diff --git a/packages/insomnia-data/src/models/response.ts b/packages/insomnia-data/src/models/response.ts
index 87c7614de3..cc356dce16 100644
--- a/packages/insomnia-data/src/models/response.ts
+++ b/packages/insomnia-data/src/models/response.ts
@@ -34,7 +34,7 @@ export interface BaseResponse {
   headers: ResponseHeader[];
   bodyPath: string;
   // if body is less than 5MB, it's stored in memory
-  bodyBuffer?: Buffer;
+  bodyBuffer?: Uint8Array;
   // Actual bodies are stored on the filesystem
   timelinePath: string;
   // Actual timelines are stored on the filesystem
diff --git a/packages/insomnia/src/main/ipc/main.ts b/packages/insomnia/src/main/ipc/main.ts
index e533f32adf..2daa99915c 100644
--- a/packages/insomnia/src/main/ipc/main.ts
+++ b/packages/insomnia/src/main/ipc/main.ts
@@ -204,8 +204,8 @@ export interface RendererToMainBridgeAPI {
   installPlugin: typeof installPlugin;
   initializeWorkspaceBackendProject: typeof initializeWorkspaceBackendProject;
   parseImport: typeof convert;
-  multipartBufferToArray: (options: { bodyBuffer: Buffer; contentType: string }) => Promise<Part[]>;
-  writeFile: (options: { path: string; content: string | Buffer }) => Promise<string>;
+  multipartBufferToArray: (options: { bodyBuffer: Uint8Array | null; contentType: string }) => Promise<Part[]>;
+  writeFile: (options: { path: string; content: string | Uint8Array }) => Promise<string>;
   deleteCompiledRuleset: (options: { projectId: string }) => Promise<void>;
   refreshCompiledRuleset: (options: { projectId: string; rulesetContent: string }) => Promise<{ compiledPath: string }>;
   writeResponseBodyToFile: (options: {
@@ -377,12 +377,7 @@ export function registerMainHandlers() {
       throw new TypeError(`Unknown service method: ${serviceName}.${methodName}`);
     }
     const result = await (fn as (...args: unknown[]) => unknown).call(service, ...args);
-    // Tag Buffer results before contextBridge serializes them as plain Uint8Array,
-    // so the preload can distinguish them from intentional Uint8Array returns.
-    if (Buffer.isBuffer(result)) {
-      return { __type: 'Buffer', data: Array.from(result as Buffer) };
-    }
-    return result;
+    return Buffer.isBuffer(result) ? new Uint8Array(result) : result;
   });
   ipcMainHandle('multipartBufferToArray', async (_, options) => {
     return multipartBufferToArray(options);
@@ -426,7 +421,7 @@ export function registerMainHandlers() {
       return initializeWorkspaceBackendProject(options);
     },
   );
-  ipcMainHandle('writeFile', async (_, options: { path: string; content: string | Buffer }) => {
+  ipcMainHandle('writeFile', async (_, options: { path: string; content: string | Uint8Array }) => {
     try {
       const dir = path.dirname(options.path);
       await fs.promises.mkdir(dir, { recursive: true });
diff --git a/packages/insomnia/src/main/multipart-buffer-to-array.ts b/packages/insomnia/src/main/multipart-buffer-to-array.ts
index e1bcdef99a..5e4c3cee05 100644
--- a/packages/insomnia/src/main/multipart-buffer-to-array.ts
+++ b/packages/insomnia/src/main/multipart-buffer-to-array.ts
@@ -7,7 +7,7 @@ export interface Part {
   title: string;
   name: string;
   bytes: number;
-  value: Buffer;
+  value: Uint8Array;
   filename: string | null;
   headers: { name: string; value: string }[];
 }
@@ -15,7 +15,7 @@ export function multipartBufferToArray({
   bodyBuffer,
   contentType,
 }: {
-  bodyBuffer: Buffer | null;
+  bodyBuffer: Uint8Array | null;
   contentType: string;
 }): Promise<Part[]> {
   return new Promise((resolve, reject) => {
diff --git a/packages/insomnia/src/network/basic-auth/get-header.ts b/packages/insomnia/src/network/basic-auth/get-header.ts
index 7937af85ff..ea6000d1a1 100644
--- a/packages/insomnia/src/network/basic-auth/get-header.ts
+++ b/packages/insomnia/src/network/basic-auth/get-header.ts
@@ -1,10 +1,11 @@
 import type { RequestHeader } from 'insomnia-data';
 
