GuidesHow to Validate JSON Online
How to Validate JSON Online
Updated 2026-07-23 · SparkJSON
Validating JSON online means checking that a string conforms to JSON grammar (RFC 8259). Paste into SparkJSON, run Format & Validate, and read line/column errors until you see Valid — without uploading your data.
Syntax validation vs schema validation
Syntax validation asks: is this parseable JSON? Schema validation asks: does this JSON match a contract (types, required fields, enums)? SparkJSON focuses on syntax plus duplicate-key warnings. Use JSON Schema or OpenAPI tools for contract checks.
How to validate with SparkJSON
Paste the payload and click Format & Validate. Invalid documents show a message such as “Trailing comma is not allowed” with a line and column. Fix that location and re-run until Valid appears.
Treat duplicate-key warnings seriously even when the document still parses: most engines keep only the last value and drop earlier ones.
Automate validation in CI
Online validators are for humans. In pipelines, use `jq empty`, language parsers, or schema validators so merges don’t introduce broken fixtures. SparkJSON remains the quick interactive check while developing.
FAQ
- Is pretty JSON always valid?
- No. Indentation can hide structural mistakes. Always run a real parse, not a visual check.
- Are comments allowed in JSON?
- No. Standard JSON forbids // and /* */ comments. Remove them or use JSONC only in tooling that explicitly supports it.