Help Centre
Getting started
Whatsjson is a JSON diagnostic tool. You can use it in two ways:
- Check a URL — Enter an API endpoint URL. The tool fetches it, inspects the response (content-type, status code, body), and tells you exactly where and why parsing fails — in plain English, not "unexpected token at position 4471."
- Paste JSON — Paste a blob of JSON text directly. Parsing happens entirely in your browser — nothing is sent to any server.
No registration or account is required to use either mode. Open the tool page and start diagnosing.
Frequently asked questions
Whatsjson says "unexpected token" — what does that actually mean?
Whatsjson doesn't stop at "unexpected token." It points to the exact line and column where parsing failed and translates the error into plain language. For example, instead of unexpected token at position 4471, it might say "Trailing comma after the last value in an object is not allowed at line 14, column 3." It also shows the surrounding lines so you can see the context. If the body isn't JSON at all (e.g., it's HTML or plain text), the tool tells you that too.
The tool says the URL fetch failed / "not established" — but I can reach the URL from my browser. Why?
The most common cause is Cloudflare protection. The Worker that fetches URLs runs on Cloudflare's infrastructure, and Cloudflare does not allow its Workers to reach other Cloudflare-hosted domains. If the target server uses Cloudflare, the fetch will fail, even though the URL works fine from your browser. Try pasting the response body directly in the "Paste JSON" tab instead. If the target is not behind Cloudflare but still fails, the server may be blocking the Worker's IP range or the URL may be unreachable from the edge network generally.
Does Whatsjson store the URLs or JSON I submit?
No. There are no user accounts, no databases, and no persistent storage. For URL checks, the URL is sent once to the Worker which fetches the endpoint and returns the result to your browser — no check history is retained anywhere. For pasted JSON, parsing happens entirely in your browser and the text never leaves your device. There is no way for us to later see what you checked.
The server returned a 200 status but Whatsjson says there's an error object — what's going on?
Many APIs return a 200 HTTP status with a JSON body that contains an error indicator (e.g. {"success": false, "error": "..."}). Whatsjson detects this pattern and flags it as a "disguised failure" — the server said everything is fine at the HTTP level, but the payload itself indicates a problem. This is one of the most common sources of confusing API behaviour, and the tool was specifically designed to surface it.
Can Whatsjson distinguish between invalid JSON and the server sending back HTML or an error page?
Yes. URL checks report the server's actual content-type header and whether the body is JSON at all. If an API returns an HTML error page (e.g. a 502 gateway timeout page served as text/html) or an XML response when you expected JSON, the tool shows you what was actually received. It also reports the status code, body length, and a reliability indicator for the diagnostic, so you can see when a "parse error" is really a wrong-content-type problem.
Is there an API or batch checking? Can I check URLs programmatically?
Not yet. Batch URL checking and programmatic API access are planned for the Pro tier but are still in development. They are not currently available. The Free tier supports one-off URL checks through the web interface only. See the pricing page for the current roadmap.
Known limitations
Whatsjson is an early-stage tool. The following are honest, current limitations:
- Cloudflare-hosted targets cannot be reached — as noted above, the Worker cannot fetch URLs protected by Cloudflare. This is a platform constraint and cannot be worked around from the current architecture.
- No batch checking — each URL check must be done individually. Batch mode is listed on the Pro roadmap.
- No programmatic API — there is no REST API, no SDK, and no way to automate checks from a script. This is also on the Pro roadmap.
- No check history — results are displayed once and are not stored or retrievable later. There is no account system.
- No email, alerts, or notifications — the service has no email sender and cannot deliver results, reminders, digests, or scheduled checks. There is no way for the tool to contact you.
- No legal entity registered — the operator has not yet registered a company or legal entity. The site's terms, privacy notice, and billing commitments are accurate descriptions of intended practice but are not yet legally binding in any jurisdiction.
- Pro tier is not yet available — the $9/month Pro plan is listed on the pricing page with its intended feature set. It cannot be purchased, no payment is being accepted, and no subscriber data is being collected.
- Single-region edge network — the Worker runs on Cloudflare's global network, but fetch latency to the target URL depends on where both the Worker and target are located.
Contact
Whatsjson does not yet have a support email address, contact form, or customer service channel. No legal entity has been registered, so there is no organisation behind the tool that can receive or respond to inquiries.
If you need to reach the operator about a specific concern — such as an abuse report, a legal request, or a significant bug that is not answered by the FAQ above — the operator needs to establish a contact method. This page and the needs.md file will be updated when one becomes available.
For now, the best way to find answers is this Help Centre page and the information on the homepage.