What does validating JSON mean?

It checks whether your text is syntactically valid JSON. Paste it in and the tool parses it on the spot: if it is well-formed it shows a “valid” badge, otherwise it shows a clear error message together with the line and column where parsing failed. Common mistakes — missing brackets, trailing commas, unquoted keys — are pinpointed instantly.

Can it diff two JSON documents?

Yes. Switch to “Diff two” mode and paste two JSON documents — A (before) and B (after). The tool lists every added key, removed key, and changed value, each labelled with its JSON path such as `a.b[0].c`. You can copy the whole report with one click.

What does a JSON path like a.b[0].c mean?

It describes where a change occurred, traced from the root. Object keys are joined with a dot (`.`) and array elements with a bracketed index (`[0]`). For example `user.tags[2]` means “the 3rd element of the tags array inside the user object”.

What kinds of errors can it catch?

Every syntax error that JSON.parse rejects: trailing commas, mismatched brackets, unquoted keys or strings, single quotes, and unterminated strings. Because it reports the line and column alongside the message, you can jump straight to the fix.

No. Both validation and diffing run entirely in your browser. The JSON you paste is never uploaded or stored on a server.

Yes, it is completely free. No sign-up and no installation required.

JSON validator & diff

JSON tools

Validate JSON with clear error messages, or diff two documents by JSON path. Everything runs in your browser; your data is never uploaded.

What is this JSON validator & diff tool?

A free, browser-based tool that validates JSON and compares two JSON documents. Paste a single document to check whether it is well-formed — invalid JSON is reported with a clear message plus the line and column where parsing failed. Or switch to diff mode and paste two documents to see exactly which keys were added, removed, or changed, each labelled with its JSON path (e.g. a.b[0].c). Everything runs locally in your browser, so your data is never uploaded.

How to use it

Choose a mode: “Validate one” to check a single document, or “Diff two” to compare A and B.
Paste your JSON. Validation runs live as you type.
In validate mode, read the valid badge (with type and key/item count) or the line/column error.
In diff mode, review the added / removed / changed lists, then copy the report.

Common use cases

Debugging an API response or config file that won't parse — find the exact line and column.
Reviewing what changed between two versions of a config, fixture, or payload.
Verifying a hand-edited JSON file before committing or deploying it.

Related tools

FAQ

Operated by

Tools by Timothe AI is a suite of free tools built and operated by unbounded pioneering inc, the company behind Timothe AI.

Ryosuke SuzukiFounder & CEO

Founder & CEO of Unbounded Pioneering Inc., the company behind Timothe AI, and an expert in machine learning and AI product development. He began his career in machine learning research at a university laboratory, then designed and built large-scale products as a software engineer at PLAID, Rakuten, and Recruit, while also driving new business development. Now specializing in generative AI and AI products, he works across both engineering and business development, and is a named inventor on multiple granted patents in web technology.

Named inventor on granted patents JP6887648 & JP7480958 · Patent pending on Timothe AI technology

LinkedIn X About us →

Get in touch

Thanks for reaching out

Thank you for your interest in our company. A member of our team will get back to you within one business day.

What we can help with

Adopting and getting the most out of Timothe AI
A demo or trial of Timothe AI
AI adoption in general (beyond our own product, too)
Alliances and partnerships
Any other questions

Talk to us online

You can also book a meeting directly from the calendar.