+import { bytesToBase64, latin1BytesFromString, utf8ToBase64 } from '~/utils/utf8-bytes';
+
 export function getBasicAuthHeader(username?: string | null, password?: string | null, encoding = 'utf8') {
   const name = 'Authorization';
   const header = `${username || ''}:${password || ''}`;
-  // @ts-expect-error -- TSCONVERSION appears to be a genuine error
-  const authString = Buffer.from(header, encoding).toString('base64');
+  const authString = encoding === 'latin1' ? bytesToBase64(latin1BytesFromString(header)) : utf8ToBase64(header);
   const value = `Basic ${authString}`;
   const requestHeader: RequestHeader = {
     name,
diff --git a/packages/insomnia/src/routes/organization.$organizationId.project.$projectId.workspace.$workspaceId.debug.request.$requestId.tsx b/packages/insomnia/src/routes/organization.$organizationId.project.$projectId.workspace.$workspaceId.debug.request.$requestId.tsx
index 2e58e8e086..8582ef05af 100644
--- a/packages/insomnia/src/routes/organization.$organizationId.project.$projectId.workspace.$workspaceId.debug.request.$requestId.tsx
+++ b/packages/insomnia/src/routes/organization.$organizationId.project.$projectId.workspace.$workspaceId.debug.request.$requestId.tsx
@@ -173,7 +173,7 @@ export async function clientLoader({ params }: Route.ClientLoaderArgs) {
     // Oversized repsonses are handled in the response-viewer.tsx for now
     if (!isOversizedResponse) {
       const buffer = await services.helpers.getResponseBodyBuffer(activeResponse);
-      activeResponse.bodyBuffer = typeof buffer === 'string' ? Buffer.from(buffer) : buffer;
+      activeResponse.bodyBuffer = typeof buffer === 'string' ? undefined : buffer;
     }
   }
 
diff --git a/packages/insomnia/src/routes/organization.$organizationId.project.$projectId.workspace.$workspaceId.mock-server.mock-route.$mockRouteId.tsx b/packages/insomnia/src/routes/organization.$organizationId.project.$projectId.workspace.$workspaceId.mock-server.mock-route.$mockRouteId.tsx
index e05d4094a0..ad0b009775 100644
--- a/packages/insomnia/src/routes/organization.$organizationId.project.$projectId.workspace.$workspaceId.mock-server.mock-route.$mockRouteId.tsx
+++ b/packages/insomnia/src/routes/organization.$organizationId.project.$projectId.workspace.$workspaceId.mock-server.mock-route.$mockRouteId.tsx
@@ -33,6 +33,7 @@ import { EmptyStatePane } from '~/ui/components/panes/empty-state-pane';
 import { Pane, PaneBody, PaneHeader } from '~/ui/components/panes/pane';
 import { SvgIcon } from '~/ui/components/svg-icon';
 import { invariant } from '~/utils/invariant';
+import { utf8ByteLength } from '~/utils/utf8-bytes';
 
 import type { Route } from './+types/organization.$organizationId.project.$projectId.workspace.$workspaceId.mock-server.mock-route.$mockRouteId';
 
