Validate and pretty-print in one pass
Log lines and webhook payloads often arrive as one unreadable string. Before you commit a fixture or paste into Postman, you need to know the JSON is valid and readable. This page runs JSON.parse and JSON.stringify with 2-space indent on every input event. No submit button.
Valid input gets a green status banner, line-number gutter, and enabled Copy output. Invalid input keeps the alert region assertive with line and column when available. The snippet under the alert reprints the failing line with a caret at the column.
Empty textarea: empty output, no alert, copy disabled. That is intentional, not a silent success.
When to use this vs the full formatter
Need minify, tab indent, or auto-fix for Slack paste and JS object literals? Open the JSON Formatter and Minifier. This page is the fast path when you only need RFC 8259 validation and readable output.
YAML configs start from JSON on many teams. After you validate here, dump to YAML with the JSON to YAML Converter. JWT payloads are three Base64 segments, not one JSON blob: use the JWT Decoder instead of parsing the whole token as JSON.
Regex against the pretty output belongs in the Regex Tester. This page does not schema-validate keys or run JSONPath.
Copy and line numbers for reviews
Copy uses the Clipboard API with a 1px textarea fallback. Load sample fills a small valid object so you can confirm the gutter and banner. Clear wipes input and output.
Line numbers help code review on pasted payloads. They are display-only, not part of the copied text. Download is not on this page; copy is enough for most paste targets.
Hard parse failures stay on the alert. There is no partial repair. Fix the source and the output updates live.
Frequently Asked Questions (FAQ)
How is JSON validated on this page?
The input runs through JSON.parse on every keystroke. Success shows a green Valid JSON banner and 2-space pretty output. Failure shows an assertive alert with line and column when the engine reports a position, plus a caret snippet under the failing line.
What is the difference from the JSON Formatter and Minifier?
This page is validate plus pretty-print only. No minify, no tab indent, no auto-fix for trailing commas or JS object literals. For full indent options and compression telemetry, use the JSON Formatter and Minifier on the same site.
Does copy work on invalid JSON?
Copy output stays disabled until parse succeeds. Empty input clears output with no error. That prevents exporting a blank or stale document after a syntax failure.
Is my JSON uploaded anywhere?
No. Parse, stringify, and copy all run in the tab. Use this for API bodies, config snippets, and secrets you would not paste into a hosted beautifier.