Streaming Guide ​
HTTPX supports incremental request uploads and incremental response reads on the HTTP/1.1 client path, direct-to-disk downloads, and finite SSE responses. The high-level Response is buffered up to maxResponseSize; use requestStream when a response body must be consumed in chunks.
Streaming Response Downloads ​
For large files, download directly to disk without loading the full payload into RAM:
var client = httpx.Client.init(allocator, io, .{});
defer client.deinit();
_ = try client.download(
"https://releases.example.com/large_archive.iso",
.{ .path = "large_archive.iso" },
);Incremental Response Reads ​
requestStream returns a ResponseStream with a read method. On the HTTP/1.1 transport the body is read from the socket as it arrives. HTTP/2 and HTTP/3 upper layers currently buffer the completed response before returning the stream.
var stream = try client.requestStream("https://example.com/export.csv", .{});
defer stream.deinit();
var buf: [16 * 1024]u8 = undefined;
while (true) {
const n = try stream.read(&buf);
if (n == 0) break;
try processChunk(buf[0..n]);
}For streaming uploads, set RequestOptions.bodySource to a BodySource; see Requests.
Server-Sent Events (SSE) ​
httpx.sse.Event.Writer serializes SSE event blocks. Return the encoded body with the text/event-stream content type:
fn eventsHandler(ctx: *httpx.router.Context) anyerror!httpx.router.Response {
var out = std.ArrayList(u8).empty;
var writer = httpx.sse.Event.Writer.init(ctx.allocator);
try writer.writeEvent(&out, &.{"Server started"}, "status", 1, null);
return .{
.status = 200,
.body = out.items,
.contentType = "text/event-stream; charset=utf-8",
.headers = &.{.{ .name = "Cache-Control", .value = "no-cache" }},
};
}The high-level server buffers each response body, so this form sends a finite batch of events. Long-lived SSE connections require a custom HTTP/1.1 connection loop built from the socket and protocol primitives; the router cannot keep a response open.