webwrite — Write data to web services via HTTP and return decoded responses with MATLAB-compatible behavior.

webwrite sends request payloads to HTTP/HTTPS endpoints using methods like POST/PUT/PATCH/DELETE and decodes responses using MATLAB-compatible weboptions conventions.

Syntax

response = webwrite(url, data)
response = webwrite(url, data, optionsStruct)
response = webwrite(url, data, name, value, ...)
response = webwrite(url, data, optionsStruct, name, value, ...)

Inputs

Returns

Errors

How webwrite works

• The first input is an absolute URL supplied as a character vector or string scalar.
• The second input supplies the request body. Structs and two-column cell arrays become application/x-www-form-urlencoded payloads. Character vectors / strings are sent as UTF-8 text, and other MATLAB values default to JSON encoding via jsonencode.
• Name-value arguments (or an options struct) accept the same fields as MATLAB weboptions: ContentType, MediaType, Timeout, HeaderFields, Username, Password, UserAgent, RequestMethod, and QueryParameters.
• ContentType controls how the response is parsed ("auto" by default). Set it to "json", "text", or "binary" to force JSON decoding, text return, or raw byte vectors.
• MediaType sets the outbound Content-Type header. When omitted, RunMat chooses a sensible default (application/x-www-form-urlencoded, application/json, text/plain; charset=utf-8, or application/octet-stream) based on the payload.
• Query parameters can be appended through the QueryParameters option or by including additional, unrecognised name-value pairs. Parameter values follow MATLAB scalar rules.
• HTTP errors, timeouts, TLS verification problems, and JSON encoding issues raise MATLAB-style errors with descriptive text.

Does RunMat run webwrite on the GPU?

webwrite is a sink in the execution graph. Any GPU-resident inputs (for example tensors inside structs or cell arrays) are gathered to host memory before encoding the request body. Network I/O always runs on the CPU; fusion plans are terminated with ResidencyPolicy::GatherImmediately.

GPU memory and residency

No. webwrite executes on the CPU. Any GPU values are automatically gathered before serialising the payload, and results are created on the host. Manually gathering is unnecessary.

Examples

Posting form fields to a REST endpoint

payload = struct("name", "Ada", "score", 42);
opts = struct("ContentType", "json");          % expect JSON response
reply = webwrite("https://api.example.com/submit", payload, opts);
disp(reply.status)

Expected output:

"ok"

Sending JSON payloads

body = struct("title", "RunMat", "stars", 5);
opts = struct("MediaType", "application/json", "ContentType", "json");
resp = webwrite("https://api.example.com/projects", body, opts)

Uploading plain text

message = "Hello from RunMat!";
reply = webwrite("https://api.example.com/echo", message, ...
                 "MediaType", "text/plain", "ContentType", "text")

Uploading raw binary data

bytes = uint8([1 2 3 4 5]);
webwrite("https://api.example.com/upload", bytes, ...
         "ContentType", "binary", "MediaType", "application/octet-stream")

Supplying credentials, custom headers, and query parameters

headers = struct("X-Client", "RunMat", "Accept", "application/json");
opts = struct("Username", "ada", "Password", "lovelace", ...
              "HeaderFields", headers, ...
              "QueryParameters", struct("verbose", true));
profile = webwrite("https://api.example.com/me", struct(), opts)

Using webwrite with coding agents

Open a RunMat example with live inputs, then ask the agent to explain how webwrite changes the result.

FAQ

Related Io functions

Open-source implementation

Unlike proprietary runtimes, every RunMat function is open-source. Read exactly how webwrite is executed, line by line, in Rust.

• View the source for webwrite in Rust on GitHub
• Learn how the RunMat runtime works
• Found a bug? Open an issue with a minimal reproduction.

About RunMat

RunMat is an open-source runtime that executes MATLAB-syntax code blazing on any GPU. It is licensed under the Apache 2.0 license.

• RunMat automatically optimizes your math for GPU execution on Apple, Nvidia, and AMD hardware. No code changes needed. Simulations that took hours now take minutes.
• Start running code in seconds. RunMat runs in the browser, on the desktop, or from the CLI. No license server, no IT ticket.

Getting started · Benchmarks · Pricing