Free JSON Formatter & Validator — No Upload

🔒 Runs entirely in your browser · Nothing uploaded or saved · Share links never expire · Free, no sign-up

How to format and validate JSON

Paste or open your JSON

Type, paste, or open and drop a local .json file. Nothing is uploaded.

Validate instantly

Valid JSON shows keys, depth and size. Errors show the line and column, with a jump-to-line button.

Format or minify

Pick 2 spaces, 4 spaces or tabs, minify to one line, and optionally sort keys.

Copy, download or share

Copy the output, download a .json file, or copy a private share link that never expires.

A JSON formatter that never sees your data

Most online JSON formatters send what you paste to their server, and some save it behind "share" or "recent links" pages that other people can browse. JSONly parses and formats JSON with JavaScript on your device. There is no upload, no database and no list of saved links. When you share, the JSON is compressed into the link itself, after the #, which browsers never send to a server.

What you can do

Format / beautify JSON with 2 spaces, 4 spaces or tabs, or minify it to one line
Validate JSON with the exact line and column of the first error, explained in plain words
Sort keys recursively, browse a collapsible tree, and see keys, depth and size
Open local .json files, copy the result, download a .json, or copy a share link

Why JSONly?

🚫 No upload: API responses, configs and logs stay on your device
♾️ No saved snippets: share links live only in the URL fragment, so there is nothing to leak or expire
🎯 Exact output: large numbers and string escapes are kept as written
🆓 Free, no sign-up, no limits beyond your device

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Frequently Asked Questions

Is my JSON uploaded anywhere?

No. JSONly parses, validates and formats your JSON with JavaScript in your browser. Nothing you paste or open is sent to ToolBookly or anyone else, and nothing is saved on a server.

Is it safe to paste JSON with secrets?

On JSONly, the JSON never leaves your device, so pasting it here does not expose it. That is not true of every site: in November 2025, security researchers at watchTowr reported collecting more than 80,000 saved JSON snippets, including credentials and API keys, through the save and "recent links" features of popular online JSON formatters. JSONly has no save button, no database and no public list of links. One rule still applies: do not put secrets in a share link, because anyone who has the link can read what is inside it. Read the watchTowr Labs report (25 Nov 2025) ↗

How do share links work without a server?

Your JSON is compressed and placed in the link after the # sign. Browsers never send that part of a URL to a server, so the person who opens the link decodes it on their own device. There is nothing stored for anyone to list, leak or delete.

Do JSONly share links expire?

No. The content lives in the link itself, so it keeps working for as long as the link exists. Large JSON makes a long link; for big files, sending the downloaded .json is often easier.

What errors does the JSON validator catch?

Any input that is not valid JSON (RFC 8259): trailing commas, single quotes, unquoted keys, comments, missing commas or colons, bad escapes, invalid numbers and unclosed strings. JSONly shows the line and column of the first error, explains it in plain words, and can jump straight to it.

Will formatting change my numbers or strings?

No. JSONly keeps every number and string exactly as written, including large IDs beyond JavaScript's safe integer range that many tools silently round. Only whitespace changes, and key order changes only if you turn on Sort keys.

Is there a size limit?

JSONly sets no limit. Files are read locally, so the practical limit is your device's memory; very large files (tens of MB) may take a moment to format and display.

Is JSONly free?

Yes. Free, no sign-up, no usage limits. It is part of the ToolBookly suite of browser tools.