diff --git a/packages/react-dom/src/server/ReactDOMServerFormatConfig.js b/packages/react-dom/src/server/ReactDOMServerFormatConfig.js
index b06196c452a6..37ee8feae309 100644
--- a/packages/react-dom/src/server/ReactDOMServerFormatConfig.js
+++ b/packages/react-dom/src/server/ReactDOMServerFormatConfig.js
@@ -7,11 +7,16 @@
  * @flow
  */
 
-import type {Destination} from 'react-server/src/ReactServerStreamConfig';
+import type {
+  Destination,
+  Chunk,
+  PrecomputedChunk,
+} from 'react-server/src/ReactServerStreamConfig';
 
 import {
   writeChunk,
-  convertStringToBuffer,
+  stringToChunk,
+  stringToPrecomputedChunk,
 } from 'react-server/src/ReactServerStreamConfig';
 
 import escapeTextForBrowser from './escapeTextForBrowser';
@@ -55,43 +60,43 @@ function encodeHTMLTextNode(text: string): string {
 }
 
 export function pushTextInstance(
-  target: Array<Uint8Array>,
+  target: Array<Chunk | PrecomputedChunk>,
   text: string,
 ): void {
-  target.push(convertStringToBuffer(encodeHTMLTextNode(text)));
+  target.push(stringToChunk(encodeHTMLTextNode(text)));
 }
 
-const startTag1 = convertStringToBuffer('<');
-const startTag2 = convertStringToBuffer('>');
+const startTag1 = stringToPrecomputedChunk('<');
+const startTag2 = stringToPrecomputedChunk('>');
 
 export function pushStartInstance(
-  target: Array<Uint8Array>,
+  target: Array<Chunk | PrecomputedChunk>,
   type: string,
   props: Object,
 ): void {
   // TODO: Figure out if it's self closing and everything else.
-  target.push(startTag1, convertStringToBuffer(type), startTag2);
+  target.push(startTag1, stringToChunk(type), startTag2);
 }
 
-const endTag1 = convertStringToBuffer('</');
-const endTag2 = convertStringToBuffer('>');
+const endTag1 = stringToPrecomputedChunk('</');
+const endTag2 = stringToPrecomputedChunk('>');
 
 export function pushEndInstance(
-  target: Array<Uint8Array>,
+  target: Array<Chunk | PrecomputedChunk>,
   type: string,
   props: Object,
 ): void {
   // TODO: Figure out if it was self closing.
-  target.push(endTag1, convertStringToBuffer(type), endTag2);
+  target.push(endTag1, stringToChunk(type), endTag2);
 }
 
 // Structural Nodes
 
 // A placeholder is a node inside a hidden partial tree that can be filled in later, but before
 // display. It's never visible to users.
-const placeholder1 = convertStringToBuffer('<span id="');
-const placeholder2 = convertStringToBuffer('P:');
-const placeholder3 = convertStringToBuffer('"></span>');
+const placeholder1 = stringToPrecomputedChunk('<span id="');
+const placeholder2 = stringToPrecomputedChunk('P:');
+const placeholder3 = stringToPrecomputedChunk('"></span>');
 export function writePlaceholder(
   destination: Destination,
   id: number,
@@ -101,16 +106,18 @@ export function writePlaceholder(
   writeChunk(destination, placeholder1);
   // TODO: Use the identifierPrefix option to make the prefix configurable.
   writeChunk(destination, placeholder2);
-  const formattedID = convertStringToBuffer(id.toString(16));
+  const formattedID = stringToChunk(id.toString(16));
   writeChunk(destination, formattedID);
   return writeChunk(destination, placeholder3);
 }
 
 // Suspense boundaries are encoded as comments.
-const startCompletedSuspenseBoundary = convertStringToBuffer('<!--$-->');
-const startPendingSuspenseBoundary = convertStringToBuffer('<!--$?-->');
-const startClientRenderedSuspenseBoundary = convertStringToBuffer('<!--$!-->');
-const endSuspenseBoundary = convertStringToBuffer('<!--/$-->');
+const startCompletedSuspenseBoundary = stringToPrecomputedChunk('<!--$-->');
+const startPendingSuspenseBoundary = stringToPrecomputedChunk('<!--$?-->');
+const startClientRenderedSuspenseBoundary = stringToPrecomputedChunk(
+  '<!--$!-->',
+);
+const endSuspenseBoundary = stringToPrecomputedChunk('<!--/$-->');
 
 export function writeStartCompletedSuspenseBoundary(
   destination: Destination,
@@ -134,10 +141,10 @@ export function writeEndSuspenseBoundary(destination: Destination): boolean {
   return writeChunk(destination, endSuspenseBoundary);
 }
 
