textStream() for response/request/blob

at a glance

Member reference

The feature adds exactly one method on three interfaces (the Body mixin covers Request and Response; Blob is defined separately in FileAPI). Each member has a stable detailed reference page covering syntax, inputs, outputs, errors, context, lifecycle, examples, compatibility, and security/privacy:

• Response.textStream() — read a response body as a stream of UTF-8 strings (single-use for non-null bodies; TypeError when unusable)
• Request.textStream() — read an upload payload as a stream of UTF-8 strings (consumes a non-null request body)
• Blob.textStream() — read a blob or file as a stream of UTF-8 strings (repeatable; each call creates a fresh stream)

Syntax

Defined on the Body interface mixin in the Fetch Standard, and separately on Blob in FileAPI:

// WHATWG Fetch — Body mixin (normative IDL)
ReadableStream textStream();

// W3C FileAPI — Blob (normative IDL)
ReadableStream textStream();

Chromium's bindings gate both behind the same runtime feature, marked stable:

// third_party/blink/renderer/core/fetch/body.idl
[RuntimeEnabled=TextStreamMethod, CallWith=ScriptState, RaisesException]
ReadableStream textStream();

// third_party/blink/renderer/core/fileapi/blob.idl
[RuntimeEnabled=TextStreamMethod, CallWith=ScriptState, NewObject, RaisesException]
ReadableStream textStream();

Local runtime check (headless Chrome 154.0.8037.97, 2026-10-08): Response, Request, and Blob each returned string chunks for "hello 世界". For non-null response/request bodies, bodyUsed was true immediately after textStream(); a second call threw TypeError, as did calling it while the original body stream was locked. Null response/request bodies each returned distinct closed streams (done: true) on repeat calls without setting bodyUsed. Two empty Blob calls likewise returned distinct closed streams. These observations match the cited specification and WPT contracts, not every possible error or deployment environment.

Examples

// Read a fetch() response as a stream of decoded text chunks.
const response = await fetch("/large-log.txt");
const reader = response.textStream().getReader();

while (true) {
  const { done, value } = await reader.read();
  if (done) break;
  console.log("chunk:", value); // value is a string, decoded as UTF-8
}

// Same contract on a Blob (e.g. a File from an <input type="file">):
const stream = file.textStream();
// ...and on a Request body before it is sent.

Browser compatibility

Per browser-compat-data (checked 2026-07-26): the entry exists for all three interfaces — api/Response.json, api/Request.json, and api/Blob.json.

Support rows are from BCD only. Separately, vendor signals come from the ChromeStatus API feature record (checked 2026-07-26): Firefox “No signal”, Safari “Positive”, web developers “No signals”. No Baseline entry: the webstatus.dev query returns no feature (checked 2026-07-26).

Specifications

See also

• whatwg/fetch PR #1862 — “Add a textStream() method to the Body mixin” (merged 2026-06-05; the feature's explainer, proposal, and spec change in one)
• WPT — fetch/api/body/textstream.any.js and WPT — FileAPI/blob/Blob-textStream.any.js
• crbug.com/514448226 — implementation tracking; Chromium runtime_enabled_features.json5 (TextStreamMethod, stable)
• Chromium body.idl; Chromium blob.idl
• MDN now has substantive Response.textStream(), Request.textStream(), and Blob.textStream() member pages (Specifications and Browser compatibility sections present, checked 2026-10-08). See also TextDecoderStream, the adjacent API this method is shorthand for.
• Chrome Platform Showcase — textStream() for response/request/blob (also: response pipeline, feature detect)