JSON Payload Generator
Generate valid JSON payloads by target byte size (1 KB to 10 MB or custom amounts) with realistic data structures for API, database, and performance testing.
How the JSON Size Generator Works
The JSON Size Generator creates valid, syntactically correct JSON data structures calibrated to match target byte sizes (such as 1 KB, 10 KB, 100 KB, 500 KB, 1 MB, 5 MB, 10 MB, or custom byte amounts). It is designed for testing API payload limits, database column constraints, cache memory limits, and network throughput without relying on external mock services.
Payload Shapes
- Realistic Mixed: Structured objects simulating real-world user accounts, timestamps, geographical coordinates, tags, status flags, and metadata.
- Record Array: Top-level array of structured product/inventory records with numeric prices, SKUs, and ratings.
- String Heavy: Document collection with multi-paragraph text articles, authors, headlines, and summaries.
- Deeply Nested: Hierarchical recursive tree structure with nested child nodes to test recursive parser depth limits.
Authoritative Binary Sizing
Binary standard sizing is used:
1 KB = 1,024 bytes1 MB = 1,048,576 bytes
Frequently Asked Questions
How does the JSON generator hit exact target byte sizes?+
The generator creates structured schema templates (users, items, documents, or nested tree nodes), calculates total serialized UTF-8 bytes in memory, and micro-calibrates string fields to hit the requested byte boundary without invalid padding.
Are generated payloads sent to or stored on any server?+
No. Generation runs completely in your browser's local JavaScript environment.
Can I generate custom sizes like 250 KB or 2.5 MB?+
Yes. Choose 'Custom size' in the Target Size dropdown, type your numeric size, and select your desired unit (Bytes, KB, or MB).
Where can I inspect and deeply analyze existing JSON payloads?+
Use the dedicated JSON Payload Analyzer tool to measure UTF-8 bytes, character counts, and structural metrics for any pasted or uploaded JSON.