Top 10 Most Used Curl Commands: A Complete Guide for Developers
In today's interconnected world, API testing and HTTP requests have become essential skills for developers. One of the most powerful command-line tools for these tasks is curl. Whether you're debugging an API, downloading files, or testing your web application, curl offers versatility that few other tools can match.
This guide covers the top 10 most commonly used curl commands that every developer should know, with practical examples and explanations to help you master this essential tool.
In today's interconnected world, API testing and HTTP requests have become essential skills for developers. One of the most powerful command-line tools for these tasks is curl. Whether you're debugging an API, downloading files, or testing your web application, curl offers versatility that few other tools can match.
This guide covers the top 10 most commonly used curl commands that every developer should know, with practical examples and explanations to help you master this essential tool.
In today's interconnected world, API testing and HTTP requests have become essential skills for developers. One of the most powerful command-line tools for these tasks is curl. Whether you're debugging an API, downloading files, or testing your web application, curl offers versatility that few other tools can match.
This guide covers the top 10 most commonly used curl commands that every developer should know, with practical examples and explanations to help you master this essential tool.
The simplest and most common use of curl is making a GET request to fetch data from a URL:
curl https://example.com
This command retrieves the HTML content of the specified website. By default, curl outputs the response body to your terminal.
Key options to enhance basic GET requests:
-i or --include: Includes HTTP headers in the output
-s or --silent: Makes curl silent, hiding the progress meter and error messages
Example with headers:
curl -i https://api.github.com
The simplest and most common use of curl is making a GET request to fetch data from a URL:
curl https://example.com
This command retrieves the HTML content of the specified website. By default, curl outputs the response body to your terminal.
Key options to enhance basic GET requests:
-i or --include: Includes HTTP headers in the output
-s or --silent: Makes curl silent, hiding the progress meter and error messages
Example with headers:
curl -i https://api.github.com
The simplest and most common use of curl is making a GET request to fetch data from a URL:
curl https://example.com
This command retrieves the HTML content of the specified website. By default, curl outputs the response body to your terminal.
Key options to enhance basic GET requests:
-i or --include: Includes HTTP headers in the output
-s or --silent: Makes curl silent, hiding the progress meter and error messages
Example with headers:
curl -i https://api.github.com
2. Downloading Files
Curl excels at downloading files from the internet with its simple yet powerful syntax:
curl -O https://example.com/file.zip
The -O option saves the file with its original filename in your current directory. For more control over the download:
curl -o custom_name.zip https://example.com/file.zip
When dealing with interrupted downloads, curl can resume where it left off:
curl -C - -O https://example.com/large-file.iso
The -C - option tells curl to automatically figure out where to resume the download from.
Curl excels at downloading files from the internet with its simple yet powerful syntax:
curl -O https://example.com/file.zip
The -O option saves the file with its original filename in your current directory. For more control over the download:
curl -o custom_name.zip https://example.com/file.zip
When dealing with interrupted downloads, curl can resume where it left off:
curl -C - -O https://example.com/large-file.iso
The -C - option tells curl to automatically figure out where to resume the download from.
Curl excels at downloading files from the internet with its simple yet powerful syntax:
curl -O https://example.com/file.zip
The -O option saves the file with its original filename in your current directory. For more control over the download:
curl -o custom_name.zip https://example.com/file.zip
When dealing with interrupted downloads, curl can resume where it left off:
curl -C - -O https://example.com/large-file.iso
The -C - option tells curl to automatically figure out where to resume the download from.
3. POST Requests
Sending data to web servers is another common curl task. To make a POST request with form data:
curl -X POST -d "name=John&email=john@example.com" https://example.com/submit
For JSON data, which is common in modern APIs:
curl -X POST \ -H "Content-Type: application/json" \ -d '{"name":"John","email":"john@example.com"}' \ https://api.example.com/users
JSON data can also be sent from a file, which is useful for complex payloads:
curl -X POST -H "Content-Type: application/json" -d @data.json https://api.example.com/users
Sending data to web servers is another common curl task. To make a POST request with form data:
curl -X POST -d "name=John&email=john@example.com" https://example.com/submit
For JSON data, which is common in modern APIs:
curl -X POST \ -H "Content-Type: application/json" \ -d '{"name":"John","email":"john@example.com"}' \ https://api.example.com/users
JSON data can also be sent from a file, which is useful for complex payloads:
curl -X POST -H "Content-Type: application/json" -d @data.json https://api.example.com/users
Sending data to web servers is another common curl task. To make a POST request with form data:
curl -X POST -d "name=John&email=john@example.com" https://example.com/submit
For JSON data, which is common in modern APIs:
curl -X POST \ -H "Content-Type: application/json" \ -d '{"name":"John","email":"john@example.com"}' \ https://api.example.com/users
JSON data can also be sent from a file, which is useful for complex payloads:
curl -X POST -H "Content-Type: application/json" -d @data.json https://api.example.com/users
4. Authentication
Many APIs require authentication. Curl supports various authentication methods, with basic auth being the simplest:
curl -u username:password https://api.example.com/secure
For bearer token authentication, commonly used in OAuth 2.0 flows:
curl -H "Authorization: Bearer YOUR_ACCESS_TOKEN" https://api.example.com/resources
This method is widely used when working with modern APIs from services like GitHub, Twitter, or your own secured endpoints.
Many APIs require authentication. Curl supports various authentication methods, with basic auth being the simplest:
curl -u username:password https://api.example.com/secure
For bearer token authentication, commonly used in OAuth 2.0 flows:
curl -H "Authorization: Bearer YOUR_ACCESS_TOKEN" https://api.example.com/resources
This method is widely used when working with modern APIs from services like GitHub, Twitter, or your own secured endpoints.