@@ -65,7 +66,7 @@ export async function clientLoader({ params }: Route.ClientLoaderArgs) {
     // Oversized responses are handled in the response-viewer.tsx for now
     if (!isOversizedResponse) {
       const buffer = await services.helpers.getResponseBodyBuffer(activeResponse);
-      activeResponse.bodyBuffer = typeof buffer === 'string' ? Buffer.from(buffer) : buffer;
+      activeResponse.bodyBuffer = typeof buffer === 'string' ? undefined : buffer;
     }
   }
   return {
@@ -106,7 +107,7 @@ export const mockRouteToHar = async ({
     headers: validHeaders,
     cookies: await window.main.cookies.getResponseCookiesFromHeaders(validHeaders),
     content: {
-      size: Buffer.byteLength(body),
+      size: utf8ByteLength(body),
       mimeType,
       text: body,
       compression: 0,
diff --git a/packages/insomnia/src/routes/organization.$organizationId.project.$projectId.workspace.$workspaceId.spec.tsx b/packages/insomnia/src/routes/organization.$organizationId.project.$projectId.workspace.$workspaceId.spec.tsx
index 221768d857..d8d87e9d91 100644
--- a/packages/insomnia/src/routes/organization.$organizationId.project.$projectId.workspace.$workspaceId.spec.tsx
+++ b/packages/insomnia/src/routes/organization.$organizationId.project.$projectId.workspace.$workspaceId.spec.tsx
@@ -62,6 +62,7 @@ import { useLoaderDeferData } from '~/ui/hooks/use-loader-defer-data';
 import { useAIFeatureStatus } from '~/ui/hooks/use-organization-features';
 import { useGitVCSVersion } from '~/ui/hooks/use-vcs-version';
 import { DEFAULT_STORAGE_RULES } from '~/ui/organization-utils';
+import { utf8ByteLength } from '~/utils/utf8-bytes';
 
 import type { Route } from './+types/organization.$organizationId.project.$projectId.workspace.$workspaceId.spec';
 
@@ -435,8 +436,7 @@ const Component = ({ params }: Route.ComponentProps) => {
     }
 
     const RULESET_MAX_BYTES = 1 * 1024 * 1024; // 1 MB
-    const byteLength = new TextEncoder().encode(content).byteLength;
-    if (byteLength > RULESET_MAX_BYTES) {
+    if (utf8ByteLength(content) > RULESET_MAX_BYTES) {
       showError({
         title: 'Ruleset Too Large',
         message: 'The selected ruleset exceeds the maximum allowed size of 1 MB.',
diff --git a/packages/insomnia/src/templating/local-template-tags.ts b/packages/insomnia/src/templating/local-template-tags.ts
index 5e82b5b773..f49b7b57e1 100644
--- a/packages/insomnia/src/templating/local-template-tags.ts
+++ b/packages/insomnia/src/templating/local-template-tags.ts
@@ -2,6 +2,7 @@ import { format } from 'date-fns';
 import type { TemplateTag } from 'insomnia/src/plugins/types';
 import type { PluginTemplateTag } from 'insomnia/src/templating/types';
 import { invariant } from 'insomnia/src/utils/invariant';
+import { utf8StringFromBytes } from 'insomnia/src/utils/utf8-bytes';
 import JSONBig from 'json-bigint';
 import { JSONPath } from 'jsonpath-plus';
 
@@ -673,7 +674,7 @@ const localTemplatePlugins: { templateTag: PluginTemplateTag }[] = [
             return context.util.decode(bodyBuffer, charset);
           } catch (err) {
             console.warn('[response] Failed to decode body', err);
-            return bodyBuffer.toString();
+            return utf8StringFromBytes(bodyBuffer);
           }
         }
         if (field === 'header') {
@@ -698,7 +699,7 @@ const localTemplatePlugins: { templateTag: PluginTemplateTag }[] = [
             body = await context.util.decode(bodyBuffer, charset);
           } catch (err) {
             console.warn('[response] Failed to decode body', err);
-            body = bodyBuffer.toString();
+            body = utf8StringFromBytes(bodyBuffer);
           }
 
           if (sanitizedFilter.indexOf('$') === 0) {
diff --git a/packages/insomnia/src/templating/utils.ts b/packages/insomnia/src/templating/utils.ts
index 4b6cb562ba..49a95a1052 100644
--- a/packages/insomnia/src/templating/utils.ts
+++ b/packages/insomnia/src/templating/utils.ts
@@ -2,6 +2,7 @@ import type { EditorFromTextArea, MarkerRange } from 'codemirror';
 import { models, services } from 'insomnia-data';
 
 import { decryptSecretValue } from '~/utils/crypt-adapter';
+import { base64ToUtf8, utf8ToBase64 } from '~/utils/utf8-bytes';
 
 import type { NunjucksParsedTag, NunjucksParsedTagArg, RenderPurpose } from '../templating/types';
 import { decryptVaultKeyFromSession } from '../utils/vault';
@@ -122,7 +123,7 @@ export function encodeEncoding<T>(value: T, encoding?: 'base64') {
   }
 
   if (encoding === 'base64') {
-    const encodedValue = Buffer.from(value, 'utf8').toString('base64');
+    const encodedValue = utf8ToBase64(value);
     return `b64::${encodedValue}::46b`;
   }
 
