JSON Swiss

JSON Swiss

JSON Validator and Syntax Checker

JSON Input

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Validation Results

Start validating JSON

Enter JSON to see validation results

How to validate JSON and find errors quickly

1Paste, import, or hand off the raw JSON2Read errors, warnings, and statistics together3Fix by location, and switch to Repair JSON when needed4Export the report and move the clean JSON downstream

The most effective way to use the validator is to place it at the start of your JSON workflow. Paste in the raw API response, config file, or log payload first, let the tool tell you whether it is valid, where it breaks, and whether there are structural risks, then decide whether to fix it manually, send it to Repair JSON, or continue to formatting, comparison, and schema generation.

Find the problem before guessing at the fix

The validator does more than say invalid - it shows what broke and where

A lot of JSON does not just look messy; it is actually unparseable. The validator is useful because it tells you where the JSON breaks, what kind of issue it is, and whether there are broader structural risks that matter downstream.

JSON to validate
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{
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"orderId": "SO-1024"
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"items": [
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{
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"sku": "A-1",
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"qty": 2,
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}
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]
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}
Validation feedback
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Error 1
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Line 3, Column 3: Expected "," or "}"
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.
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Error 2
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Line 7, Column 5: Trailing comma is not allowed
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.
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Statistics
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Objects: 2
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Arrays: 1
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Max Depth: 3

When there are multiple errors in the same payload, scan the full list first, then decide whether to fix it manually or send it to Repair JSON.

3 validator examples that match real work

These examples cover the most common validation scenarios in development, testing, and operations: API responses, configuration files, and log payloads.

API Debugging

Catch a missing comma in an API response immediately

Useful during API debugging, webhook testing, and response inspection when you need to know whether the backend returned malformed JSON or the payload was copied incorrectly.

Invalid JSON (missing comma)
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{
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"user": {
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"id": 42,
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"name": "Maeve"
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}
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"roles": ["admin", "editor"]
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}
Validation Results
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Error
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Line 6, Column 3: Expected "," or "}"
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.
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Suggestion
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Add a comma after the "user" object

This is exactly the kind of issue the validator handles best: mostly-correct JSON with one local syntax break.

Configuration

Spot trailing commas and comments before a deploy fails

A common problem is treating JavaScript object syntax as if it were valid JSON. The validator helps separate what JS allows from what strict JSON actually accepts.

Invalid JSON (missing comma)
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{
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"env": "prod",
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"retry": 3, // retry count
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"features": {
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"betaCheckout": false,
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}
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}
Validation Results
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Error
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Line 3, Column 15: Comments are not allowed in JSON
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Line 6, Column 3: Trailing comma is not allowed
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.
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Result
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Remove the comment and trailing comma

Running config through the validator before release is usually faster than debugging config failures in production.

Log Review

Use warnings and stats to catch structural risk even when JSON is valid

Some payloads parse successfully but are still risky because of depth, field shape, or payload size. Warnings and statistics help expose that early.

Invalid JSON (missing comma)
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{
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"event": "audit",
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"payload": {
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"meta": {
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"trace": {
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"deep": {
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"nested": {
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"value": "..."
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}
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}
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}
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}
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}
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}
Validation Results
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Validation Result
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OK - JSON is valid
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.
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Warning
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Payload depth is high and may be harder to transform or inspect downstream
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.
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Statistics
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Objects: 6
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Max Depth: 6

Even when JSON is valid, warnings and stats can tell you that downstream processing will be more expensive.

  1. 01

    Tutorial Step

    Step 1 - Paste, import, or hand off the raw JSON

    Start by putting the raw JSON into the input editor. You do not need to clean it up first. One of the main benefits of the validator is catching syntax problems early instead of discovering them only after you send the data to an API or save it as configuration.

    • Paste the full JSON into the editor for quick checks of API responses, webhook payloads, environment config, or log fragments.
    • If the JSON already lives in a file, URL, or clipboard source, use Import instead of manually copying content around.
    • When debugging logs, use the rawest version of the JSON first so you can tell whether the issue comes from the data itself or from a later formatting step.
    • Single-line JSON is fine. Monaco diagnostics and structural statistics still work without pre-formatting the input.
    • Validation updates as you type, so the page also works well as a lightweight live JSON linter.
  2. 02

    Tutorial Step

    Step 2 - Read errors, warnings, and statistics together

    Most people only look at the first error message, but the faster approach is to read the errors panel, warnings panel, and statistics together. Errors tell you what is already broken, warnings tell you what may break later, and statistics tell you how complex the payload really is.

