How to validate JSON data returned is valid?

Testing and validating JSON API is an important aspect of running a quality web service, but managing checks for large and diverse responders can be difficult. Using JSON schema to construct a model of your API response makes it easier to validate your API according to the valid JSON return type.

API consumption is on a high time everywhere from businessmen to personal projects, and they are constantly evolving to support the new features, bug fixing, and changing functionality to check valid JSON.

If you are tasked with testing your API code, you would realize the importance of having a Schema. It describes the data your application or service will accept and the data it will return. It is useful for automated testing and validating responded data.

What is JSON Schema?

JSON Schema is a vocabulary that allows you to interpret and validate JSON documents. It describes your existing data format with clear, human, and machine-readable documentation with complete structural validation. Online tools to check valid JSON are reliable to use when for cross-checking.

In modest terms, JSON schema is a contract for your JSON document that defines the expected data types and format of each field by checking valid JSON in the response. Naturally, you can recurse into each user and describe the format of its field as well.

JSON schema Validator to the rescue

JSON schema is very simple; point out which fields might exist, which are required or optional, what data format they use. Other validation rules can be added on top of that basic premise. There is an online JSON format validator too which you can use to check valid JSON.

The bit that probably needs explaining is the \$ schema key, which points to the draft version of JSON Schema in use. Knowing which draft you are validating against is important as different file validator cannot validate with other files. Luckily most JSON Schema tools keep up fairly well and are not madly changing stuff at random.

To try playing with this method, head over to to check valid JSON. For example, try removing the name field it will trigger an error as there is a required field syntax in there.

Triggering validation rules on random websites is one thing, but learning how to validate JSON string with code is going to be far more useful. For JavaScript, a module called ajv is fairly popular.

A validation () function is used to wrap the validation logic in a simple helper. Long URLs are not hardcoded they are being fetched from the response. Thus, any change in URL will automatically cause your valid JSON checker to fetch the new schema. Tools to check valid JSON allow your application to notice any errors or warnings automatically.

Dealing with Complex JSON Schema

In addition to defining the shape and data type of the JSON, you can also use things like ‘format’ to state a specific field that should match a regex. Additionally, there is support for things like examples and descriptions, which can be a great way to create a definition and documentation at the same time.

Here are primarily concerned with making sure the actual API response matches this schema. The next section will describe how to use Assertible to make this check.

JSON Schema assertions

There are many tools and libraries available to check valid JSON responses against a JSON Schema. Assertible has an easy-to-use JSON Schema assertion to validate an API response that we will set up in this example.

If you haven’t gotten started your journey with Assertible yet, you can create a free account and enter your API’s URL to get started.

The beauty of the JSON Schema assertion is that the schema can be as simple or complex, as thorough or as sparse, as you want. You may only want to check one or two fields, or you can check valid JSON data to validate the complete code.

Other tools you need to try

There are many other tools for working with JSON Schema, especially as programming language libraries. JSON Schema Test Suite is a great open-source project that contains a large list of JSON Schema parsers for almost every language.

The parsers can serve as a good starting point. On NPM, there are several widely used packages for working and checking valid JSON for each API endpoint, response, and field.

In the End

Validating your API responses against a JSON Schema is a very efficient way of ensuring your APIs are working as expected. Programming is a challenging job, and it requires a lot of attention and excellent knowledge of the language. The method of finding errors in a JSON is also a hard job as it requires a lot of time. That is why online JSON validators are here to help you to check valid JSON errors and save your time.

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