How is JSON encoded in the generated Swift?

Toolpaper detects Content-Type: application/json and emits idiomatic URLSession JSON serialization (json= for requests, Response.json for Go, etc.).

Does it preserve Content-Type?

Yes. The Content-Type header is honored and matched against the body so serialization stays consistent.

Is anything uploaded?

No. Parsing and generation happen entirely in your browser.

Send JSON with cURL in Swift

Paste a curl command that sends JSON and get idiomatic Swift code. We pick the right serialization for URLSession and set the correct Content-Type.

Quick answer

To convert a cURL command to Swift, paste it into the Toolpaper workbench below. It parses the command in your browser and emits idiomatic Swift code — headers, query string, request body, authentication (Bearer, Basic, API key), and cookies are all wired up automatically. No data is uploaded; conversion is fully client-side.

Prefer a different target? See the full cURL to Swift reference, or jump to the same guide in JavaScript, Node.js, or Python.

InputcURL command

MethodPOST·Headers1·Body40 B· Chars 132

OutputApple · URLSession(async/await)

import Foundation

let session = URLSession.shared
var request = URLRequest(url: URL(string: "https://api.example.com/users")!)
request.httpMethod = "POST"
request.setValue("application/json", forHTTPHeaderField: "Content-Type")
request.httpBody = "{\"name\":\"Ada\",\"email\":\"ada@example.com\"}".data(using: .utf8)

let (data, response) = try await session.data(for: request)
print(String(data: data, encoding: .utf8) ?? "")
// Note: to disable redirects, implement URLSessionTaskDelegate.urlSession(_:task:willPerformHTTPRedirection:...) and return nil.

Inspect

Example

A representative curl command for this scenario. Paste your own above to convert an exact match.

curl input

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

Implementation notes

Content-Type is detected from -H headers first, then inferred from the body shape when the header is missing.
JSON bodies are parsed and re-emitted through URLSession's serializer so quoting stays consistent with what the server expects.
Charset directives on Content-Type (e.g. application/json; charset=utf-8) survive the round trip.

Common mistakes

Setting Content-Type manually and then also using URLSession's helper — you end up with duplicate headers or the wrong one wins.
Mixing form encoding with JSON headers — the server rejects with 400 and it's easy to miss in code review.
Trusting the browser DevTools "Copy as cURL" to preserve charset — it often drops it. Clean panel restores common defaults.

Common questions

How is JSON encoded in the generated Swift?: Toolpaper detects Content-Type: application/json and emits idiomatic URLSession JSON serialization (json= for requests, Response.json for Go, etc.).
Does it preserve Content-Type?: Yes. The Content-Type header is honored and matched against the body so serialization stays consistent.
Is anything uploaded?: No. Parsing and generation happen entirely in your browser.

More payload types in Swift

Swift hub →

form-urlencoded in Swift

/how-to/send-form-with-curl-in-swift

multipart form-data in Swift

/how-to/send-multipart-with-curl-in-swift

XML in Swift

/how-to/send-xml-with-curl-in-swift

GraphQL in Swift

/how-to/send-graphql-with-curl-in-swift

The same guide in other languages

All guides →

In JavaScript

/how-to/send-json-with-curl-in-javascript

In Node.js

/how-to/send-json-with-curl-in-node

In Python

/how-to/send-json-with-curl-in-python

In Go

/how-to/send-json-with-curl-in-go

In PHP

/how-to/send-json-with-curl-in-php

In Ruby

/how-to/send-json-with-curl-in-ruby

In Rust

/how-to/send-json-with-curl-in-rust

In Java

/how-to/send-json-with-curl-in-java

Full Swift reference on the cURL to Swift hub, or open the main converter for all 18 targets.