cURL Command Builder

The cURL Command Builder turns a fiddly multi-flag command into a guided form. You pick the HTTP method, paste a URL, list headers and query parameters one per line, set a request body, and choose an authentication mode — and the tool writes the corresponding curl command for you. A terminal-style preview updates as you type, so you can see the command take shape before you copy it.

The tool runs entirely in the browser. It does not call the URL you enter and it does not store your headers, tokens, or body. You get a ready-to-run command that you can paste into a terminal, a CI step, a Makefile, a Postman import, or a bug report.

Why a visual builder beats hand-rolled cURL

How to Use the cURL Command Builder

1. Pick a method. GET reads, POST creates, PUT/PATCH update, DELETE removes, HEAD fetches headers only, and OPTIONS asks the server which methods are supported on a resource.
2. Enter the URL. A full URL such as https://api.example.com/v1/users is best. If you omit the scheme the builder normalizes it to https://.
3. List query parameters. One per line as key=value. Leave the value blank for flag-style params. The builder appends them after a ?.
4. List headers. One per line as Header-Name: value. The builder de-duplicates and auto-adds Content-Type for JSON, form, and XML bodies if you have not set one.
5. Choose a body type. Pick JSON to paste an object, Form for application/x-www-form-urlencoded fields, Multipart for file uploads (use name=@/path/to/file), Raw to send bytes as-is, or XML for SOAP and similar APIs.
6. Set auth. Basic for user:password, Bearer for OAuth and JWT tokens, API key as either a header (like X-API-Key) or a query parameter (like ?api_key=...).
7. Add flags. Toggle the most common cURL flags: follow redirects, request gzip, show response headers, verbose mode, silent mode, or skip TLS checks for local debugging.
8. Choose an output style. Multi-line with backslash continuations reads best in scripts; one-line is best for copy/paste; Windows CMD uses double quotes and doubled percent signs; PowerShell uses curl.exe so it does not collide with the PowerShell alias.
9. Copy & run. Click Copy command, paste into your terminal, and inspect the response.

Output styles explained

Multi-line (default) puts each flag on its own line with a trailing backslash. This is the format you want in documentation, blog posts, and shell scripts because it reads top-to-bottom.

curl \
  -X POST \
  -H 'Content-Type: application/json' \
  --data '{"name":"Jesse"}' \
  'https://api.example.com/v1/users'

One-line joins everything with spaces — perfect for one-off pastes into a terminal, log messages, or chat threads.

Windows CMD converts bash-style single quotes into double quotes (CMD does not parse single quotes) and escapes percent signs by doubling them, so the command runs verbatim from cmd.exe or a .bat file.

PowerShell calls curl.exe explicitly because in PowerShell curl is an alias for Invoke-WebRequest, which has a different argument syntax.

Quoting: single vs double quotes

On Linux and macOS bash, single quotes are safest because bash does not expand variables or backticks inside them. The builder converts a literal ' inside the value to the escape sequence '\'' so the surrounding single quotes still match.

Double quotes are right when you want bash to keep escape rules but tolerate quote characters that would otherwise be hard to escape. The builder escapes $, `, \\, and " inside double quotes so the value is transmitted unchanged.

Authentication patterns

Basic auth sends Authorization: Basic base64(user:password). The cURL flag -u user:password performs the encoding for you. Use HTTPS — basic auth on plain HTTP is trivially intercepted.

Bearer tokens (OAuth 2.0, JWT, GitHub personal access tokens) add Authorization: Bearer <token>. Treat the token like a password: rotate it if it leaks into a screenshot, a Slack message, or a CI log.

API keys can live in a header (X-API-Key, X-RapidAPI-Key) or a query parameter (?api_key=...). Header is usually safer because URLs are commonly logged by reverse proxies and the browser history.

Common HTTP methods in one place

• GET — read a resource. Should be safe and idempotent.
• POST — create a new resource, or submit data that does not fit GET semantics. Not idempotent.
• PUT — replace a resource at a known URL. Idempotent.
• PATCH — partial update. Use JSON Patch (RFC 6902) or merge patch (RFC 7396) depending on the API.
• DELETE — remove a resource. Idempotent.
• HEAD — like GET but the server returns only headers. Use it to test cache freshness or content length without downloading the body.
• OPTIONS — ask the server which methods are allowed and read CORS metadata.

Troubleshooting your generated command

• SSL certificate errors. Toggle --insecure only against trusted hosts or your own local servers. For production debugging, prefer pointing cURL at the correct CA bundle with --cacert.
• Empty response or hang. Run with -v verbose mode to see the TLS handshake and headers. A hung connect step usually means the server is unreachable; a hung transfer step means the server accepted the request but is slow.
• 415 Unsupported Media Type. The server expects a different Content-Type. The builder auto-adds the right value for JSON, form, and XML bodies if you have not set one.
• 401 vs 403. 401 means the credentials are missing or invalid (re-check Bearer token); 403 means they are valid but the user is not allowed (check scopes).
• 413 Payload Too Large. Some upstreams cap body size at 1–10 MB. Consider chunked upload endpoints or streaming.

Security and privacy notes

• The builder is client-side rendering. Nothing is sent to the URL you enter; the result is only the command text.
• Avoid pasting production tokens. If you must, treat the generated command as sensitive — do not commit it to a public repo, paste it into a chat with bots, or attach it to a public issue.
• Prefer environment variables in scripts: write -H 'Authorization: Bearer '"$TOKEN" instead of hard-coding the token. Single-quote then break to double-quote around the variable so bash expands it.

FAQ

Can I import a cURL command from Chrome DevTools?

This builder is the opposite direction — it generates cURL from a form. To go the other way, copy as cURL from DevTools and use a dedicated cURL parser tool.

Does the JSON body need to be pre-escaped?

No. Paste the JSON exactly as it should appear. The builder handles quoting so the body reaches the server unmodified.

What is the difference between -d and --data-urlencode?

-d sends the body bytes as-is. --data-urlencode percent-encodes each field, which is what a browser sends for an HTML form. The builder uses --data-urlencode for the Form body type and --data for JSON / raw / XML.

How do I upload a file?

Choose Multipart form-data and add a line like avatar=@/Users/jesse/photo.png. The @ tells cURL to read the file contents.

Why does cURL report “Argument list too long”?

The body is too big for the shell’s argv limit. Pass the body as a file instead with --data @body.json.

Does the tool support HTTP/2 and HTTP/3?

cURL itself supports both with --http2 and --http3 if your local cURL was compiled with the right libraries. You can add either flag manually to a generated command.