@@ -137,11 +138,7 @@ export function decodeEncoding<T>(value: T) {
   const results = value.match(/^b64::(.+)::46b$/);
 
   if (results) {
-    if (typeof Buffer !== 'undefined') {
-      return Buffer.from(results[1], 'base64').toString('utf8');
-    }
-    // Fallback for browser environments
-    return atob(results[1]);
+    return base64ToUtf8(results[1]);
   }
 
   return value;
diff --git a/packages/insomnia/src/ui/components/base/prompt-button.tsx b/packages/insomnia/src/ui/components/base/prompt-button.tsx
index 583630c900..1643844bfc 100644
--- a/packages/insomnia/src/ui/components/base/prompt-button.tsx
+++ b/packages/insomnia/src/ui/components/base/prompt-button.tsx
@@ -41,9 +41,8 @@ export const PromptButton = <T,>({
   // Create flag to store the state value.
   const [state, setState] = useState<PromptStateEnum>('default');
 
-  // Timeout instancies
-  const doneTimeout = useRef<NodeJS.Timeout | null>(null);
-  const triggerTimeout = useRef<NodeJS.Timeout | null>(null);
+  const doneTimeout = useRef<number | null>(null);
+  const triggerTimeout = useRef<number | null>(null);
 
   useEffect(() => {
     return () => {
@@ -59,9 +58,7 @@ export const PromptButton = <T,>({
       event.stopPropagation();
       // Toggle the confirmation notice
       setState('ask');
-      // Set a timeout to hide the confirmation
-      // using global.setTimeout to force use of the Node timeout rather than DOM timeout
-      triggerTimeout.current = global.setTimeout(() => {
+      triggerTimeout.current = window.setTimeout(() => {
         setState('default');
       }, 2000);
     }
@@ -73,14 +70,10 @@ export const PromptButton = <T,>({
       // Fire the click handler
       const retVal: any = onClick?.(event);
       if (!referToOnClickReturnValue) {
-        // Set the state to done (but delay a bit to not alarm user)
-        // using global.setTimeout to force use of the Node timeout rather than DOM timeout
-        doneTimeout.current = global.setTimeout(() => {
+        doneTimeout.current = window.setTimeout(() => {
           setState('done');
         }, 100);
-        // Set a timeout to hide the confirmation
-        // using global.setTimeout to force use of the Node timeout rather than DOM timeout
-        triggerTimeout.current = global.setTimeout(() => {
+        triggerTimeout.current = window.setTimeout(() => {
           setState('default');
         }, 2000);
       } else {
@@ -91,7 +84,7 @@ export const PromptButton = <T,>({
               setState('done');
             })
             .finally(() => {
-              triggerTimeout.current = global.setTimeout(() => {
+              triggerTimeout.current = window.setTimeout(() => {
                 setState('default');
               }, 1000);
             });
diff --git a/packages/insomnia/src/ui/components/dropdowns/preview-mode-dropdown.tsx b/packages/insomnia/src/ui/components/dropdowns/preview-mode-dropdown.tsx
index 5d547c84b5..191397f21a 100644
--- a/packages/insomnia/src/ui/components/dropdowns/preview-mode-dropdown.tsx
+++ b/packages/insomnia/src/ui/components/dropdowns/preview-mode-dropdown.tsx
@@ -3,6 +3,8 @@ import { getPreviewModeName, PREVIEW_MODE_SOURCE, PREVIEW_MODES } from 'insomnia
 import React, { type FC, useCallback } from 'react';
 import { Button } from 'react-aria-components';
 
