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JSON Validator

RFC 8259In-browser only
Ln 1, Col 114 lines · 254 bytes
Result✓ Valid RFC 8259
Root: objectDepth: 412 items254 B (-64 B minified)
Object (5 keys)
{
"JSON iGraph",
"1.0.0",
true,
[
"RFC 8259",
"ECMA-404"
],
{
true,
"line-and-column",
{
3,
true
}
}
}
17 lines · 266 bytes
Help

Validate JSON against RFC 8259 with line and column error pointers, fix suggestions, and 1-click auto-repair — 100% in-browser.

01-03 Guide

How to validate JSON in 3 steps

Pinpoint syntax defects, understand standard RFC violations, and repair payloads with one click.

    payload.jsonInput
    {
    'user': "Ada",
    "roles": ["admin",]
    }
    Paste or uploadSyntax Scan
    01

    Paste or upload JSON

    Paste or upload your raw JSON payload into the editor.

    Line 3, Col 18Diagnostic
    2 | 'user': "Ada",
    > 3 | "roles": ["admin",]
    ^ Trailing comma
    RFC 8259 violationExact Pointer
    02

    Inspect line pointers

    Inspect real-time syntax validation with exact line numbers, columns, and visual caret pointers.

    ✓ 1-Click Auto-FixClean Output
    ⚡ Auto-Fix
    →
    Valid JSON
    Copy & DownloadReady to use
    03

    Auto-repair & export

    Click 1-Click Auto-Fix to automatically repair common syntax violations, or export the verified payload.

Developer Superpowers

Built for developers who hate cryptic errors

^

Visual Caret Pointers

See the exact line, column, and character that triggered the error, eliminating guesswork on huge payloads.

⚡

1-Click Auto-Repair

Instantly fix single quotes, missing key quotes, JS comments, and trailing commas without manual editing.

📊

Structure Analytics

Inspect root type, maximum object depth, key count, and exact byte savings between raw and minified text.

🔒

Zero-Upload Privacy

100% in-browser processing. Your proprietary API payloads, credentials, and tokens never touch a network server.

Standards Guide

Understanding RFC 8259 vs. JavaScript Object Literals

JSON is derived from JavaScript object literal syntax, but it is a strict subset. Many constructs permitted in modern JavaScript (such as trailing commas, single-quoted strings, unquoted property identifiers, and comments) are invalid in RFC 8259 JSON.

When an API or microservice uses strict parsers (such as standard library parsers in Go, Rust, Java, or Python), any non-compliant syntax causes the entire HTTP request to fail with a 400 Bad Request error. Validating your payloads before deploying or mocking saves hours of debugging time.

Standard ComparisonRFC 8259 Strict
JavaScript Literal (Invalid JSON){ user: 'Ada', }
RFC 8259 Valid JSON{"user": "Ada"}
Checklist

RFC 8259 Rules at a Glance

The 5 core rules our engine checks against:

  • 1Keys must be double-quoted strings
  • 2No trailing commas after items or keys
  • 3Strings must use double quotation marks (")
  • 4No comments permitted (neither // nor /* */)
  • 5Numbers cannot have leading zeros (e.g. 01)
100% IN-BROWSERSANDBOXED

Validation and repair execute in your browser with zero network latency — your JSON is never sent anywhere.

Answers

Frequently asked questions

Everything you need to know about JSON syntax validation and standards compliance.

Which JSON specification does this validator enforce?
This validator strictly enforces IETF RFC 8259 and ECMA-404 data interchange standards. It validates data types, string quoting, escape sequences, number formats, and structural enclosures.
Why are trailing commas rejected by the validator?
RFC 8259 Section 4 (Objects) and Section 5 (Arrays) explicitly specify that commas separate items and cannot follow the last item. While JavaScript and TypeScript permit trailing commas, strict JSON parsers and APIs will reject them.
Can I include comments in standard JSON?
No. Standard RFC 8259 JSON does not support comments (neither // single-line nor /* */ block comments). If you need comments in configurations, consider JSONC (JSON with Comments) or JSON5.
How does 1-Click Auto-Fix work?
Auto-Fix scans the payload for common human and copy-paste syntax errors: it strips line and block comments, normalizes single quotes to double quotes, wraps unquoted object keys in double quotes, and removes trailing commas.
Is my data transmitted to any external server?
Never. All validation, parsing, structure calculation, and auto-repair run 100% locally in your web browser. Nothing you type or paste is logged or transmitted.
Why are single quotes not allowed for strings or keys?
RFC 8259 Section 7 strictly mandates that strings and keys begin and end with double quotation marks (U+0022). Single quotes are valid in Python and JavaScript literals, but are invalid in JSON.

Related tools

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Graph Visualizer — Live

Stop reading raw brackets. Start seeing connections.

Paste the same JSON into the graph and see it as connected nodes you can search, fold and export — completely free and in-browser.

Open JSON Graph →Back to Validator ↑
VALIDATED NODE GRAPHRFC 8259
Status: Valid───>Visual Nodes
0ms server latency · 100% private