API Request Builder - Build HTTP Requests & Generate Code

Construct a REST request with method, URL, query params, headers, auth, and body — then generate equivalent client code. Paste an existing cURL command to populate the builder.

What is an API Request Builder?

An API request builder is a form for HTTP: method, URL, query string, headers, authentication, and body. Instead of hand-writing the same call in five languages, you describe the request once and export snippets that match what you built.

That matters when you are switching contexts. A support engineer pastes a failing curl from a ticket. A frontend engineer wants fetch. A backend engineer wants requests or net/http. The request is the same; the syntax is not. A builder keeps the shared parts in one place and reduces copy-paste mistakes around escaping, Content-Type, and empty bodies.

This tool is intentionally narrower than a full API client. It does not execute the request against a remote host from CodeMirroring’s servers, store collections in the cloud, or sync environments. It helps you construct and translate requests locally.

How to Build an HTTP Request

Start with the method and URL. Most read paths are GET; creates use POST; full replacements use PUT; partial updates use PATCH; removals use DELETE. HEAD and OPTIONS are available when you need headers-only or CORS preflight inspection.

Add query parameters as discrete rows so you can enable or disable one field without rewriting the URL. The generator merges enabled rows into the final URL with correct encoding.

Headers follow the same pattern. Common ones:

• Accept: application/json
• Content-Type: application/json (set automatically for JSON bodies if you leave it blank)
• Authorization: Bearer … (or use the Authentication section so secrets are not duplicated)

Pick a body type only when the method needs one:

• JSON — validated before code generation; use Format JSON to pretty-print
• Form URL Encoded — application/x-www-form-urlencoded key/value pairs
• Multipart Form Data — text fields and file-name placeholders for uploads
• Raw Text — arbitrary payloads
• No Body — default for GET and HEAD

Use the request preview on the right to confirm the method line, headers (with sensitive values masked), and body before you copy code into a repo or a chat.

How to Generate cURL Commands

cURL is still the lingua franca of HTTP debugging. DevTools “Copy as cURL”, runbooks, and incident tickets all speak it. Choose cURL in the language dropdown, or use Export cURL, to get a multiline command with --request, --url, --header, and --data-raw / --form as needed.

Quotes and special characters are escaped for a POSIX shell. If your payload contains apostrophes, newlines, or Unicode, regenerate after edits instead of hand-patching the string — that is where most broken curls come from.

For the reverse direction — you already have cURL and want another language — paste into Import cURL, or use the dedicated cURL to Native Code tool when you specifically want Rust reqwest, Go net/http, C# HttpClient, Swift URLSession, or PowerShell.

How to Convert cURL to Code

Paste a command such as:

curl -X POST 'https://api.example.com/users?active=true' \
  -H 'Authorization: Bearer abc123' \
  -H 'Content-Type: application/json' \
  -d '{"name":"John","age":30}'

Import fills method, URL, query params, headers, bearer auth, and a pretty-printed JSON body. Then switch the language dropdown to JavaScript fetch, Axios, TypeScript, Python requests, Go, Java HttpClient, C#, PHP cURL, Ruby, or Rust.

Supported cURL pieces include -X / --request, -H / --header, -d / --data / --data-raw / --data-binary, --json, --url, -G, -u, -F form fields, and common no-op flags (-s, -L, --compressed). Flags that cannot be represented safely (proxies, client certs, write-out formats) produce a warning so you can review instead of getting a silently wrong request.

After import, skim the preview. If a file body (@payload.json) or an exotic flag was skipped, fix that field before shipping the snippet.

Supported Programming Languages

Generated code accounts for method, final URL (with query), headers, JSON vs form vs multipart vs raw bodies, and basic escaping. Multipart file fields use path placeholders — you still attach real files in your runtime. JSON bodies are pretty-printed in previews and validated before generation so you do not export a half-broken object literal.

Related helpers on this site:

• JSON Formatter / Validator — fix payloads before you paste them here
• JSON to Type Definitions — turn a sample response into TypeScript, Go, Rust, Pydantic, or Zod
• Base64 Encoder/Decoder — encode basic-auth or binary-ish header values
• JWT Decoder — inspect a bearer token you are about to put in Authorization

Is my API request data private?

Yes for this page’s processing model: everything runs in your browser. CodeMirroring does not upload your URL, headers, tokens, or body to build snippets. There is no “save to account” path that ships secrets to our servers, and the tool does not write your request into localStorage by default.

Still treat pasted credentials as live. Prefer short-lived tokens. Close the tab when you are done. Site analytics, when enabled in production, record only that a tool action was clicked (for example “generate” or “copy”) — not the contents of your fields. See also the privacy note under the builder.

If you need to scrub a log that already contains tokens before sharing it, use the Log Anonymizer.

API Request Builder vs Postman

Postman, Insomnia, and Hoppscotch are full API workspaces: collections, environments, history, mock servers, team sync. They shine when a team owns a large surface area and needs tests that run repeatedly.

This builder is for a different job:

• instant, no-install translation from a visual request (or pasted cURL) into copy-paste code
• zero account and zero sync of secrets
• SEO-friendly, shareable URL you can bookmark next to your other CodeMirroring tools

Use Postman when you are developing against an API for weeks. Use this page when you need a correct fetch or requests snippet in under a minute, or when someone dropped a multiline curl into Slack and you need it in Go before standup.

Tips for clean generated code

1. Prefer the Authentication section for Bearer / Basic / API keys so you do not maintain the same secret in two header rows.
2. Keep query parameters in the table, not hardcoded in the URL field — disabling a flag for a quick test is one checkbox.
3. Validate JSON before switching languages; invalid JSON blocks generation on purpose.
4. After importing cURL, open Request preview and confirm masked Authorization looks right.
5. For uploads, set Multipart fields to File and put the filename you will open in code; replace the placeholder with a real file handle in your project.

Build the request once. Copy the language you need. Keep the secrets in the tab, not on a server.