To test an API online, enter the endpoint URL, choose the HTTP method, add any headers or body, and click Send. The tool shows the response status, headers, and body.
API Tester sends HTTP requests (GET, POST, PUT, DELETE) to any endpoint and shows the response status, headers, and body. Like a lightweight Postman in your browser.
Last updated: 2026-04-12
✓ All processing happens in your browser✓ No sign-up required✓ 70 developer tools available✓ Built by developers, for developers
What is API Tester?
API Tester sends HTTP requests (GET, POST, PUT, DELETE) to any endpoint and shows the response status, headers, and body. Like a lightweight Postman in your browser.
Benefits of API Tester
Test APIs without installing software
Quick verification during development
Share request configurations with teammates
Debug CORS and authentication issues
Features
All HTTP methods supported
Custom headers and request body
Response status, headers, and body display
History of recent requests
JSON response formatting
Common use cases
Testing new API endpoints during development
Verifying authentication and authorization
Debugging production API responses
Checking CORS headers and preflight requests
Quick steps to use API Tester
Scroll to the workspace below—this same page loads the interactive tool.
Paste or type your input, then run the primary action.
Copy the output or switch tabs to another Developer Friend utility.
For long documents, combine with our JSON formatter, diff, or API tester as needed.
Detailed guide and reference: API Tester
How to Use API Tester
Enter the URL — Type or paste the API endpoint URL you want to test.
Configure the request — Choose the HTTP method (GET, POST, etc.), add headers, and optionally include a request body.
Send and inspect — Click Send to execute the request. Inspect the response status, headers, and body.
What is API Tester?
API Tester sends HTTP requests (GET, POST, PUT, DELETE) to any endpoint and shows the response status, headers, and body. Like a lightweight Postman in your browser.
As part of the API Tools collection on Developer Friend, this utility is designed to handle common api tasks that developers face daily. Whether you are debugging an API response, preparing test data, or converting between formats, API Tester provides a clean interface with instant results.
Why use API Tester online?
Quick API checks during development do not need a full desktop app. This tool loads instantly and works for one-off requests, debugging, and endpoint verification.
Browser-based tools eliminate the need to install desktop software, configure dependencies, or create accounts just to perform a quick operation. API Tester on Developer Friend loads in seconds and works entirely on your device — your data stays private, and the tool works even when you are offline after the first visit.
Compared to writing a one-off script, using a dedicated tool reduces the risk of edge-case errors and saves time. For teams, sharing a link to the tool is easier than sharing setup instructions for a local utility.
How to get started
Click the button above to open API Tester in the full Developer Friend workspace. Once there, you can paste your input, select options, and see results immediately. The workspace also lets you open multiple tools in tabs, switch between dark and light themes, and jump to related utilities in the sidebar.
For frequent use, bookmark the tool page or install Developer Friend as a PWA on your device. The entire suite is designed for speed — no loading spinners, no server round-trips for the core operations.
API Tester in your development workflow
Most developers use api tester as part of a larger debugging or data-preparation workflow. For example, you might format an API response with the JSON formatter, then use API Tester for the specific transformation you need, and finally verify the result with the appropriate validator.
Developer Friend is built to support this kind of multi-tool workflow. All tools share the same workspace, making it easy to switch between them. You can also use the Workflow Chains tool to automate multi-step transformations with a single click.
Privacy-friendly processing
Developer Friend runs utilities in your browser by default. Your input is not sent to our servers unless a tool explicitly performs a network request you initiate (for example, an API test or DNS lookup). This design makes these tools safer for internal payloads, authentication tokens, configuration secrets, and customer data during debugging sessions.
The tool uses no tracking pixels, no analytics cookies, and no third-party scripts that could access your input. For enterprise teams, this means no compliance concerns about data leaving the browser.
Example Usage
Here is a typical workflow with API Tester on Developer Friend:
1. Paste your input data into the tool
2. Select the desired operation or format
3. Click the action button to process
4. Copy the result to your clipboard
The tool handles common edge cases automatically, including special characters, Unicode text, and large inputs. For more complex workflows, combine API Tester with other Developer Friend tools using the tabbed workspace.
Key Features and Benefits
Key Features
All HTTP methods supported
Custom headers and request body
Response status, headers, and body display
History of recent requests
JSON response formatting
Benefits
Test APIs without installing software
Quick verification during development
Share request configurations with teammates
Debug CORS and authentication issues
Common Use Cases
Testing new API endpoints during development
Verifying authentication and authorization
Debugging production API responses
Checking CORS headers and preflight requests
Best Practices
Validate your input first — Make sure your data is well-formed before processing to avoid unexpected results.
Use keyboard shortcuts — Many Developer Friend tools support Ctrl+Enter to execute and Ctrl+Shift+C to copy output.
Combine tools for complex workflows — Use the tabbed workspace to chain multiple tools together for multi-step operations.
Bookmark frequently used tools — Save time by bookmarking direct links to the tools you use most often.
Keep sensitive data local — Avoid pasting production credentials into tools that make network requests; use client-side-only tools for sensitive data.
Common Mistakes to Avoid
Pasting incomplete data — Truncated input often causes parse errors. Make sure you copy the entire payload before pasting.
Confusing encoding with encryption — Encoding (Base64, URL, Hex) is reversible and not secure. Use proper encryption for sensitive data protection.
Ignoring character encoding — UTF-8 is the standard. If your input contains non-ASCII characters, ensure your source and target both expect UTF-8.
Not validating output — Always verify the result before using it in production. A quick check prevents cascading errors downstream.
How this compares to alternatives
Postman and Insomnia excel at collections, environments, and team sync. Developer Friend targets fast one-off requests and pairs with other tools in the same tab. For authenticated production calls, use your trusted API client and avoid logging secrets.
Frequently Asked Questions about API Tester
What is an API tester?
An API tester lets you send HTTP requests (GET, POST, PUT, DELETE) to endpoints and inspect the response status, headers, and body.
Is this like Postman?
Similar concept, but lighter—no install, no account. Great for quick API checks during development.
Can I send JSON request bodies?
Yes. Set the Content-Type header to application/json and write your JSON body in the request panel.
Is the API Tester on Developer Friend free?
Yes. API Tester and every other utility on Developer Friend are free to use in your browser. There is no sign-up wall and no paywall for core features.
Does my data leave my device when I use API Tester?
By default, API Tester runs entirely in your browser. Your input is not uploaded to Developer Friend servers unless the tool explicitly performs a network request you start (for example, an API test or DNS lookup).
Can I use API Tester offline?
After the first load, Developer Friend is cached by your browser and most tools work offline. Tools that need live network access still require a connection.
Who is Developer Friend for?
Developer Friend is built for software engineers, QA, DevOps, and technical writers who need fast formatters, encoders, and API helpers without installing desktop software.
How many tools are on Developer Friend?
Developer Friend offers 70+ free developer tools across JSON, API, encoding, time, Dev, and AI-assisted workflows.
Developer Friend is a free workspace with 70+ developer tools for JSON, APIs, encoding, time math, Dev utilities, and optional AI-assisted explainers. It is built for engineers who want fast answers in a browser tab without installing desktop software.
Privacy assurance
All processing happens in your browser for tools that do not initiate a network call. Sensitive payloads like JWTs, .env excerpts, and SQL drafts stay on your device unless you deliberately use a networked feature.
Why teams trust the platform
The interface is keyboard-friendly, theme-aware, and consistent across tools so you can move from formatting JSON to testing an API without relearning controls. There are no paywalls on core utilities and no sign-up requirement for day-to-day use.