+import { bodyBufferToUtf8 } from '~/utils/utf8-bytes';
+
 import {
   type RequestLoaderData,
   useRequestLoaderData,
@@ -81,7 +83,7 @@ export const PreviewModeDropdown: FC<Props> = ({ download, copyToClipboard }) =>
     if (filePath && activeResponse.bodyBuffer) {
       await window.main.writeFile({
         path: filePath,
-        content: headers + '\n' + activeResponse.bodyBuffer.toString('utf8') || '',
+        content: headers + '\n' + bodyBufferToUtf8(activeResponse.bodyBuffer) || '',
       });
     }
   }, [activeRequest, activeResponse]);
diff --git a/packages/insomnia/src/ui/components/editors/body/graph-ql-editor.tsx b/packages/insomnia/src/ui/components/editors/body/graph-ql-editor.tsx
index ec5ff7e26e..84e5fa3596 100644
--- a/packages/insomnia/src/ui/components/editors/body/graph-ql-editor.tsx
+++ b/packages/insomnia/src/ui/components/editors/body/graph-ql-editor.tsx
@@ -25,6 +25,7 @@ import { Panel, PanelGroup, PanelResizeHandle } from 'react-resizable-panels';
 import * as reactUse from 'react-use';
 
 import { CodeEditor, type CodeEditorHandle } from '~/ui/components/.client/codemirror/code-editor';
+import { bodyBufferToUtf8 } from '~/utils/utf8-bytes';
 
 import { CONTENT_TYPE_JSON } from '../../../../common/constants';
 import { database as db } from '../../../../common/database';
@@ -186,7 +187,7 @@ const fetchGraphQLSchemaForRequest = async ({
     }
     const bodyBuffer = await services.helpers.getResponseBodyBuffer(response);
     if (bodyBuffer) {
-      const { data, errors } = JSON.parse(bodyBuffer.toString());
+      const { data, errors } = JSON.parse(bodyBufferToUtf8(bodyBuffer));
       if (errors?.length) {
         return { schemaFetchError: errors[0] };
       }
diff --git a/packages/insomnia/src/ui/components/key-value-editor/key-value-editor.tsx b/packages/insomnia/src/ui/components/key-value-editor/key-value-editor.tsx
index dff5335232..9e1e656951 100644
--- a/packages/insomnia/src/ui/components/key-value-editor/key-value-editor.tsx
+++ b/packages/insomnia/src/ui/components/key-value-editor/key-value-editor.tsx
@@ -14,6 +14,7 @@ import {
 } from 'react-aria-components';
 
 import { OneLineEditor } from '~/ui/components/.client/codemirror/one-line-editor';
+import { utf8ByteLength } from '~/utils/utf8-bytes';
 
 import { describeByteSize, generateId } from '../../../common/misc';
 import { FileInputButton } from '../base/file-input-button';
@@ -131,7 +132,7 @@ export const KeyValueEditor: FC<Props> = ({
 
       const isFile = 'type' in pair && pair.type === 'file';
       const isMultiline = 'type' in pair && pair.type === 'text' && pair.multiline;
-      const bytes = isMultiline ? Buffer.from(pair.value, 'utf8').length : 0;
+      const bytes = isMultiline ? utf8ByteLength(pair.value) : 0;
 
       let valueEditor = (
         <div className="relative flex h-full w-full flex-1 px-2">
@@ -291,7 +292,7 @@ export const KeyValueEditor: FC<Props> = ({
           {pair => {
             const isFile = pair.type === 'file';
             const isMultiline = pair.type === 'text' && pair.multiline;
-            const bytes = isMultiline ? Buffer.from(pair.value, 'utf8').length : 0;
+            const bytes = isMultiline ? utf8ByteLength(pair.value) : 0;
             const lowerName = pair.name.toLowerCase();
             const isPairDisabled = !!readOnlyDisabledByName?.[lowerName];
 
@@ -394,7 +395,7 @@ export const KeyValueEditor: FC<Props> = ({
           {pair => {
             const isFile = pair.type === 'file';
             const isMultiline = pair.type === 'text' && pair.multiline;
-            const bytes = isMultiline ? Buffer.from(pair.value, 'utf8').length : 0;
+            const bytes = isMultiline ? utf8ByteLength(pair.value) : 0;
             const isOnlyTextAllowed = !allowFile && !allowMultiline;
 
             let valueEditor = (
diff --git a/packages/insomnia/src/ui/components/key-value-editor/row.tsx b/packages/insomnia/src/ui/components/key-value-editor/row.tsx
index 7d49ec11c0..2e503c3331 100644
--- a/packages/insomnia/src/ui/components/key-value-editor/row.tsx
+++ b/packages/insomnia/src/ui/components/key-value-editor/row.tsx
@@ -3,6 +3,7 @@ import React, { type FC } from 'react';
 import { Button } from 'react-aria-components';
 
