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  • One of the essential skills for a developer is to debug the application, API, or services and knowing the right tools is life-saver.

    What is Debugging?

    If you watch crime dramas, then the idea behind debugging will not be alien to you. Debugging is a process, and it involves a lot of tactics. It is the systematic finding and resolving problems and errors within a program.

    Besides, debugging sorts out all the issues that can prevent the correct operation of a software or, in this case, the web application. The process of debugging your API or web application primarily involves an attempt to reproduce the problem.

    Consequently, the need to send out an API request emerges. Now, this is where the problem lies. Most browsers will prevent you from changing the origin header, and even the limits on URL size.

    In other words, to reproduce the issue, you may need to perform some HTTP manipulations. And this will require some powerful debugging tools.

    All the components or tactics of  the debugging process includes;

    • Interactive debugging
    • Control flow analysis
    • Unit testing
    • Integration testing
    • Log file analysis
    • Monitoring
    • Memory Dumps
    • Profiling

    It is interesting to know that some HTTP clients, i.e., web browsers, have in-built web developer tools. These tools can be used to debug APIs. With this in mind, it is not necessary to write your debugging tool.

    What is HTTP Client?

    If you are thinking of building a system that leverages on the HTTP protocol for distributed communication, or one that is HTTP-aware, such as a web application. Then you may want to look at the HTTP client component.

    The HTTP, or HyperText Transfer Protocol, is the reason you can communicate, or transfer data, on the web, every time you type in a URL. It is an application protocol that makes browsing the internet possible.

    Now, the HTTP Client is a system that sends requests to a server, in HTTP text format, and in turn, receives a response from the same server.

    At this point, it is essential to know the differences between an HTTP client and the HTTP server.

    Differences Between HTTP Client and Server

    While the HTTP client is often web browsers, HTTP servers act as proxies to application servers. They serve as HTML, CSS, JS, PHP, Python, C#, Java, Node.js, among others.

    In simpler words, your smartphones, TVs, PlayStation, really any device that can connect to the internet, is probably using an HTTP Client.

    Similarly, the HTTP server is the network computer that the HTTP client connects to. The relationship they share is more of a conversational one. Where the HTTP client sends a request and the HTTP server responds.

    Examples of HTTP Requests

    Requests Outcomes
    GET Requests the entire resource
    HEAD Requests resource without the body
    POST Adds content to an existing web resource
    PUT Modifies an existing web resource
    DELETE Removes a specified resource
    TRACE Shows the changes to a web resource
    OPTIONS Shows available HTTP methods for the URL
    CONNECT Converts the request connection to a transparent TCP/IP tunnel
    PATCH Partially modifies a web resource

    Debugging APIs has never been easier. With these tools, you can finally relax while you do what you enjoy, web developing.

    First, let’s explore the command-line HTTP client.


    The ultimate aim of HTTPie is to make CLI interaction with web services user interface friendly. This tool provides an HTTP command for sending requests, all with the use of a natural syntax.

    Also, the HTTPie can be used for debugging, testing, and connecting with HTTP servers.


    • Built-in JSON support system
    • Documentation and plugins
    • Supports Linux, macOS, and Windows
    • Supports Python 2.7 and 3.x
    • Authenticate HTTPS and proxies
    • Intuitive syntax


    Requester is a robust client which combines the features of HTTPie, Postman, and Paw. It works only with Sublime Text editor.


    • Supports JSON Schemer
    • Request collections and history
    • Colorized output with syntax highlighting
    • Modern UX
    • Cookies, custom headers, request body, and query parameters are easy to set.
    • GraphQL support


    RESTer is available as an extension for Google Chrome and Firefox.


    • Authorization headers with Basic or Auth2 authentication
    • View request history
    • Perform requests with any method, URL, body and custom headers
    • Testing and debugging APIs


    Paw is an HTTP client, which allows you to send all kinds of HTTP requests. With Paw, you can test your APIs and also, explore new ones. Also, Paw has a full-featured visual editor and HTTP tool-set.

    Furthermore, Paw is exclusively built for macOS, and it has features that are easy to use. You can import and generate swagger, RAML, etc. and it supports JSON schema.


    Postman is unarguably one of the more popular HTTP clients used for debugging web applications. It allows for faster and easier API development.


    • Packs a powerful GUI, with a user-friendly interface.
    • History of requests.
    • Automated testing with collection runner.
    • Detailed API documentation.
    • Supports split-stack development.
    • Flexible API monitoring.

    In addition to all these great features, PostMan also supports a variety of payloads. Including JSON and HTML.


    NetTool is a free debugging tool. Unlike PostMan, it has two components; the TCP tunnel, and the HTTP client. Besides, NetTool can also be used to monitor a web application’s uptime, performance, and accuracy.

    Furthermore, NetTool can be used to manipulate an application’s level network messages.


    If you are more of a command line person, then cURL is the tool for you. cURL is a command line tool which is used for sending data, using URL syntax.

    cURL is useful when SSH into remote servers. It can also check and verify the certificate of those remote servers.


    • Supports a range of common network protocols.
    • Performs SSL certificate verification.
    • Included in nix distributions
    • Supports building scripts for testing and deployment.


    Fiddler is a cross-platform web application debugging proxy. It can edit and manipulate web sessions. Besides, Fiddler can decrypt HTTPS traffic and display web application requests.

    With Fiddler, you can compose your HTTP requests. Also, cookies, headers, and cache directives are transferred between the client and the server.


    • Web session manipulation
    • Performance testing
    • Security testing
    • HTTP/HTTPS traffic recording
    • Web debugging
    • Customization option

    Charles Proxy

    Charles proxy is also one of the most popular debugging tools. It is an HTTP proxy and works by routing your local machine traffic through it. Charles proxy can work on any smart device, and your PC, provided you configure it.

    You can use Charles for SSL proxying, bandwidth throttling, AJAX debugging, breakpoints and more.

    Second, using a web browser


    It is possible to debug your web application through your browser. The Firefox web browser allows you to add features, through the use of add-ons and extensions.

    So, you can use the web developer toolbar and other debugging extensions, right from your browser.

    Internet Explorer

    Although Internet Explorer may not be beneficial for more severe web APIs development, it can be run to check for crash reports.

    Also, it can check and detect errors and defective codes.


    The Safari browser web developer tool, by Apple, includes a web inspector. This tool makes it easy to debug, modify, monitor, and optimize a website application.

    Likewise, it has a user-friendly interface, the Responsive Design Mode. Here you can view your web pages, its resolutions, and orientations.


    Chrome developer tools are built directly in the browser. The DevTools can help to diagnose problems. Also, they allow you to edit pages on-the-fly.

    With Chrome developer tools, you can inspect your API in time and with less stress.


    Developing a web application or API can either be easy or not. Capturing the requests of an HTTP client and receiving a response from the HTTP server is no child’s play.

    However, with these tools, you can be on top of your game. Monitor your APIs, detect errors, and debug your web application, all these, and more, with the HTTP client.