--- url: https://findutils.com/blog/curl-data-options-explained-d-data-raw-data-urlencode-form-json title: "curl -d vs --data-raw vs --data-urlencode vs -F vs --json: How curl Sends a Request Body" description: "What each curl body option really sends, measured: the Content-Type it adds, how @ and newlines are handled, how repeated -d joins, when -G moves data to the URL, and how to match it in fetch and Python requests." category: developer content_type: blog cluster: developer locale: en read_time: 9 status: published author: "olgunozoktas" published_at: 2026-10-25T15:08:00Z excerpt: "curl has six ways to send a body, and they differ in small ways that decide whether a server reads your data: -d adds a form Content-Type and strips newlines from files, --data-raw ignores @, --data-binary keeps every byte, --data-urlencode encodes the value, -F builds multipart, and --json sets two JSON headers. Here is what each one put on the wire in our tests, and how to send the same thing from fetch and Python." tag_ids: ["curl", "http", "api", "forms", "developer-tools"] tags: ["cURL", "HTTP", "API", "Forms", "Developer Tools"] primary_keyword: "curl data options" secondary_keywords: ["curl -d vs --data-raw", "curl --data-binary vs -d", "curl --data-urlencode example", "curl -F vs -d", "curl --json", "curl post form data", "curl -G query string"] tool_tag: "curl-to-code" related_tool: "curl-to-code" related_tools: ["curl-to-code", "url-encoder-decoder", "http-request-builder", "har-to-curl", "json-formatter", "postman-to-curl"] updated_at: "2026-10-25T15:08:00Z" og_image: "/images/content/blog/curl-data-options-explained-d-data-raw-data-urlencode-form-json-cover-20261025.webp" image_alt: "Six labelled lanes (-d, --data-raw, --data-binary, --data-urlencode, -F and --json) each carry a coloured square or round parcel, and their lines merge into one connector that runs into a server rack, on a dark background." --- curl sends a request body with six options, and they are not interchangeable. `-d` (`--data`) sends the text as `application/x-www-form-urlencoded`, reads a file when the value starts with `@`, and strips newlines from that file. `--data-raw` is the same but treats `@` as a normal character. `--data-binary` sends a file byte for byte. `--data-urlencode` percent-encodes the value first. `-F` (`--form`) builds a `multipart/form-data` body that can carry files. `--json` sends the data with `Content-Type: application/json` and `Accept: application/json`. All of them switch the method to POST unless you set another one, and `-G` moves `-d` data into the URL instead. We sent each option to a small local server that prints the raw request it receives, using curl 8.14.1. The results are below, followed by how to send the same body from JavaScript and Python. ## The Six Options at a Glance | Option | Content-Type curl adds | `@file` | Newlines from a file | Encodes the value | |---|---|---|---|---| | `-d`, `--data` | `application/x-www-form-urlencoded` | Reads the file | Removed | No | | `--data-raw` | `application/x-www-form-urlencoded` | Sent as text | (no file) | No | | `--data-binary` | `application/x-www-form-urlencoded` | Reads the file | Kept | No | | `--data-urlencode` | `application/x-www-form-urlencoded` | `name@file` reads and encodes | Kept, then encoded | Yes | | `-F`, `--form` | `multipart/form-data; boundary=...` | Attaches the file | Kept | No (each part is separate) | | `--json` (curl 7.82.0+) | `application/json`, plus `Accept: application/json` | Reads the file | Kept | No | Every one of them sets the method to POST. Adding `-X POST` changes nothing; `-X PUT` or `-X PATCH` keeps the same body and Content-Type with the other method. ## -d: The Form Default, Even for JSON ```bash curl https://api.example.com/login -d 'user=ada&role=admin' ``` arrived as: ```http POST /login HTTP/1.1 Content-Length: 19 Content-Type: application/x-www-form-urlencoded user=ada&role=admin ``` curl sends the text exactly as you typed it. It does not encode it: `-d 'name=Ada Lovelace'` arrived with the space still in it, which a strict form parser may reject. It also adds the form Content-Type to anything, including JSON. `curl https://api.example.com/x -d '{"a":1}'` arrived as `Content-Type: application/x-www-form-urlencoded` with a JSON body, so a JSON API that checks the header does not parse it. Add `-H 'Content-Type: application/json'`, or use `--json`. Two more rules from the curl manual, both confirmed in our tests: - **Repeated `-d` options are joined with `&`.** `-d user=ada -d role=admin` sent `user=ada&role=admin`. - **`-d @file` reads a file and removes carriage returns and newlines.** A file with `line1` and `line2` on two lines was sent as `line1line2` (10 bytes). That is fine for a one-line form body and breaks anything where line breaks matter, such as pretty-printed JSON with a string that spans lines, CSV or XML. ## --data-raw: When the Value Starts With @ `--data-raw` behaves like `-d` but never reads a file. `--data-raw '@notafile'` sent the 9 characters `@notafile`, where `-d '@notafile'` would look for a file of that name. Use it for bodies you did not write yourself, such as user input or a value that can start with `@` (a handle, an email-like string). It is also what Chrome and Firefox use when you choose **Copy as cURL** in the Network panel. ## --data-binary: Send a File Unchanged ```bash curl https://api.example.com/import --data-binary @body.txt ``` sent `line1\nline2\n` (12 bytes), newlines included. Use `--data-binary @file` for JSON, CSV, XML or any file whose bytes must arrive as they are. The Content-Type is still the form type, so set the real one: `-H 'Content-Type: text/csv'`, or `application/octet-stream` for arbitrary bytes, as the curl manual suggests. ## --data-urlencode: Let curl Encode the Value ```bash curl https://api.example.com/search \ --data-urlencode 'q=hello world & more' \ --data-urlencode 'lang=en' ``` sent `q=hello+world+%26+more&lang=en`. The value after the first `=` is encoded (the space became `+`, the `&` became `%26`), so a literal `&` no longer splits the field. The name before the `=` is not encoded, so keep names plain. The manual lists the other forms: `=content` encodes the content without a name, `name@file` encodes the contents of a file, and a value with no `=` or `@` is encoded as a whole. To see how a value is encoded before you send it, paste it into the [URL Encoder/Decoder](/network/url-encoder-decoder/); the post on [URL encoding and query strings](/blog/url-encoding-explained-percent-encoding-and-query-strings/) explains why a space can be `+` in a form and `%20` in a path. ## -F: Multipart, the Only One That Uploads Files ```bash curl https://api.example.com/upload -F name=Ada -F file=@body.txt ``` sent `Content-Type: multipart/form-data; boundary=...` and two parts: a field `name` with the value `Ada`, and a part with `filename="body.txt"` and `Content-Type: text/plain` holding the file. This is what an HTML form with a file input sends. Two details matter: - With `-F`, `@` attaches a file as an upload, while `<` puts the file's contents into a normal text field (`-F 'notes=