What's the difference between -d and --data-urlencode?

-d sends the data as-is in the request body. --data-urlencode URL-encodes the data first (replacing spaces with +, special chars with %XX). For form posts (application/x-www-form-urlencoded), --data-urlencode is correct because spaces and = signs need encoding. For JSON bodies, -d is correct because JSON has its own encoding. The builder picks the right flag based on your content-type.

Why does my curl command fail in PowerShell?

Quote-escaping differs across shells. Single quotes work in bash/zsh but PowerShell treats them differently. PowerShell aliases “curl” to Invoke-WebRequest by default — different syntax entirely. Two fixes: (1) use real curl.exe (modern Windows ships it; just use `curl.exe ...` or full path). (2) Generate the command in PowerShell flavor, which uses the right quoting style. The builder offers shell-flavor selection.

How do I pass JSON as the body?

Three options: (1) -d '{`{"key":"value"}`}' — single quotes around JSON in bash/zsh. (2) --data-binary @file.json — read JSON from a file (avoids quote-escaping pain). (3) Use --data-raw '...' to ensure curl doesn't try to interpret the data. Always include `-H "Content-Type: application/json"` header so the server parses correctly.

How do I auth with a bearer token?

Add `-H "Authorization: Bearer YOUR_TOKEN_HERE"`. Don't use `-u` (that's basic auth — sends user:password Base64-encoded, different mechanism). For API keys in custom headers: `-H "X-API-Key: yourkey"`. Always treat tokens as secret — don't paste them in public bug reports or shared scripts. Use environment variables (`$TOKEN`) in shell scripts.

Can I follow redirects?

Yes, add `-L`. Without `-L`, curl returns the 3xx response without following. With `-L`, it follows up to 50 redirects (configurable with --max-redirs). For testing, sometimes you DON'T want to follow (you want to inspect the redirect chain) — leave -L off and you'll see each intermediate response.

How do I save the response to a file?

`-o filename` to save to a specific name; `-O` to save with the URL's filename. For large downloads, `-C -` resumes interrupted transfers. For verbose debugging, `-v` shows headers and connection details. Combine: `curl -v -o output.txt -L -H "Authorization: ..." https://api.example.com/data`. The builder generates these patterns for common use cases.

Developer Utilities · Free tool

cURL Command Builder

Build a complex cURL command with headers, auth, and a JSON body using a simple online form. Copy it for instant use, free and no signup.

Updated June 2026

MethodURL

Query params

None.

Headers

Basic auth userBasic auth password

curl command

curl -X GET \
  'https://api.example.com/users' \
  -H 'Content-Type: application/json'

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What it does

curl is the universal command-line HTTP client — created by Daniel Stenberg in 1996, shipped on virtually every Unix system, macOS, modern Windows, embedded in countless scripts and Docker images. Building curl commands by hand is error-prone because the flag system is dense (-X for method, -H for headers, -d for body, -u for basic auth, -G for GET-with-data, -k for skip-cert-check, --data-urlencode for URL encoding, -L for follow redirects, etc.) and quoting bugs are common across shells (bash, zsh, PowerShell, cmd all handle quotes differently). The builder produces correctly-quoted curl commands from a structured form, so you don't fight quote-escaping when copying to a terminal or CI script.

The builder accepts: URL, HTTP method (GET, POST, PUT, PATCH, DELETE, HEAD, OPTIONS), headers (key-value pairs — Authorization, Content-Type, Accept, custom), query parameters (auto-URL-encoded), request body (JSON, form-data, raw text, or file upload), authentication (basic auth user:password, bearer token, custom Authorization header), and options like timeout, follow-redirects, ignore-cert-errors, output to file. Output: a copy-pasteable curl command in your shell flavor (bash/zsh, PowerShell, cmd, or format-on-multiple-lines for readability).

