When Valid JSON Still Crashes at Runtime
TL;DR: A JSON validator only checks syntax. Most real-world bugs come from runtime expectations: duplicate keys, type mismatches, mixed arrays, or unexpected root shapes.
Common Runtime Pitfalls
- Duplicate keys where only the last value "wins".
- Boolean or numeric fields sent as strings.
- Arrays mixing numbers, strings, and objects in the same collection.
- Root-level arrays where the consumer expects an object.
- Large integers that exceed JavaScript's safe integer range.
Why Validators Don't Catch This
Syntax validators only ensure that the JSON text is structurally correct. They do not know how your app expects to consume the data, which is where most runtime failures come from.
Use JSON Runtime Checker for Real-World Issues
The JSON Runtime Checker focuses on the patterns that typically break deserialization and validation pipelines, surfacing them as breaking issues or risky patterns.
Analyze a Failing Payload
Paste your problematic payload into the JSON Runtime Checker to see which runtime patterns are likely causing the crash.