API Query Builder & cURL Generator
Build API request URLs, configure query parameters and HTTP headers, and generate ready-to-use cURL commands with this free online API Query Builder. Prepare GET, POST, PUT, PATCH, and DELETE requests, add request bodies, and simplify API testing and debugging.
Build API URLs and Query Parameters
Enter a base API endpoint and add the query parameters required by your request. Define parameter names and values, add or remove parameters, and generate a URL with correctly encoded values. This helps you construct REST API URLs without manually concatenating strings or handling URL encoding yourself.
Configure HTTP Methods and Headers
Choose the HTTP method required by your endpoint, such as GET, POST, PUT, PATCH, or DELETE. Add custom HTTP headers, including Content-Type and Authorization, to reproduce the configuration expected by your API. This is useful when preparing authenticated requests or testing different API behaviors.
Generate Ready-to-Use cURL Commands
Convert your request configuration into a cURL command that can be copied into a terminal or shell script. The generated command brings together the request URL, HTTP method, query parameters, headers, and body. Use it to test endpoints, troubleshoot integrations, and share reproducible API requests with other developers.
Add a Request Body for POST, PUT, and PATCH
Provide a request body when an API endpoint expects data, for example when creating or updating a resource. Configure the payload alongside the HTTP method and headers, then include it in the generated cURL command. For JSON APIs, use an appropriate Content-Type header such as application/json.
API Query Builder & cURL Generator
Build HTTP requests visually, format query parameters, manage headers, and instantly generate cURL commands or code snippets for Fetch, Python, and Java.
| Key | Value | Action |
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| Header Name | Header Value | Action |
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All generation runs locally in your browser; requests are not sent. Query parameters are URL-encoded. cURL output targets POSIX-compatible shells; generated Java requires Java 11+. Avoid pasting real credentials into shared snippets.
FAQ
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What is an API Query Builder?
An API Query Builder helps you construct request URLs by combining a base endpoint with query parameters. It can also help configure HTTP methods and headers so you can prepare API requests without manually assembling every part of the URL. -
What is a cURL command used for?
cURL is a command-line tool used to send requests to URLs and interact with APIs. Developers commonly use it to test endpoints, inspect responses, troubleshoot integrations, and automate HTTP requests from scripts. -
Which HTTP methods can I use when building an API request?
Common HTTP methods include GET for retrieving data, POST for submitting or creating data, PUT for replacing a resource, PATCH for partially updating a resource, and DELETE for removing a resource. Select the method supported by the API endpoint you are calling. -
What are query parameters in an API URL?
Query parameters are key-value pairs appended to a URL after a question mark. Multiple parameters are generally separated by ampersands. They are often used to filter, sort, search, or otherwise customize the data returned by an API. -
How do I add authentication to an API request?
Authentication is often provided through an HTTP Authorization header, for example with a Bearer token. The exact header format depends on the API. Avoid placing real credentials in URLs or sharing generated commands that contain active secrets. -
Can I include a JSON request body in a cURL command?
Yes. For methods such as POST, PUT, and PATCH, a cURL command can include a JSON payload using the request body option. Set the Content-Type header to application/json when the API expects JSON data. -
Why should query parameter values be URL-encoded?
URL encoding ensures that special characters in parameter names or values are represented safely in a URL. Without encoding, characters such as spaces, ampersands, or question marks can be interpreted as URL syntax and change the meaning of the request. -
Does generating a cURL command guarantee that an API request will succeed?
No. The generated command only represents the request configuration. The request can still fail because of an incorrect endpoint, missing permissions, invalid credentials, unsupported methods, validation errors, network problems, or server-side issues.