Common use cases: testing API endpoints (most APIs have curl examples in their docs), one-off API calls before writing formal client code, sharing a debug command with teammates (curl is universal), embedding API calls in CI / cron scripts, troubleshooting webhooks (replay incoming webhooks via curl), and capturing requests from browser DevTools (Network tab → Right- click → Copy as cURL — the tool can also parse this format and let you tweak it). Beware: curl commands often contain sensitive data (auth tokens, API keys) — treat as secret, don't paste in public channels without redacting first.

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How to use it

Enter the URL.
Pick the HTTP method (GET, POST, etc.).
Add headers (Authorization, Content-Type, custom).
Add query parameters (auto-URL-encoded) and request body if needed.
Set authentication (basic auth or bearer token).
Pick shell flavor (bash, PowerShell, cmd) and copy the result.

When to use this tool

Testing API endpoints quickly without writing client code.
Reproducing browser-DevTools requests outside the browser.
Sharing debug requests with teammates (curl is universal across systems).
Embedding HTTP calls in CI / cron / shell scripts.
Webhook replay — capturing an incoming webhook and replaying via curl to test handlers.

When not to use it

Production application code — use a proper HTTP library (axios, fetch, requests, OkHttp) for real apps.
GraphQL — better tooling exists (GraphQL Playground, Apollo, Insomnia) than crafting curl by hand.
Long-running streaming requests (SSE, WebSocket) — curl can but it's painful; use dedicated tools.
When you need a GUI-friendly REST client — Postman, Insomnia, Bruno, Hoppscotch are better for exploratory API work.

Common use cases

Verifying a number or output before passing it on
Quick generation during a typical workday
Pre-decision sanity-check on inputs and outputs
Educational use — demonstrating the underlying concept

Frequently asked questions

What's the difference between -d and --data-urlencode?: -d sends the data as-is in the request body. --data-urlencode URL-encodes the data first (replacing spaces with +, special chars with %XX). For form posts (application/x-www-form-urlencoded), --data-urlencode is correct because spaces and = signs need encoding. For JSON bodies, -d is correct because JSON has its own encoding. The builder picks the right flag based on your content-type.
Why does my curl command fail in PowerShell?: Quote-escaping differs across shells. Single quotes work in bash/zsh but PowerShell treats them differently. PowerShell aliases “curl” to Invoke-WebRequest by default — different syntax entirely. Two fixes: (1) use real curl.exe (modern Windows ships it; just use `curl.exe ...` or full path). (2) Generate the command in PowerShell flavor, which uses the right quoting style. The builder offers shell-flavor selection.
How do I pass JSON as the body?: Three options: (1) -d '{`{"key":"value"}`}' — single quotes around JSON in bash/zsh. (2) --data-binary @file.json — read JSON from a file (avoids quote-escaping pain). (3) Use --data-raw '...' to ensure curl doesn't try to interpret the data. Always include `-H "Content-Type: application/json"` header so the server parses correctly.
How do I auth with a bearer token?: Add `-H "Authorization: Bearer YOUR_TOKEN_HERE"`. Don't use `-u` (that's basic auth — sends user:password Base64-encoded, different mechanism). For API keys in custom headers: `-H "X-API-Key: yourkey"`. Always treat tokens as secret — don't paste them in public bug reports or shared scripts. Use environment variables (`$TOKEN`) in shell scripts.
Can I follow redirects?: Yes, add `-L`. Without `-L`, curl returns the 3xx response without following. With `-L`, it follows up to 50 redirects (configurable with --max-redirs). For testing, sometimes you DON'T want to follow (you want to inspect the redirect chain) — leave -L off and you'll see each intermediate response.
How do I save the response to a file?: `-o filename` to save to a specific name; `-O` to save with the URL's filename. For large downloads, `-C -` resumes interrupted transfers. For verbose debugging, `-v` shows headers and connection details. Combine: `curl -v -o output.txt -L -H "Authorization: ..." https://api.example.com/data`. The builder generates these patterns for common use cases.

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