-const startSegment = convertStringToBuffer('<div hidden id="');
-const startSegment2 = convertStringToBuffer('S:');
-const startSegment3 = convertStringToBuffer('">');
-const endSegment = convertStringToBuffer('"></div>');
+const startSegment = stringToPrecomputedChunk('<div hidden id="');
+const startSegment2 = stringToPrecomputedChunk('S:');
+const startSegment3 = stringToPrecomputedChunk('">');
+const endSegment = stringToPrecomputedChunk('"></div>');
 export function writeStartSegment(
   destination: Destination,
   id: number,
@@ -146,7 +153,7 @@ export function writeStartSegment(
   writeChunk(destination, startSegment);
   // TODO: Use the identifierPrefix option to make the prefix configurable.
   writeChunk(destination, startSegment2);
-  const formattedID = convertStringToBuffer(id.toString(16));
+  const formattedID = stringToChunk(id.toString(16));
   writeChunk(destination, formattedID);
   return writeChunk(destination, startSegment3);
 }
@@ -276,12 +283,14 @@ const completeBoundaryFunction =
 const clientRenderFunction =
   'function $RX(b){if(b=document.getElementById(b)){do b=b.previousSibling;while(8!==b.nodeType||"$?"!==b.data);b.data="$!";b._reactRetry&&b._reactRetry()}}';
 
-const completeSegmentScript1Full = convertStringToBuffer(
+const completeSegmentScript1Full = stringToPrecomputedChunk(
   '<script>' + completeSegmentFunction + ';$RS("S:',
 );
-const completeSegmentScript1Partial = convertStringToBuffer('<script>$RS("S:');
-const completeSegmentScript2 = convertStringToBuffer('","P:');
-const completeSegmentScript3 = convertStringToBuffer('")</script>');
+const completeSegmentScript1Partial = stringToPrecomputedChunk(
+  '<script>$RS("S:',
+);
+const completeSegmentScript2 = stringToPrecomputedChunk('","P:');
+const completeSegmentScript3 = stringToPrecomputedChunk('")</script>');
 
 export function writeCompletedSegmentInstruction(
   destination: Destination,
@@ -297,19 +306,21 @@ export function writeCompletedSegmentInstruction(
     writeChunk(destination, completeSegmentScript1Partial);
   }
   // TODO: Use the identifierPrefix option to make the prefix configurable.
-  const formattedID = convertStringToBuffer(contentSegmentID.toString(16));
+  const formattedID = stringToChunk(contentSegmentID.toString(16));
   writeChunk(destination, formattedID);
   writeChunk(destination, completeSegmentScript2);
   writeChunk(destination, formattedID);
   return writeChunk(destination, completeSegmentScript3);
 }
 
-const completeBoundaryScript1Full = convertStringToBuffer(
+const completeBoundaryScript1Full = stringToPrecomputedChunk(
   '<script>' + completeBoundaryFunction + ';$RC("',
 );
-const completeBoundaryScript1Partial = convertStringToBuffer('<script>$RC("');
-const completeBoundaryScript2 = convertStringToBuffer('","S:');
-const completeBoundaryScript3 = convertStringToBuffer('")</script>');
+const completeBoundaryScript1Partial = stringToPrecomputedChunk(
+  '<script>$RC("',
+);
+const completeBoundaryScript2 = stringToPrecomputedChunk('","S:');
+const completeBoundaryScript3 = stringToPrecomputedChunk('")</script>');
 
 export function writeCompletedBoundaryInstruction(
   destination: Destination,
@@ -330,23 +341,21 @@ export function writeCompletedBoundaryInstruction(
     boundaryID.id !== null,
     'An ID must have been assigned before we can complete the boundary.',
   );
-  const formattedBoundaryID = convertStringToBuffer(
+  const formattedBoundaryID = stringToChunk(
     encodeHTMLIDAttribute(boundaryID.id),
   );
-  const formattedContentID = convertStringToBuffer(
-    contentSegmentID.toString(16),
-  );
+  const formattedContentID = stringToChunk(contentSegmentID.toString(16));
   writeChunk(destination, formattedBoundaryID);
   writeChunk(destination, completeBoundaryScript2);
   writeChunk(destination, formattedContentID);
   return writeChunk(destination, completeBoundaryScript3);
 }
 
