Check JSON syntax, structure, and potential risks in real time. Includes error navigation, warnings, statistics, and exportable validation reports, all processed locally with no login required.
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.
無効な JSON（カンマ不足）
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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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}
検証結果
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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.
無効な JSON（カンマ不足）
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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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}
検証結果
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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.
無効な JSON（カンマ不足）
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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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}
検証結果
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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.
01
Tutorial Step
ステップ 1 – JSON を貼り付ける／インポートする
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.
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.
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Tutorial Step
ステップ 2 – 検証結果を確認する
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.
「エラー」一覧で、カンマ不足、括弧の閉じ忘れ、無効なエスケープなどのパースエラーを確認します。
「警告」では、深いネスト、非常に大きい文字列、不自然なパターンを確認します。
「統計」では、オブジェクト/配列数、最大深度、全体サイズを把握できます。
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.
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Tutorial Step
ステップ 3 – 修正して再検証する
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.
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.
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Tutorial Step
ステップ 4 – 検証レポートをエクスポートする
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.
「レポート」をクリックして、エラー、警告、統計を含む JSON レポートをダウンロードします。
デバッグ、コードレビュー、API 契約チェックのためにチームと共有できます。
レポートには行番号、メッセージ、概略の改善提案が含まれます。
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
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Paste the rawest version of the JSON into the validator instead of pre-editing it first.
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Read the errors, warnings, and statistics together so you understand both syntax failures and structural risk.
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Fix small issues in place, but switch to Repair JSON when the payload is heavily damaged or the error list is long.
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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.
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.