Many APIs require authentication. Curl supports various authentication methods, with basic auth being the simplest:
curl -u username:password https://api.example.com/secure
For bearer token authentication, commonly used in OAuth 2.0 flows:
curl -H "Authorization: Bearer YOUR_ACCESS_TOKEN" https://api.example.com/resources
This method is widely used when working with modern APIs from services like GitHub, Twitter, or your own secured endpoints.
5. Custom Headers
Setting HTTP headers is essential when working with APIs:
curl -H "User-Agent: MyApp/1.0" https://api.example.com
Multiple headers can be specified for more complex requests:
curl -H "Content-Type: application/json" \ -H "Accept: application/json" \ -H "Authorization: Bearer token123" \ https://api.example.com/data
Headers help you control how your request is processed and what format responses should be in.
Setting HTTP headers is essential when working with APIs:
curl -H "User-Agent: MyApp/1.0" https://api.example.com
Multiple headers can be specified for more complex requests:
curl -H "Content-Type: application/json" \ -H "Accept: application/json" \ -H "Authorization: Bearer token123" \ https://api.example.com/data
Headers help you control how your request is processed and what format responses should be in.
Setting HTTP headers is essential when working with APIs:
curl -H "User-Agent: MyApp/1.0" https://api.example.com
Multiple headers can be specified for more complex requests:
curl -H "Content-Type: application/json" \ -H "Accept: application/json" \ -H "Authorization: Bearer token123" \ https://api.example.com/data
Headers help you control how your request is processed and what format responses should be in.
6. Follow Redirects
Many websites use redirects. By default, curl doesn't follow them, but you can enable this behavior:
curl -L https://shortened-url.com
The -L option makes curl follow redirects automatically. You can also limit the number of redirects:
curl -L --max-redirs 3 https://example.com
This prevents curl from following endless redirect loops, which can happen with misconfigured websites.
Many websites use redirects. By default, curl doesn't follow them, but you can enable this behavior:
curl -L https://shortened-url.com
The -L option makes curl follow redirects automatically. You can also limit the number of redirects:
curl -L --max-redirs 3 https://example.com
This prevents curl from following endless redirect loops, which can happen with misconfigured websites.
Many websites use redirects. By default, curl doesn't follow them, but you can enable this behavior:
curl -L https://shortened-url.com
The -L option makes curl follow redirects automatically. You can also limit the number of redirects:
curl -L --max-redirs 3 https://example.com
This prevents curl from following endless redirect loops, which can happen with misconfigured websites.
7. Verbose Output
When troubleshooting API calls or understanding how a website responds, verbose mode is invaluable:
curl -v https://api.example.com
For even more detailed information, especially about SSL/TLS handshakes:
curl --trace output.txt https://api.example.com
The verbose output shows:
Request headers sent by curl
Response headers received from the server
SSL/TLS negotiation details
Data transfers
This information is crucial when debugging connection issues or API problems.
When troubleshooting API calls or understanding how a website responds, verbose mode is invaluable:
curl -v https://api.example.com
For even more detailed information, especially about SSL/TLS handshakes:
curl --trace output.txt https://api.example.com
The verbose output shows:
Request headers sent by curl
Response headers received from the server
SSL/TLS negotiation details
Data transfers
This information is crucial when debugging connection issues or API problems.
When troubleshooting API calls or understanding how a website responds, verbose mode is invaluable:
curl -v https://api.example.com
For even more detailed information, especially about SSL/TLS handshakes:
curl --trace output.txt https://api.example.com
The verbose output shows:
Request headers sent by curl
Response headers received from the server
SSL/TLS negotiation details
Data transfers
This information is crucial when debugging connection issues or API problems.
8. Request Timeouts
When working with potentially slow servers, setting timeouts prevents your script from hanging indefinitely:
curl --connect-timeout 10 https://slow-server.com
You can also set a maximum time for the entire operation:
curl --max-time 30 https://slow-server.com/large-file
Setting appropriate timeouts is essential in automated scripts to handle network issues gracefully.
When working with potentially slow servers, setting timeouts prevents your script from hanging indefinitely:
curl --connect-timeout 10 https://slow-server.com
You can also set a maximum time for the entire operation:
curl --max-time 30 https://slow-server.com/large-file
Setting appropriate timeouts is essential in automated scripts to handle network issues gracefully.
When working with potentially slow servers, setting timeouts prevents your script from hanging indefinitely:
curl --connect-timeout 10 https://slow-server.com
You can also set a maximum time for the entire operation:
curl --max-time 30 https://slow-server.com/large-file
Setting appropriate timeouts is essential in automated scripts to handle network issues gracefully.
9. Using Proxy Servers
For testing or accessing region-restricted content, proxy support comes in handy:
curl -x http://proxy-server:8080 https://example.com
For SOCKS proxies, which are often used with SSH tunnels:
curl --socks5 localhost:1080 https://example.com
Proxies can help you test your applications from different geographic locations or bypass network restrictions.
For testing or accessing region-restricted content, proxy support comes in handy:
curl -x http://proxy-server:8080 https://example.com
For SOCKS proxies, which are often used with SSH tunnels:
curl --socks5 localhost:1080 https://example.com
Proxies can help you test your applications from different geographic locations or bypass network restrictions.
For testing or accessing region-restricted content, proxy support comes in handy:
curl -x http://proxy-server:8080 https://example.com
For SOCKS proxies, which are often used with SSH tunnels:
curl --socks5 localhost:1080 https://example.com
Proxies can help you test your applications from different geographic locations or bypass network restrictions.
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