v151 · fetch · streams
textStream() for response/request/blob
textStream() reads a byte-stream body — a Response, a Request, or a Blob — as a ReadableStream of decoded strings, always UTF-8. It is exactly equivalent to piping the body through a TextDecoderStream yourself, minus the footgun of forgetting to.
at a glance
| Milestone listing | Chrome 151 — Enabled by default |
|---|---|
| Feature detail | Desktop 151, Android 151; status text “Proposed” (updated 2026-06-22); ship stage (intent 5) desktop_first 151 |
| Surface | Method on the Body mixin (Request, Response) and on Blob |
| Runtime feature | TextStreamMethod — status stable at trunk (crbug.com/514448226) |
| Standards body | WHATWG Fetch (Body mixin) and W3C FileAPI (Blob) |
| ChromeStatus | 5146752165478400 — textStream() for response/request/blob |
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;TypeErrorwhen 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();| Parameters | None. |
|---|---|
| Return value | A ReadableStream whose chunks are strings — the body's bytes decoded as UTF-8. |
| Exceptions | TypeError if the object is unusable (its body is non-null and already disturbed or locked) — Fetch Standard method steps, mirrored by the RaisesException binding. |
| Null body | If the body is null, returns a new, already-closed empty ReadableStream (no exception). |
| Encoding | Always UTF-8 — the decoder is set up “regardless of the presence or the value of a Content-Type header and regardless of the presence or the value of a charset parameter” (Fetch). FileAPI notes this differs from readAsText(), which accepts an encoding label — textStream() has no encoding option. |
| Side effect | For a non-null body, reading begins immediately: bodyUsed becomes true as soon as textStream() is called, and the object becomes single-use. For a null body, bodyUsed stays false and repeated calls each return a new, independently closed empty stream (WPT null-body tests). Blob has no bodyUsed at all — every call returns a fresh stream. |
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.
| Engine / runtime | Support | Notes |
|---|---|---|
| Chrome | 151 | All three interfaces (Response, Request, Blob) per BCD; matches the Chrome 151 milestone listing (Enabled by default); Chrome for Android and WebView (Android + iOS) are BCD mirrors |
| Edge | mirror | BCD mirrors Chrome's data |
| Firefox | Not supported | BCD version_added: false (Firefox for Android mirrors); vendor signal recorded on the ChromeStatus entry: No signal |
| Safari | Not supported | BCD version_added: false (Safari on iOS mirrors); the ChromeStatus entry records a Positive signal — a recorded signal, not an official WebKit standards position (a feature this small has none) |
| Node.js | 26.5.0 | BCD records version_added: 26.5.0 for all three interfaces |
| Deno | Unknown | No BCD entry as of 2026-07-26 |
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).
Source: BCD api/Response.json; BCD api/Request.json; BCD api/Blob.json; chromestatus.com/feature/5146752165478400Specifications
| Specification | Status |
|---|---|
| WHATWG Fetch — Body mixin: textStream() | Living Standard (normative); landed via whatwg/fetch PR #1862 (merged) |
| W3C FileAPI — Blob.textStream() | Working Draft (normative) |
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 — TextDecoderStream (the adjacent API this method is shorthand for; MDN has no
textStream()page of its own as of 2026-07-26) - Chrome Platform Showcase — textStream() for response/request/blob (also: response pipeline, feature detect)