JSON Validator
Validate JSON syntax and catch errors line by line
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Why does an API keep rejecting a payload that looks perfectly fine? Have you ever lost twenty minutes to a comma sitting one line too far down? JSON Validator reads your JSON, finds the syntax fault and tells you which line broke it.
Short answer: JSON Validator is a free tool on EizTools that checks JSON for syntax errors. Paste a payload and it reports unbalanced brackets, trailing commas, unquoted keys and bad escapes, naming the location and explaining the fix in plain language.
What is JSON Validator?
JSON Validator checks whether a block of JSON is well formed and explains anything that is not. JSON is unforgiving by design. One missing brace invalidates the whole document, and the parser error you get back usually points at the line where the failure was noticed rather than the line that caused it.
That gap is the real problem here. A parser says unexpected token at line 47. A reading of the structure says you opened an array at line 12 and never closed it.
How Does JSON Validator Work?
Paste the JSON into the prompt box. Everything after that is two clicks: an engine at the top, a settings panel below. The findings appear in the output card with a copy button, a TXT download for keeping the notes, and an activity history panel that holds each check from your session so a payload fixed in three rounds is still traceable.
A Worked Example
Take a small config that a service keeps rejecting:
{
"name": "reporting-job",
"retries": 3,
"targets": ["eu-west", "us-east",],
"enabled": true
}Set Output Type to Structured, Focus to Developers and Detail Level high. The report names the trailing comma after "us-east" as the fault, explains that JSON does not permit one before a closing bracket, and shows the corrected line. It also confirms the rest of the structure is sound, which is the part that saves you rereading it.
Key Features
| Option | Its effect on a JSON check | Suggested value |
|---|---|---|
| Output Type | How findings are laid out | Structured, giving one entry per fault |
| Focus / Audience | The technical register of the explanation | Developers, so the wording stays precise |
| Include Examples | Whether corrected JSON is shown alongside the fault | On, since the corrected line is the useful part |
| Detail Level | How much of the structure is described back | High for a payload you did not write yourself |
The panel behind this tool is the site's general purpose options set, so Tone, Length and the writing focused switches contribute little here. Custom Instructions carries the specifics, and it is where you say things like check this against the schema below, then paste the schema underneath your payload.
Caution Never paste a payload containing live API keys, access tokens or customer records. Replace the values with placeholders first. The structure is what is being checked, and dummy values check exactly as well as real ones.
What works well
- Explains the cause of a fault, not just the point where parsing stopped
- Returns corrected JSON you can paste straight back
- Handles a schema comparison when you supply the schema
- Reads deeply nested structures without you counting brackets by hand
What to watch for
- It reasons about the text rather than running a parser, so confirm the fix in your own tooling
- Very large payloads are better checked in sections
- The generic options panel needs setting deliberately for technical work
Common Mistakes
- Pasting a fragment rather than the whole object, which makes an unbalanced brace impossible to judge
- Leaving Focus on General, which produces an explanation aimed at a non technical reader
- Assuming valid JSON means correct JSON, when a well formed payload can still carry the wrong keys
When the payload is valid and the request still fails, the problem has moved into your code. The Error Fixer is the better tool for a stack trace, and the SQL Generator helps when the JSON is being built from a query that is returning the wrong shape.
Nothing on EizTools is rationed or charged for, which suits a debugging tool you might hit ten times in an hour. JSON Validator gives you a model selector as well, so a confusing payload can be read by a second AI family without changing anything else.
Frequently Asked Questions
Will it tell me which line the error is on?
Yes, and more usefully it names the line that caused the fault rather than the one where parsing failed. Those are frequently far apart in nested structures.
Can it check my JSON against a schema?
It can when you provide the schema. Paste the payload, then the schema underneath with a short label, and ask in Custom Instructions for a comparison of the two.
Does it format or minify JSON?
Ask for it in Custom Instructions and the corrected version comes back indented. Its main job is finding faults, but returning a readable copy is a reasonable extra request.
Is valid JSON the same as working JSON?
No. Valid means the syntax parses. An API can still reject it for missing a required field or using the wrong type, which is why a schema comparison is worth running too.
A JSON fault is a small problem with a bad ratio of frustration to cause. One character stops the whole document being readable, and the error rarely points at it. Paste the payload above with secrets stripped out, and get the line that actually broke it.
Sabir Bepari
Founder of EizTools and a passionate AI enthusiast dedicated to building practical, user-friendly AI tools that simplify everyday tasks.
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