Engineering/2025/Active
JSON Downloader
A minimal Chrome extension for downloading JSON data from web pages or URLs with a single click. Automatic JSON detection with a floating download button. Privacy-focused with no tracking or data collection.
Overview
Chrome renders raw JSON responses as plain, unstyled text with no built-in way to save them — fine for eyeballing an API response, useless if you actually need the file. JSON Downloader adds the missing "save" button: a Manifest V3 extension that detects JSON on the current page (or fetches it from any URL you paste in) and writes it to disk as a validated, timestamped .json file.
It's aimed at anyone who works against APIs day to day — pulling a fixture for a test, grabbing a config response, or archiving an endpoint's output without opening DevTools. Everything runs locally in the browser; the extension makes no calls to any server beyond the one it's explicitly told to fetch from.
Key Features
- Automatic JSON detection — a floating "Download JSON" button appears on pages serving raw JSON
- Fetch from URL — paste any public JSON URL into the popup to fetch and download it directly, without navigating there first
- JSON validation — the response is parsed and validated before it's written to disk
- Smart filenames — downloads are saved as
json-download_<hostname>_<timestamp>.json, so batches stay identifiable and sortable - Minimal permissions —
activeTab,scripting,downloads, and host access, nothing else - No tracking or analytics — no data collection, no third-party calls (see the repo's PRIVACY.md)
Installation
Chrome Web Store — install JSON Downloader
Manual / developer mode
git clone https://github.com/chethanyadav456/JSON-Downloader.git- Open
chrome://extensions - Enable Developer mode (top-right toggle)
- Click Load unpacked and select the cloned directory
- The JSON Downloader icon appears in the toolbar
Usage
Floating button — visit any page serving raw JSON (e.g. hitting an API endpoint directly in the address bar) and click the blue button that appears in the top-right corner.
Popup — click the toolbar icon, then either:
- Download from Page — extracts and downloads JSON from the current tab, or
- Fetch & Download — paste a JSON URL to fetch and save it directly
How It Works
The extension is split into three pieces: a content script that scans the page for JSON and injects the floating button, a service worker that formats/validates the JSON and drives Chrome's downloads API, and a popup for manual control. There's no backend — detection, validation, and file writing all happen in the browser via standard Manifest V3 APIs, which is also why the permission list stays short (activeTab, scripting, downloads, plus host access to read JSON from whatever page or URL it's pointed at).