jsonkeyper.com

A free, browser-based JSON key extractor. Paste any JSON object and get every key path it contains - including keys buried inside nested objects and arrays - rendered as dot notation, JSONPath, an indented tree, or a generated TypeScript interface.

Live at jsonkeyper.com.

Everything runs client side. No JSON is uploaded, logged, or stored anywhere; the page keeps working with the network disconnected.

Features

Output format	What it gives you
Key paths	user.address.city, orders[0].total - paste straight into code
Key paths with value types	The same paths annotated string, number, object, ...
Unique key names	A sorted, deduplicated vocabulary of every key name
JSONPath	$.user.address.city, with [*] wildcards when indices are collapsed
Indented tree	A visual read of shape and nesting depth
TypeScript interface	A generated interface Root { ... } from your sample

Alongside those:

• Collapse array indices - merges items[0].sku and items[1].sku into a single items[].sku, which is what you want when documenting a schema rather than inspecting one record.
• Structure statistics - total key paths, unique key names, maximum nesting depth, object and array counts, and payload size.
• Input options - paste, drag a .json file onto the input box, use the file picker, or load the built-in sample. Ctrl / Cmd + Enter extracts.
• Useful parse errors - reports the line and column of malformed JSON rather than a generic failure.
• Copy or download - to the clipboard, or as .txt (.ts for the TypeScript format).

The TypeScript generator merges objects across an array and marks any key absent from some elements as optional, so a giftMessage present on only one of two orders is emitted as giftMessage?: string.

Known limitations

These are deliberate, and documented on the site itself:

• Type inference describes the sample you paste, not the API's real contract. A field that happens to be null in your sample is typed null.
• The full path list is built in memory, so documents in the tens of megabytes may be slow. Use a streaming tool such as jq at that scale.
• JSON does not distinguish integers from floats, so every number is number.
• Dot-notation output is ambiguous for keys that themselves contain a dot. The JSONPath output quotes those instead.
• It validates that JSON parses; it does not validate against a JSON Schema.

Repository layout

index.html          Tool plus reference content, FAQ, and structured data
script.js           Traversal, output formatters, and UI wiring (no dependencies)
styles.css          All custom styling; Bootstrap 4.5.2 is loaded from a CDN
about.html          Project background, capabilities, limitations, author
contact.html        Contact form (composes a mailto:)
privacy.html        Privacy policy
terms.html          Terms of service
blog/index.html     Article listing
blog/*.html         Eight long-form guides on working with JSON
sitemap.xml         Kept in sync by hand when pages are added
robots.txt          Allows all crawlers, points at the sitemap
CNAME               Custom domain for GitHub Pages

There is no build step, no bundler, and no package manifest - the files served are the files in the repository.

Running locally

Any static file server works. The site uses root-relative links (/blog/), so serve from the repository root rather than opening index.html over file://:

python3 -m http.server 8000
# then open http://localhost:8000

Deployment

Pushes to main trigger .github/workflows/static.yml, which publishes the whole repository to GitHub Pages. There is no staging environment, so a merge to main goes live immediately. Work on a branch and open a pull request.

Contributing

Issues and pull requests are welcome. A few conventions worth knowing:

• Match the existing style. Vanilla JS with inline onclick handlers for the tool controls, four-space indentation, and no new runtime dependencies.
• Use hyphens, not em dashes, in page copy.
• Update sitemap.xml when you add or remove a page.
• Keep dates honest. Article datePublished / dateModified values, visible bylines, and sitemap lastmod entries must reflect when the content was actually written.
• Test the tool before opening a PR. script.js exposes plain functions, so the formatters can be exercised directly under Node without a browser.

License

MIT - Ashish Singh.