JSON
JSON test files generated in your browser
Generate JSON fixtures locally for API mocks, schema validation, encoding, nesting depth, and large-payload parser tests.
Verified . Generated JSON output is produced locally in the browser; strict parsing, top-level shape, and key counts are verified before API or schema tests.
Identify JSON files
- Magic signature
No magic bytes (plain text)- Registered MIME
application/json
JSON is UTF-8 text built from objects, arrays, strings, numbers, and literals. There is no binary header, so a leading BOM, trailing whitespace, or trailing content after the top-level value can change how strict parsers behave.
Choosing JSON
JSON is the default interchange format for web APIs and is parsed by every major language. Parsers still differ on duplicate keys, numbers beyond safe integer range, nesting depth, and trailing content.
Generate JSON against a known schema so failures point at the parser, not the fixture.
Test strict parsing separately from lenient parsing.
Check number precision and unicode handling before trusting round-trips.
Common test cases
- API mock responses
- Schema validation
- Parser depth and size limits
Invalid and boundary cases
- Duplicate keys in one object
- Numbers beyond safe integer range
- Deeply nested structures that exhaust parser recursion
JSON fixture matrix
This format is generated locally in the browser and does not receive a permanent SEO URL.
Open the local generator