-const clientRenderScript1Full = convertStringToBuffer(
+const clientRenderScript1Full = stringToPrecomputedChunk(
   '<script>' + clientRenderFunction + ';$RX("',
 );
-const clientRenderScript1Partial = convertStringToBuffer('<script>$RX("');
-const clientRenderScript2 = convertStringToBuffer('")</script>');
+const clientRenderScript1Partial = stringToPrecomputedChunk('<script>$RX("');
+const clientRenderScript2 = stringToPrecomputedChunk('")</script>');
 
 export function writeClientRenderBoundaryInstruction(
   destination: Destination,
@@ -365,7 +374,7 @@ export function writeClientRenderBoundaryInstruction(
     boundaryID.id !== null,
     'An ID must have been assigned before we can complete the boundary.',
   );
-  const formattedBoundaryID = convertStringToBuffer(
+  const formattedBoundaryID = stringToPrecomputedChunk(
     encodeHTMLIDAttribute(boundaryID.id),
   );
   writeChunk(destination, formattedBoundaryID);
diff --git a/packages/react-native-renderer/src/server/ReactNativeServerFormatConfig.js b/packages/react-native-renderer/src/server/ReactNativeServerFormatConfig.js
index f4e58a03c7ef..d82488ab171c 100644
--- a/packages/react-native-renderer/src/server/ReactNativeServerFormatConfig.js
+++ b/packages/react-native-renderer/src/server/ReactNativeServerFormatConfig.js
@@ -7,11 +7,12 @@
  * @flow
  */
 
-import type {Destination} from 'react-server/src/ReactServerStreamConfig';
+import type {Destination, Chunk, PrecomputedChunk} from 'react-server/src/ReactServerStreamConfig';
 
 import {
   writeChunk,
-  convertStringToBuffer,
+  stringToChunk,
+  stringToPrecomputedChunk,
 } from 'react-server/src/ReactServerStreamConfig';
 
 import invariant from 'shared/invariant';
@@ -71,10 +72,10 @@ export function createSuspenseBoundaryID(
   return responseState.nextSuspenseID++;
 }
 
-const RAW_TEXT = convertStringToBuffer('RCTRawText');
+const RAW_TEXT = stringToPrecomputedChunk('RCTRawText');
 
 export function pushTextInstance(
-  target: Array<Uint8Array>,
+  target: Array<Chunk | PrecomputedChunk>,
   text: string,
 ): void {
   target.push(
@@ -87,20 +88,20 @@ export function pushTextInstance(
 }
 
 export function pushStartInstance(
-  target: Array<Uint8Array>,
+  target: Array<Chunk | PrecomputedChunk>,
   type: string,
   props: Object,
 ): void {
   target.push(
     INSTANCE,
-    convertStringToBuffer(type),
+    stringToChunk(type),
     END, // Null terminated type string
     // TODO: props
   );
 }
 
