Help Centre

Find answers to common questions, learn how Jsontell works, and understand its limits. If you are stuck, start with the FAQs below.

Getting started

Choose your mode

Jsontell has two modes. Use URL mode when an API endpoint is returning something you did not expect. Jsontell fetches the URL server-side, inspects the actual response (content-type, status, body), and tries to parse it as JSON. Use Paste mode when you have JSON text and just want to know where the syntax error is - parsing happens entirely in your browser; nothing leaves your machine.

Enter your input

In URL mode, paste the full URL including https:// and click Fetch and diagnose. In Paste mode, paste your JSON text into the textarea and click Parse.

URLs behind Cloudflare cannot be reached from the Jsontell Worker. The tool will report such hosts as unreachable.

Read the diagnosis

Jsontell shows a structured result:

A verdict badge - Valid, Invalid, or Warning
The exact location of parse errors (line, column, byte)
The byte that was found there and what was expected instead
For URL fetch: the actual Content-Type, HTTP status, and whether the body is JSON at all

Responses are truncated to 2 KB in the free tier. The full body preview is a planned Professional feature.

Interpret the results

A "valid" verdict means the text parses as syntactically correct JSON. It does not mean the structure matches your expected schema - that is validation, which Jsontell does not do. A "Content-Type mismatch" warning means the server claimed application/json but sent something else (like text/html) - a common sign of an error page.

Frequently asked questions

Why does my URL return "unreachable"?

Jsontell's fetch runs on a Cloudflare Worker. A host that is itself behind Cloudflare's network cannot be reached from a Cloudflare Worker due to Cloudflare's own network architecture - the request appears to come from Cloudflare, so the host treats it as a loopback and drops it. This is a hard platform limit, not a bug in Jsontell.

Workaround: Try accessing the endpoint from a non-Cloudflare environment (your local machine, a VPS, curl from a terminal). Or use Paste mode with a copy of the response body. There is no way to bypass this from within the tool.

The tool says my JSON is valid, but my API rejects it. Why?

JSON validity (syntax) and JSON validation (schema) are different things. Jsontell checks syntax only. Your API probably uses a schema - it expects certain fields, types, or values. For example, {"name": 42} is valid JSON, but if the API expects name to be a string, it will reject it. Jsontell does not do schema validation.

What to do next: Check your API's documentation for the expected schema. Some APIs return their own validation errors in the response body - use Jsontell's URL mode to fetch the endpoint and see what the server actually replies with.

Can I save my results or review them later?

No. Jsontell has no accounts, no user database, and no persistent storage. Each diagnosis is a single request-response cycle - once you close or reload the page, the result is gone. There is no way to create an account, log in, or retrieve past results.

If you need to keep a record, copy the diagnosis text manually before leaving the page.

Why is my response body truncated? How do I see the full response?

The free Starter tier truncates response previews at 2 KB. This is a platform-level limit to keep response sizes manageable for the Cloudflare Worker.

Full body preview (up to 10 MB) is part of the Professional tier, which is planned but not yet available - no payment processor is connected yet, so no upgrades can be processed. See pricing for details.

Tip: You can use curl -i <URL> from a terminal to see the full response body right now, at no cost.

Does Jsontell store the URLs or data I submit?

In Paste mode, the JSON text never leaves your browser - parsing is entirely client-side via JSON.parse. Nothing is sent over the network.

In URL mode, the fetch happens on the Cloudflare Worker. The response is streamed back to your browser and discarded. Jsontell does not log, cache, or persist URLs, responses, or any data from the request. See the privacy policy for more detail.

What does "unexpected token at position 4471" actually mean?

Standard JSON parsers report errors as byte offsets because that is what the parser sees internally - a flat sequence of bytes. Position 4471 means "the 4,471st byte in the file," which tells you nothing about where in the document structure the error is. Jsontell's purpose is to convert that to something readable: line 3, column 5, expected a colon or a closing brace.

Example: A missing comma between two array elements might produce "position 4471" in a standard parser. Jsontell points at Line 42, column 22. Expected ',' or ']', got '{' - the exact place and what should have been there.

Known limitations

Jsontell is an early-stage tool. Some features are not yet built, and some platform limits are inherent. We believe in being upfront about what this tool cannot do.

No email or contact form There is no email address or contact form on any domain in this fleet. Support by email is not yet available. We are working on setting up a contact channel.
Cannot reach Cloudflare-hosted origins A host behind Cloudflare cannot be reached from a Cloudflare Worker. This is a platform-level constraint, not a configurable setting.
No accounts, history, or saved results Jsontell has no user database or persistent storage. Each session is stateless. There is no way to save, retrieve, or share a diagnosis.
No schema validation Jsontell checks JSON syntax only. It does not validate JSON structure (field names, types, required keys) against any schema.
No alerts, reminders, or scheduled checks Jsontell does not send email, push notifications, or perform recurring checks. There is no email sender configured.
2 KB response truncation (Starter) URL responses over 2 KB are truncated in the preview. Full body support is planned for the Professional tier. Planned
15-second fetch timeout URL fetches time out after 15 seconds. Long-running endpoints may not complete.
No payment processor The pricing page checkout is a demonstration only. No real payment is taken, and no paid tier access can be granted yet.
No legal entity No legal entity has been registered. The operator must supply the entity name, address, and jurisdiction before terms or privacy policy are binding.
No crawl, no redirect following, no retry Jsontell fetches the exact URL you provide. It does not follow redirects, crawl linked resources, or retry on failure.

How to contact us

Support by email is not yet available - there is no mailbox configured on any domain in this fleet. We are working on setting up a contact channel. In the meantime, the best thing you can do is check the tool and this Help Centre for answers.

Use the tool Back to home

This notice will be updated when a support channel becomes available.