Let Compress

Validate JSON

Check JSON syntax and review a formatted preview in your browser.

Browser-only processing: validation happens locally and your JSON is not uploaded.

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About JSON Validator

JSON Validator checks whether your JSON can be parsed correctly and helps you spot syntax issues faster. It is useful for APIs, config files, test payloads, and debugging. When the JSON is valid, you also get a formatted preview without sending data anywhere.For an upload limit stated in KB or MB, confirm the portal’s own rule and inspect the downloaded file size. Do not assume a percentage reduction meets that limit. Preserve the original if document text, signatures or forms must remain usable.

What should I check before downloading?

For an upload limit stated in KB or MB, confirm the portal’s own rule and inspect the downloaded file size. Do not assume a percentage reduction meets that limit. Preserve the original if document text, signatures or forms must remain usable.

  • Compare the downloaded file’s quality and actual size.
  • Savings vary by file. Some tools return the original if the output is larger; check the resulting format and size.
How to Validate JSON Online
  1. 1
    Paste your JSON

    Copy your JSON into the input editor.

  2. 2
    Run validation

    Check the JSON syntax in your browser and inspect any reported line or column details.

  3. 3
    Use the preview or fix the error

    If the JSON is valid, copy or download the formatted preview. If not, fix the reported syntax issue and validate again.

Frequently Asked Questions

What does JSON validation check?

It checks whether the JSON syntax is valid and can be parsed correctly by the browser.

Can this tool show line and column errors?

Yes. When the browser exposes the parsing location, the validator shows the related line and column details.

Does the validator also format valid JSON?

Yes. When the JSON is valid, the tool shows a formatted preview that you can copy or download.

Is validation done in the browser?

Yes. All validation is performed locally in your browser for privacy-first handling.

Why Choose Let Compress?
  • Compare the downloaded file’s quality and actual size.
  • Savings vary by file. Some tools return the original if the output is larger; check the resulting format and size.

References & Resources

Authoritative specifications and references for the file formats this tool works with.

RFC 8259 - The JSON Data Interchange Format

The IETF standard that defines JSON syntax.

ECMA-404 - The JSON Data Interchange Syntax

The Ecma standard that first specified JSON.

JSON.org

The original JSON resource site by Douglas Crockford.

Text processing tools for encoding, formatting, and transformation. Fast and free.