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+---
+name: Write a file incrementally
+---
+
+Bun provides an API for incrementally writing to a file. This is useful for writing large files, or for writing to a file over a long period of time.
+
+Call `.writer()` on a `BunFile` to retrieve a `FileSink` instance. This instance can be used to efficiently buffer data and periodically "flush" it to disk. You can write & flush many times.
+
+```ts
+const file = Bun.file("/path/to/file.txt");
+const writer = file.writer();
+
+writer.write("lorem");
+writer.write("ipsum");
+writer.write("dolor");
+
+writer.flush();
+
+// continue writing & flushing
+```
+
+---
+
+The `.write()` method can accept strings or binary data.
+
+```ts
+w.write("hello");
+w.write(Buffer.from("there"));
+w.write(new Uint8Array([0, 255, 128]));
+writer.flush();
+```
+
+---
+
+The `FileSink` will also auto-flush when its internal buffer is full. You can configure the buffer size with the `highWaterMark` option.
+
+```ts
+const file = Bun.file("/path/to/file.txt");
+const writer = file.writer({ highWaterMark: 1024 * 1024 }); // 1MB
+```
+
+---
+
+When you're done writing to the file, call `.end()` to auto-flush the buffer and close the file.
+
+```ts
+writer.end();
+```
+
+---
+
+Full documentation: [FileSink](/docs/api/file-io#incremental-writing-with-filesink).