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Query Parameters

0xShakhawat
Author
0xShakhawat
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Query Parameters
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In addition to the request method and URL, many APIs utilize query parameters to refine requests. Query parameters are key-value pairs that provide additional information to the server.

Query Parameter Syntax
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Query parameters are appended to the request URL’s path. They begin with a question mark (?) followed by key-value pairs in the format key=value. Multiple parameters are separated by ampersands (&).

Examples:

  • GET https://some-api.com/photos?orientation=landscape (Single parameter)
  • GET https://some-api.com/photos?orientation=landscape&size=500x400 (Multiple parameters)

Example: Google Search #

A Google search utilizes query parameters. The URL https://www.google.com/search?q=postman uses the parameter q=postman to specify the search term. The server then returns an HTML page with search results for “Postman.” Modifying the value of q changes the search query.

When to Use Query Parameters
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API documentation dictates when and how to use query parameters. They may be optional filters or required for request processing.

The Postman Library API v2 allows optional query parameters on GET /books requests to filter responses.

Filtering Books by Genre
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This example demonstrates filtering book results by genre.

  1. In the Postman Library API v2 collection, duplicate the “get books” request.
  2. Rename the duplicated request to “get fiction books.”
  3. In the “Params” tab, add a query parameter with the key genre and the value fiction. Postman automatically adds the question mark (?).
  4. Save and send the request.

The response should contain only books with the fiction genre. Experimenting with different genre values is encouraged.

Fintering Books

Using Multiple Query Parameters
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This example adds a second query parameter to filter for available books (not checked out).

  1. In the “get fiction books” request, add another query parameter in the “Params” tab with the key checkedOut and the value false.
  2. Save and send the request.

The response should contain only fiction books where the checkedOut property is false. This might return an empty array ([]) if no such books exist. Saving the request before proceeding is recommended.

Multiple Query Parameters