 export function pushEndInstance(
-  target: Array<Uint8Array>,
+  target: Array<Chunk | PrecomputedChunk>,
   type: string,
   props: Object,
 ): void {
diff --git a/packages/react-noop-renderer/src/ReactNoopFlightServer.js b/packages/react-noop-renderer/src/ReactNoopFlightServer.js
index 411e6094164c..7614ba3e8dfb 100644
--- a/packages/react-noop-renderer/src/ReactNoopFlightServer.js
+++ b/packages/react-noop-renderer/src/ReactNoopFlightServer.js
@@ -27,15 +27,18 @@ const ReactNoopFlightServer = ReactFlightServer({
     callback();
   },
   beginWriting(destination: Destination): void {},
-  writeChunk(destination: Destination, buffer: Uint8Array): void {
-    destination.push(Buffer.from((buffer: any)).toString('utf8'));
+  writeChunk(destination: Destination, chunk: string): void {
+    destination.push(chunk);
   },
   completeWriting(destination: Destination): void {},
   close(destination: Destination): void {},
   closeWithError(destination: Destination, error: mixed): void {},
   flushBuffered(destination: Destination): void {},
-  convertStringToBuffer(content: string): Uint8Array {
-    return Buffer.from(content, 'utf8');
+  stringToChunk(content: string): string {
+    return content;
+  },
+  stringToPrecomputedChunk(content: string): string {
+    return content;
   },
   isModuleReference(reference: Object): boolean {
     return reference.$$typeof === Symbol.for('react.module.reference');
diff --git a/packages/react-server/src/ReactFizzServer.js b/packages/react-server/src/ReactFizzServer.js
index 4f5879b86bff..4731e965dab2 100644
--- a/packages/react-server/src/ReactFizzServer.js
+++ b/packages/react-server/src/ReactFizzServer.js
@@ -8,7 +8,11 @@
  */
 
 import type {Dispatcher as DispatcherType} from 'react-reconciler/src/ReactInternalTypes';
-import type {Destination} from './ReactServerStreamConfig';
+import type {
+  Destination,
+  Chunk,
+  PrecomputedChunk,
+} from './ReactServerStreamConfig';
 import type {ReactNodeList} from 'shared/ReactTypes';
 import type {
   SuspenseBoundaryID,
@@ -78,7 +82,7 @@ type Segment = {
   parentFlushed: boolean, // typically a segment will be flushed by its parent, except if its parent was already flushed
   id: number, // starts as 0 and is lazily assigned if the parent flushes early
   +index: number, // the index within the parent's chunks or 0 at the root
-  +chunks: Array<Uint8Array>,
+  +chunks: Array<Chunk | PrecomputedChunk>,
   +children: Array<Segment>,
   // If this segment represents a fallback, this is the content that will replace that fallback.
   +boundary: null | SuspenseBoundary,
diff --git a/packages/react-server/src/ReactFlightServerConfigStream.js b/packages/react-server/src/ReactFlightServerConfigStream.js
index 12241493e57f..b9a57c16eb27 100644
--- a/packages/react-server/src/ReactFlightServerConfigStream.js
+++ b/packages/react-server/src/ReactFlightServerConfigStream.js
@@ -66,11 +66,11 @@ ByteSize
 
 import type {Request, ReactModel} from 'react-server/src/ReactFlightServer';
 
-import {convertStringToBuffer} from './ReactServerStreamConfig';
+import {stringToChunk} from './ReactServerStreamConfig';
 
-export type {Destination} from './ReactServerStreamConfig';
+import type {Chunk} from './ReactServerStreamConfig';
 
-export type Chunk = Uint8Array;
+export type {Destination, Chunk} from './ReactServerStreamConfig';
 
 const stringify = JSON.stringify;
 
@@ -86,7 +86,7 @@ export function processErrorChunk(
 ): Chunk {
   const errorInfo = {message, stack};
   const row = serializeRowHeader('E', id) + stringify(errorInfo) + '\n';
-  return convertStringToBuffer(row);
+  return stringToChunk(row);
 }
 
 export function processModelChunk(
@@ -96,7 +96,7 @@ export function processModelChunk(
 ): Chunk {
   const json = stringify(model, request.toJSON);
   const row = serializeRowHeader('J', id) + json + '\n';
-  return convertStringToBuffer(row);
+  return stringToChunk(row);
 }
 
 export function processModuleChunk(
@@ -106,7 +106,7 @@ export function processModuleChunk(
 ): Chunk {
   const json = stringify(moduleMetaData);
   const row = serializeRowHeader('M', id) + json + '\n';
-  return convertStringToBuffer(row);
+  return stringToChunk(row);
 }
 
 export function processSymbolChunk(
@@ -116,7 +116,7 @@ export function processSymbolChunk(
 ): Chunk {
   const json = stringify(name);
   const row = serializeRowHeader('S', id) + json + '\n';
-  return convertStringToBuffer(row);
+  return stringToChunk(row);
 }
 
 export {
diff --git a/packages/react-server/src/ReactServerStreamConfigBrowser.js b/packages/react-server/src/ReactServerStreamConfigBrowser.js
index efcef78509cb..3714be430276 100644
--- a/packages/react-server/src/ReactServerStreamConfigBrowser.js
+++ b/packages/react-server/src/ReactServerStreamConfigBrowser.js
@@ -9,6 +9,9 @@
 
 export type Destination = ReadableStreamController;
 
