Convert curl to Swift

Q: What is Swift URLSession?

URLSession is Apple's built-in HTTP client for iOS, macOS, watchOS, and tvOS. It handles data tasks, downloads, uploads, WebSocket, and background transfers. No package installation needed — it's part of Foundation. Supports HTTP/2, caching, and cookie management. curl2code generates URLSession code for all Swift conversions.

Q: URLSession vs Alamofire — which should I use?

URLSession is built-in and covers most needs — use it to avoid third-party dependencies. Alamofire adds convenience: chainable request builders, automatic retry, response validation, and multipart uploads. For small projects, URLSession is sufficient. For similar built-in approaches, see our curl to Kotlin converter or curl to Objective-C.

Q: How to handle authentication in Swift?

Set the header on URLRequest: request.setValue("Bearer \(token)", forHTTPHeaderField: "Authorization"). For Basic auth, encode with Data("\(user):\(pass)".utf8).base64EncodedString(). curl2code converts -u and Bearer header flags to Swift code automatically.

Q: How to handle HTTP errors in Swift?

URLSession returns an optional Error in completions — check for nil. Cast the response to HTTPURLResponse and check statusCode. With async/await (iOS 15+), use try await URLSession.shared.data(for: request) in a do/catch block for clean error handling.

Q: How to use async/await with URLSession?

Swift 5.5+ supports async/await natively: let (data, response) = try await URLSession.shared.data(for: request). This replaces completion handler closures with linear code. Use Task { } to call from synchronous contexts. For concurrent requests, use async let or TaskGroup. For similar patterns, see curl to Dart.

Q: How to set timeouts in Swift URLSession?

Configure on URLSessionConfiguration: config.timeoutIntervalForRequest = 30 (per-request) and config.timeoutIntervalForResource = 300 (total). Or set request.timeoutInterval = 30 on individual requests. These map to curl's --max-time and --connect-timeout options.

Q: How to use a proxy with URLSession?

Set proxy on URLSessionConfiguration: config.connectionProxyDictionary = [kCFProxyHostNameKey: "proxy", kCFProxyPortNumberKey: 8080]. For SOCKS proxies, use kCFStreamPropertySOCKSProxy keys. URLSession also respects system-wide proxy settings configured in macOS/iOS settings.

Q: How to send a POST request with JSON body in Swift?

Convert a curl POST command like curl -X POST -H "Content-Type: application/json" -d "{"key":"value"}" URL to Swift using curl2code. The generated code uses request.httpBody = try JSONEncoder().encode(data). curl2code automatically detects -d/--data flags with JSON content and sets the appropriate Content-Type header in the URLSession code.

Q: How to add Bearer token authorization in Swift?

Pass curl -H "Authorization: Bearer YOUR_TOKEN" URL to curl2code and it generates URLSession code with the auth header: request.setValue("Bearer YOUR_TOKEN", forHTTPHeaderField: "Authorization"). curl2code detects Bearer tokens from both -H "Authorization: Bearer ..." and --oauth2-bearer flags. For Basic auth, use -u user:pass.

Convert curl commands to Swift code using URLSession. curl2code runs entirely in your browser via WebAssembly — your data stays private. For Kotlin (Android), try our curl to Kotlin converter. For Objective-C, see curl to Objective-C. Below are ready-to-use Swift examples.

How to copy curl from your browser

1
Open DevTools
Press F12 or Ctrl+Shift+I to open your browser developer tools.
2
Go to the Network tab
Click the Network tab and perform the action that triggers the HTTP request.
3
Copy as cURL
Right-click the request → Copy → Copy as cURL. Then paste it above.

Swift Code Examples

1Simple GET Request

curl command

curl https://api.example.com/users

Swift · URLSession

import Foundation

let url = URL(string: "https://api.example.com/users")!

var request = URLRequest(url: url)

let task = URLSession.shared.dataTask(with: request) { (data, response, error) in
    if let error = error {
        print(error)
    } else if let data = data {
        let str = String(data: data, encoding: .utf8)
        print(str ?? "")
    }
}

task.resume()

2POST with JSON Body

curl command

curl -X POST https://api.example.com/users \
  -H "Content-Type: application/json" \
  -d '{"name":"John","email":"john@example.com"}'

Swift · URLSession

import Foundation

let jsonData = [
    "name": "John",
    "email": "john@example.com"
] as [String : Any]
let data = try! JSONSerialization.data(withJSONObject: jsonData, options: [])

let url = URL(string: "https://api.example.com/users")!
let headers = [
    "Content-Type": "application/json"
]

var request = URLRequest(url: url)
request.httpMethod = "POST"
request.allHTTPHeaderFields = headers
request.httpBody = data as Data

let task = URLSession.shared.dataTask(with: request) { (data, response, error) in
    if let error = error {
        print(error)
    } else if let data = data {
        let str = String(data: data, encoding: .utf8)
        print(str ?? "")
    }
}

task.resume()

3Request with Bearer Token

curl command

curl https://api.example.com/me \
  -H "Authorization: Bearer token123"

Swift · URLSession

import Foundation

let url = URL(string: "https://api.example.com/me")!
let headers = [
    "Authorization": "Bearer token123"
]

var request = URLRequest(url: url)
request.allHTTPHeaderFields = headers

let task = URLSession.shared.dataTask(with: request) { (data, response, error) in
    if let error = error {
        print(error)
    } else if let data = data {
        let str = String(data: data, encoding: .utf8)
        print(str ?? "")
    }
}

task.resume()

4Multipart Form Upload

curl command

curl -X POST https://api.example.com/upload \
  -F "file=@document.pdf" \
  -F "description=My file"

