API Tester

Send HTTP requests to any API and inspect the response — status, headers, body and timing. Everything runs in your browser.

MockServer endpoint detected
KeyValue
KeyValue
Body is not valid JSON

            

            

                

                

                     Some headers may be hidden by CORS policy
                

            

            

                
            

        

    


    
    

    
    

        
        Send a request to see the response here
    


    
    

        






    


    
    

        

            

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What can you do with an online API tester?

        
An online API tester lets you send real HTTP requests — GET, POST, PUT, PATCH, DELETE — to any API endpoint and inspect the full response: status code, headers, body, and timing. Unlike desktop tools, it runs entirely in your browser with zero setup. Paste a URL, choose your method, add headers or a request body if needed, and hit Send. The response appears instantly with syntax-highlighted JSON, timing data, and the full header map.

        
Common use cases include testing REST APIs during development, verifying webhook payloads, debugging CORS issues, running quick smoke tests against staging endpoints, and following along with API tutorials. If the endpoint returns JSON (most modern APIs do), the Pretty view auto-formats it for easy reading.


        
How this compares to Postman, Insomnia, and cURL

        
    
            
  • Postman is a full-featured desktop app (and web app) with collections, environments, scripting, and team collaboration. It's the right tool for managing hundreds of API requests across a project. This tool is for the other 90% of the time — when you just need to fire one request and see what comes back.
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  • Insomnia is similar to Postman with a cleaner UI and GraphQL support. Same tradeoff — more power, more setup. This tool needs zero setup.
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  • cURL is the gold standard for CLI API testing. It bypasses CORS entirely (it's not a browser) and supports every HTTP feature. If you have a terminal open, curl is often faster. If you don't — or you want to see the response formatted and syntax-highlighted — this tool saves time. You can also import curl commands directly.
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Frequently asked questions

        

                        

                

                    
                

                

                    
An online API tester lets you send real HTTP requests to any URL and inspect the response — status code, headers, body and timing — directly in your browser. No software to install, no signup required.

                

            

                        

                

                    
                

                

                    
Yes. Add your API key, Bearer token, or Basic auth credentials in the Headers tab. Your credentials stay in your browser and are never sent to MockServer's servers.

                

            

                        

                

                    
                

                

                    
Browser-based tools are subject to CORS (Cross-Origin Resource Sharing) restrictions. If the target API doesn't include Access-Control-Allow-Origin headers, the browser blocks the response. Desktop tools like Postman and curl don't have this limitation. MockServer's Fake REST API and your own mock endpoints have CORS enabled by default.

                

            

                        

                

                    
                

                

                    
For quick, one-off API tests — yes. For managing collections, environments, team collaboration, and scripting — use Postman. This tool is designed for speed: paste a URL, hit Send, see the response. No account needed.

                

            

                        

                

                    
                

                

                    
No. Everything runs in your browser. Request history is saved in your browser's localStorage and is never sent to any server.

                

            

                    


        
Keyboard shortcuts

        

            Ctrl + Enter — Send request   
            Ctrl + L — Focus URL   
            Ctrl + Shift + C — Copy response   
            Ctrl + Shift + H — Toggle history
        


        

            Related tools:
            Fake REST API
            JSON Formatter
            JSON Validator
            Quick Mock
            All Tools
        

    








    

        
 Import cURL Command