+export type PrecomputedChunk = Uint8Array;
+export type Chunk = Uint8Array;
+
 export function scheduleWork(callback: () => void) {
   callback();
 }
@@ -22,9 +25,9 @@ export function beginWriting(destination: Destination) {}
 
 export function writeChunk(
   destination: Destination,
-  buffer: Uint8Array,
+  chunk: PrecomputedChunk | Chunk,
 ): boolean {
-  destination.enqueue(buffer);
+  destination.enqueue(chunk);
   return destination.desiredSize > 0;
 }
 
@@ -36,7 +39,11 @@ export function close(destination: Destination) {
 
 const textEncoder = new TextEncoder();
 
-export function convertStringToBuffer(content: string): Uint8Array {
+export function stringToChunk(content: string): Chunk {
+  return textEncoder.encode(content);
+}
+
+export function stringToPrecomputedChunk(content: string): PrecomputedChunk {
   return textEncoder.encode(content);
 }
 
diff --git a/packages/react-server/src/ReactServerStreamConfigNode.js b/packages/react-server/src/ReactServerStreamConfigNode.js
index 00e3364fc93a..4329554b7f05 100644
--- a/packages/react-server/src/ReactServerStreamConfigNode.js
+++ b/packages/react-server/src/ReactServerStreamConfigNode.js
@@ -18,6 +18,9 @@ type MightBeFlushable = {
 
 export type Destination = Writable & MightBeFlushable;
 
+export type PrecomputedChunk = Uint8Array;
+export type Chunk = string;
+
 export function scheduleWork(callback: () => void) {
   setImmediate(callback);
 }
@@ -44,9 +47,9 @@ export function beginWriting(destination: Destination) {
 
 export function writeChunk(
   destination: Destination,
-  buffer: Uint8Array,
+  chunk: Chunk | PrecomputedChunk,
 ): boolean {
-  const nodeBuffer = ((buffer: any): Buffer); // close enough
+  const nodeBuffer = ((chunk: any): Buffer | string); // close enough
   return destination.write(nodeBuffer);
 }
 
@@ -61,7 +64,11 @@ export function close(destination: Destination) {
   destination.end();
 }
 
-export function convertStringToBuffer(content: string): Uint8Array {
+export function stringToChunk(content: string): Chunk {
+  return content;
+}
+
+export function stringToPrecomputedChunk(content: string): PrecomputedChunk {
   return Buffer.from(content, 'utf8');
 }
 
diff --git a/packages/react-server/src/forks/ReactServerStreamConfig.custom.js b/packages/react-server/src/forks/ReactServerStreamConfig.custom.js
index 276659596737..e832f19430a2 100644
--- a/packages/react-server/src/forks/ReactServerStreamConfig.custom.js
+++ b/packages/react-server/src/forks/ReactServerStreamConfig.custom.js
@@ -26,6 +26,9 @@
 declare var $$$hostConfig: any;
 export opaque type Destination = mixed; // eslint-disable-line no-undef
 
+export opaque type PrecomputedChunk = mixed; // eslint-disable-line no-undef
+export opaque type Chunk = mixed; // eslint-disable-line no-undef
+
 export const scheduleWork = $$$hostConfig.scheduleWork;
 export const beginWriting = $$$hostConfig.beginWriting;
 export const writeChunk = $$$hostConfig.writeChunk;
@@ -33,4 +36,5 @@ export const completeWriting = $$$hostConfig.completeWriting;
 export const flushBuffered = $$$hostConfig.flushBuffered;
 export const close = $$$hostConfig.close;
 export const closeWithError = $$$hostConfig.closeWithError;
-export const convertStringToBuffer = $$$hostConfig.convertStringToBuffer;
+export const stringToChunk = $$$hostConfig.stringToChunk;
+export const stringToPrecomputedChunk = $$$hostConfig.stringToPrecomputedChunk;