How to send binary data with cURL

Binary files such as images, executables, or arbitrary binary streams must remain unchanged during transfer. Unlike text data, binary content should not undergo encoding or line-ending modifications.

cURL accommodates binary uploads using --data-binary, ensuring a literal byte-for-byte transfer. Specifying the correct Content-Type further ensures proper server handling.

This approach supports file uploads, firmware transfers, or streaming arbitrary content without corruption. Validating server responses confirms that the binary data arrived intact and usable.

1. Open a terminal.
2. Use --data-binary to send raw binary content unmodified.

   $ curl --data-binary "@/path/to/binaryfile" "https://www.example.com/upload"

   The @ sign instructs cURL to read the file’s raw binary data.

3. Set the appropriate Content-Type header if required.

   $ curl --data-binary "@image.png" --header "Content-Type: image/png" "https://www.example.com/upload"

   Specifying MIME type ensures correct server-side handling.

4. Avoid --data for binary files to prevent unintended conversions.

   --data-binary preserves the original byte sequence.

5. Check the server’s response to confirm the file was received intact.

   Compare file sizes or use checksums to validate data integrity.