The Missing Voice in JSON: Why It Doesn't Allow Comments

I made this mistake thousands of times and I made it again today: trying to add comments to a JSON file. Though an easily fixable problem, it did intrigue me to wonder why JSON doesn't allow comments. In the world of programming and data interchange, JSON (JavaScript Object Notation) has become the lingua franca for storing and exchanging structured data. Its simplicity, ease of use, and compatibility with multiple programming languages have made it the go-to choice for web developers and data engineers alike. However, there's one aspect of JSON that has puzzled many developers, leading them to make the same mistake repeatedly: it doesn't allow comments.

Comments, those little notes added within code or data files to provide explanations, context, or reminders, are a fundamental feature of most programming languages and data formats. They serve as a form of documentation for both the developer and anyone else who might need to work with the code or data in the future. So, why does JSON choose to omit them?

A little reading on JSON history revealed some of the reasons.

One of the core principles behind JSON's design is simplicity. JSON was conceived as a lightweight data interchange format, primarily to support data transmission between a web server and a web client (browser). This simplicity has several benefits:

JSON's simple and regular structure makes it easy to parse, even for machines with limited computational resources. This predictability is crucial for web browsers, which need to process JSON data quickly to render web pages efficiently.

JSON is designed to be easily readable by humans, which encourages manual inspection and debugging. This feature is particularly useful when developers need to troubleshoot issues during development or when sharing data structures with colleagues.

JSON is programming language-agnostic, meaning it can be used with a wide range of programming languages without requiring complex language-specific parsers. This interoperability is a significant advantage for web developers working in diverse tech stacks.

Comments can be written in various ways, such as using double slashes (//) for single-line comments or enclosing text within /* */ for multi-line comments. This diversity creates ambiguity in how comments should be treated during parsing.

Different programming languages have their own conventions for comments. Including comments in JSON might clash with these conventions, causing compatibility issues when integrating JSON with other languages or tools.

Incorporating comments in JSON could open the door to security vulnerabilities if comments contain executable code or malicious content. JSON's current design ensures that there are no hidden surprises in the data it represents.

In the world of programming, every design choice involves trade-offs. JSON's decision to omit comments in favor of simplicity and predictability has its merits, but it can also be frustrating for developers who are accustomed to commenting their code and data. Now I understand the rationale behind this design choice, I don't think I will make the same mistake again.