    • Start with the errors list and focus on missing commas, bracket mismatches, invalid escapes, comments, and quote issues.
    • Then review warnings to catch deep nesting, oversized strings, or inconsistent structural patterns before they become downstream problems.
    • Use the statistics panel to understand the number of objects, arrays, keys, and the maximum depth of the payload.
    • When a JSON file has multiple issues, do not stop after the first one. Scan the full list first so you can tell whether the problems are isolated or systemic.
    • If you need to hand the problem off to someone else, the report plus the diagnostics is much more useful than a screenshot alone.
  3. 03

    Tutorial Step

    Step 3 - Fix by location, and switch to Repair JSON when needed

    The goal here is not to delete characters blindly. Use the location and context around each error to understand why the JSON broke. Most invalid JSON falls into a small set of patterns: missing commas, single quotes, comments, trailing commas, unmatched brackets, or nested JSON strings that need another pass.

    • Click an error or warning to jump to the exact line and column, then inspect the nearby commas, quotes, brackets, and comments.
    • Typical fixes include adding commas, closing arrays or objects, replacing single quotes with double quotes, and removing trailing commas.
    • If the payload contains escaped JSON strings inside other JSON, it is usually safer to inspect those inner structures first instead of guessing at the outer syntax.
    • When the file is heavily damaged or the error list is long, move to Repair JSON and let it fix common syntax issues before coming back for validation.
    • After the payload passes validation, scan the warnings and statistics again so you do not miss structural risks that survived syntax repair.
  4. 04

    Tutorial Step

    Step 4 - Export the report and move the clean JSON downstream

    Once the JSON is valid, it is ready for the rest of your workflow. Export a validation report if you need traceability, then move to the formatter, compare tool, schema generator, or table editor based on what you need next.

    • Export the validation report for tickets, debugging notes, API contract reviews, or handoff documentation.
    • If the next step is readability and consistent formatting, continue to the formatter for pretty-printing, minifying, or key sorting.
    • If you want to compare versions reliably, validate both inputs before moving to the compare tool so syntax errors do not pollute the diff.
    • If you want to generate a schema, types, or review data in a table, validated JSON is a much more stable starting point.
    • Putting the validator at the beginning of the workflow usually saves rework later when debugging APIs, editing configs, or generating code.

A more reliable validator workflow

1

Paste the rawest version of the JSON into the validator instead of pre-editing it first.

2

Read the errors, warnings, and statistics together so you understand both syntax failures and structural risk.

3

Fix small issues in place, but switch to Repair JSON when the payload is heavily damaged or the error list is long.

4

Once the payload is valid, move it to the formatter, compare tool, or schema generator for the next stage of work.

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If you need to collaborate, export the report instead of sending screenshots so others can reproduce the problem faster.

Placing the validator at the start of your JSON workflow usually surfaces most downstream problems early, especially during API debugging, config review, and log analysis.

Quick tips

If the first error looks wrong, check the previous line first. The real problem is often one level earlier.
JSON requires double quotes for keys and strings. Single quotes, comments, and trailing commas are common mistakes.
If the payload validates but still feels hard to read, move it to the formatter before continuing.
Before sending JSON to Repair, Compare, or Schema tools, a validation pass usually gives you a cleaner start.

Related JSON validation and formatting tools

Use these tools alongside validation to improve data quality and build a more reliable JSON workflow.

Format JSON

Format validated JSON for better readability, cleaner indentation, and easier review.

Repair JSON

Automatically fix common JSON syntax issues discovered during validation.

Compare JSON

Compare validated JSON files to find structural changes and track differences.

Schema Generator

Generate JSON Schema from validated JSON for future validation and documentation.

JSON to Table

Edit and inspect validated JSON in a visual table interface.

Frequently Asked Questions

What does this JSON validator check?

This validator checks whether your JSON is syntactically valid first, then adds structural statistics and risk hints. In addition to hard errors such as missing commas, unmatched brackets, and invalid escapes, it can also highlight potential issues like excessive nesting, unusually long strings, or suspicious structural patterns.

What kinds of JSON errors can it detect?

Common issues include missing commas, unclosed objects or arrays, malformed keys or strings, single quotes used instead of double quotes, trailing commas, invalid comments, and broken escape sequences. The page tries to provide line and column information so you can jump directly to the problem.

What is the difference between warnings and errors?

Errors mean the JSON cannot be parsed correctly and must be fixed before you continue. Warnings mean the JSON may still parse, but it contains patterns that could cause trouble later, such as deep nesting, oversized payloads, or unusual field shapes.

What is included in the validation report?

The report includes the validation timestamp, whether the JSON is valid, lists of errors and warnings, and summary statistics such as object count, array count, maximum depth, key count, and character count. It works well for tickets, API debugging notes, and code review context.

What is the difference between JSON validation and JSON repair?

Validation is for finding and explaining what is wrong, with precise locations and diagnostics. Repair is for automatically fixing common syntax problems. Use the validator when you want clarity; use repair when the JSON is too broken to fix efficiently by hand.

Can it handle large JSON files?

Yes. Typical API responses, config files, log snapshots, and medium-to-large JSON payloads work well. Larger payloads may take longer to analyze, but everything still runs locally in the browser.

Is my JSON uploaded anywhere?

No. Validation, diagnostics, and report generation all happen locally in your browser, which makes this page suitable for internal data, config values, and sensitive log payloads.