Data Serialization
JSON vs JSON5: Differences That Matter In Real Projects
Compare JSON and JSON5, understand the syntax tradeoffs, and decide when strict JSON is the safer choice for tools, configs, and APIs.
Published: 2026-04-05 | Updated: 2026-04-05 | Read time: 9 minutes
Why JSON5 exists
JSON5 was designed to make human-authored configuration files easier to write. It adds conveniences like comments, trailing commas, and unquoted object keys, which can reduce friction in local config files.
Those conveniences are useful during editing, but they also make JSON5 less strict than standard JSON. That means a file can look valid to a developer while still being incompatible with systems that expect strict JSON.
When strict JSON is the better choice
Strict JSON is the safer choice for APIs, browser storage, and inter-service communication because every parser agrees on the same syntax rules. There is less ambiguity and fewer edge cases when the data moves between different runtimes.
If a payload must be consumed by tools outside your control, strict JSON prevents surprises. The receiver does not need a special parser, and the format stays compatible with standard validators everywhere.
How to choose between them
Use JSON5 when humans will edit the file often and the data stays inside a controlled developer workflow. Use strict JSON when the payload is exchanged between systems, sent over HTTP, or stored as a portable contract.
A practical rule is simple: if the file is meant to be read by software first, choose JSON. If it is meant to be written by humans first and parsed locally, JSON5 may be acceptable.