
  • Keep N — how many responses to keep at most (1–1000, default 100). When the limit is reached, the oldest entries are dropped.
  • Reset — clear the current Base/Contrast selection.

Privacy

Captured responses live only in the browser’s session storage and are cleared when the browser closes. When you press Compare, the two selected bodies are passed straight to the comparejson.com tab through Chrome’s extension messaging — they never touch a third-party server.