DEVELOPER WORKSPACE
Private JSON Formatter
Format, validate and minify JSON locally. Compare readable input and output, locate syntax errors and download your result without uploading the payload.
Paste JSON → Format or validate → Copy or download
FOR REPEATED BATCH WORK
Offline JSON Batch Kit
Validate a folder of JSON files and write formatted copies without overwriting originals.
Planned price: $3 one-time. Checkout is not available yet. The browser tool above is free.
See what is included in the $3 kit
Python 3.10+ command-line tool, standalone browser formatter, example JSON, README and internal-use license. Duplicate keys and unsupported numeric ranges are rejected.
No subscription, custom service or future updates are promised.
Download Example JSON freeHow to read your result
Formatting helps review API responses. Validation checks syntax, not an API schema. Unquoted unsafe integers, overflow and nonzero underflow are rejected; quote exact identifiers. Decimal fractions still use binary floating point. Duplicate object names retain their last value.
Related tool: Email Payload Inspector — Attachment & Base64 Size Calculator
Reproduce a known result
Formatting keeps the quoted orderId exact; items remains an array and paid remains false.
Load API response with a quoted large identifier · Download synthetic example
Examples and troubleshooting
A formatter can make a valid API response readable. It cannot decide whether that response has the right fields for your application. Use syntax validation first, then check the shape and values against your API contract.
Fix JSON syntax errors without uploading your payload
Common questions
Does valid JSON mean my API request is correct?
No. A syntactically valid value can have missing fields, wrong types or values your API rejects. Validate against the API contract separately.
Why do I get a trailing-comma error?
Remove the comma directly before the closing } or ]. Keep commas between adjacent members or array values.
Does Engine1 upload my JSON?
The product workspace parses JSON in an isolated browser frame. Anonymous action names are measured by the parent page; the payload itself is not included in those events.
Privacy and anonymous measurement
Your tool inputs stay in the isolated browser workspace. We count page views and action names, anonymous browser IDs, referring domain, campaign channel and device class. We do not collect your JSON, email text, playlists or complete referring URLs. Country is unknown unless supplied by a trusted server configuration. Browser storage may be unavailable; in that case unique-user counts are limited to this visit.
Share the tool, not your input
Add this tool to your docs or resource page
Copy a plain link for your team wiki, tutorial or resource page. It opens the free tool and includes no input data, embedded scripts or account requirement. The docs tag helps us count visits from shared resources.