Swift · URLSession

import Foundation

let url = URL(string: "https://api.example.com/upload")!

var request = URLRequest(url: url)
request.httpMethod = "POST"

let task = URLSession.shared.dataTask(with: request) { (data, response, error) in
    if let error = error {
        print(error)
    } else if let data = data {
        let str = String(data: data, encoding: .utf8)
        print(str ?? "")
    }
}

task.resume()

5Custom Headers

curl command

curl https://api.example.com/data \
  -H "X-API-Key: abc123" \
  -H "Accept: application/json" \
  -H "X-Request-ID: req-456"

Swift · URLSession

import Foundation

let url = URL(string: "https://api.example.com/data")!
let headers = [
    "X-API-Key": "abc123",
    "Accept": "application/json",
    "X-Request-ID": "req-456"
]

var request = URLRequest(url: url)
request.allHTTPHeaderFields = headers

let task = URLSession.shared.dataTask(with: request) { (data, response, error) in
    if let error = error {
        print(error)
    } else if let data = data {
        let str = String(data: data, encoding: .utf8)
        print(str ?? "")
    }
}

task.resume()

Frequently Asked Questions

What is Swift URLSession?

URLSession is Apple's built-in HTTP client for iOS, macOS, watchOS, and tvOS. It handles data tasks, downloads, uploads, WebSocket, and background transfers. No package installation needed — it's part of Foundation. Supports HTTP/2, caching, and cookie management. curl2code generates URLSession code for all Swift conversions.

URLSession vs Alamofire — which should I use?

URLSession is built-in and covers most needs — use it to avoid third-party dependencies. Alamofire adds convenience: chainable request builders, automatic retry, response validation, and multipart uploads. For small projects, URLSession is sufficient. For similar built-in approaches, see our curl to Kotlin converter or curl to Objective-C.

How to handle authentication in Swift?

Set the header on URLRequest: request.setValue("Bearer \(token)", forHTTPHeaderField: "Authorization"). For Basic auth, encode with Data("\(user):\(pass)".utf8).base64EncodedString(). curl2code converts -u and Bearer header flags to Swift code automatically.

How to send multipart form data in Swift?

Construct the multipart body manually: generate a boundary string, append each field/file with CRLF separators, and set Content-Type: multipart/form-data; boundary=.... For easier multipart, use Alamofire's upload(multipartFormData:). curl2code handles -F flag conversion for URLSession.

How to handle HTTP errors in Swift?

URLSession returns an optional Error in completions — check for nil. Cast the response to HTTPURLResponse and check statusCode. With async/await (iOS 15+), use try await URLSession.shared.data(for: request) in a do/catch block for clean error handling.

How to use async/await with URLSession?

Swift 5.5+ supports async/await natively: let (data, response) = try await URLSession.shared.data(for: request). This replaces completion handler closures with linear code. Use Task { } to call from synchronous contexts. For concurrent requests, use async let or TaskGroup. For similar patterns, see curl to Dart.

How to set timeouts in Swift URLSession?

Configure on URLSessionConfiguration: config.timeoutIntervalForRequest = 30 (per-request) and config.timeoutIntervalForResource = 300 (total). Or set request.timeoutInterval = 30 on individual requests. These map to curl's --max-time and --connect-timeout options.

How to use a proxy with URLSession?

Set proxy on URLSessionConfiguration: config.connectionProxyDictionary = [kCFProxyHostNameKey: "proxy", kCFProxyPortNumberKey: 8080]. For SOCKS proxies, use kCFStreamPropertySOCKSProxy keys. URLSession also respects system-wide proxy settings configured in macOS/iOS settings.

How to send a POST request with JSON body in Swift?

Convert a curl POST command like curl -X POST -H "Content-Type: application/json" -d "{"key":"value"}" URL to Swift using curl2code. The generated code uses request.httpBody = try JSONEncoder().encode(data). curl2code automatically detects -d/--data flags with JSON content and sets the appropriate Content-Type header in the URLSession code.

How to add Bearer token authorization in Swift?

Pass curl -H "Authorization: Bearer YOUR_TOKEN" URL to curl2code and it generates URLSession code with the auth header: request.setValue("Bearer YOUR_TOKEN", forHTTPHeaderField: "Authorization"). curl2code detects Bearer tokens from both -H "Authorization: Bearer ..." and --oauth2-bearer flags. For Basic auth, use -u user:pass.

How to set Content-Type header in Swift?

curl2code converts curl -H "Content-Type: application/json" URL to URLSession code with the proper header: request.setValue("application/json", forHTTPHeaderField: "Content-Type"). For -d data, curl defaults to application/x-www-form-urlencoded; for -F form uploads, it uses multipart/form-data. curl2code maps each to the correct URLSession API.

Useful Links

URLSession Documentation

developer.apple.com

Standard Library Reference

github.com

curl Man Page

curl.se

curl Guides

curl Error Codes

Look up any curl exit code — causes, fixes, and debugging tips.

Download Files with curl

Save files with -o, -O, follow redirects, resume downloads, and more.

SSL, TLS & Proxy

Configure certificates, TLS versions, HTTP/SOCKS proxies, and custom DNS.

How to copy curl from your browser

Swift Code Examples

1Simple GET Request

2POST with JSON Body

3Request with Bearer Token

4Multipart Form Upload

5Custom Headers

Frequently Asked Questions

Useful Links

curl Guides

Convert curl to Other Languages

Swift Code Examples

1Simple GET Request

2POST with JSON Body

3Request with Bearer Token

4Multipart Form Upload

5Custom Headers