 import { OneLineEditor } from '~/ui/components/.client/codemirror/one-line-editor';
+import { utf8ByteLength } from '~/utils/utf8-bytes';
 
 import { describeByteSize } from '../../../common/misc';
 import { Dropdown, DropdownItem, ItemContent } from '../base/dropdown';
@@ -78,7 +79,7 @@ export const Row: FC<Props> = ({
 
   const isFile = pair.type === 'file';
   const isMultiline = pair.type === 'text' && pair.multiline;
-  const bytes = isMultiline ? Buffer.from(pair.value, 'utf8').length : 0;
+  const bytes = isMultiline ? utf8ByteLength(pair.value) : 0;
 
   return (
     <li onKeyDown={onKeydown} onClick={onClick} className={classes}>
diff --git a/packages/insomnia/src/ui/components/mocks/mock-response-pane.tsx b/packages/insomnia/src/ui/components/mocks/mock-response-pane.tsx
index 9c45211b07..29dc277218 100644
--- a/packages/insomnia/src/ui/components/mocks/mock-response-pane.tsx
+++ b/packages/insomnia/src/ui/components/mocks/mock-response-pane.tsx
@@ -10,6 +10,7 @@ import { useRootLoaderData } from '~/root';
 import { useRequestNewMockSendActionFetcher } from '~/routes/organization.$organizationId.project.$projectId.workspace.$workspaceId.debug.request.new-mock-send';
 import { useMockRouteLoaderData } from '~/routes/organization.$organizationId.project.$projectId.workspace.$workspaceId.mock-server.mock-route.$mockRouteId';
 import { CodeEditor } from '~/ui/components/.client/codemirror/code-editor';
+import { bodyBufferToUtf8 } from '~/utils/utf8-bytes';
 
 import { getMockServiceURL } from '../../../common/constants';
 import { cancelRequestById } from '../../../network/cancellation';
@@ -293,7 +294,7 @@ const PreviewModeDropdown = ({
             label="Copy raw response"
             onClick={async () => {
               const bodyBuffer = await services.helpers.getResponseBodyBuffer(activeResponse);
-              bodyBuffer && window.clipboard.writeText(bodyBuffer.toString('utf8'));
+              bodyBuffer && window.clipboard.writeText(bodyBufferToUtf8(bodyBuffer));
             }}
           />
         </DropdownItem>
@@ -313,7 +314,7 @@ const PreviewModeDropdown = ({
               }
               await window.main.writeFile({
                 path: filePath,
-                content: activeResponse.bodyBuffer?.toString('utf8') || '',
+                content: bodyBufferToUtf8(activeResponse.bodyBuffer) || '',
               });
             }}
           />
@@ -336,7 +337,7 @@ const PreviewModeDropdown = ({
                 }
                 await window.main.writeFile({
                   path: filePath,
-                  content: jsonPrettify(activeResponse.bodyBuffer?.toString('utf8')) || '',
+                  content: jsonPrettify(bodyBufferToUtf8(bodyBuffer)) || '',
                 });
               }}
             />
diff --git a/packages/insomnia/src/ui/components/panes/__tests__/response-pane-utils.test.ts b/packages/insomnia/src/ui/components/panes/__tests__/response-pane-utils.test.ts
index a1891df1cf..7669969d34 100644
--- a/packages/insomnia/src/ui/components/panes/__tests__/response-pane-utils.test.ts
+++ b/packages/insomnia/src/ui/components/panes/__tests__/response-pane-utils.test.ts
@@ -34,7 +34,7 @@ describe('downloadResponseBody', () => {
 
       await downloadResponseBody(
         null,
-        { contentType: 'application/json', bodyBuffer: Buffer.from('{}') },
+        { contentType: 'application/json', bodyBuffer: new TextEncoder().encode('{}') },
         false,
       );
 
@@ -50,7 +50,7 @@ describe('downloadResponseBody', () => {
 
       await downloadResponseBody(
         { name: 'My Request' },
-        { contentType: 'application/json', bodyBuffer: Buffer.from('{}') },
+        { contentType: 'application/json', bodyBuffer: new TextEncoder().encode('{}') },
         false,
       );
 
@@ -60,20 +60,20 @@ describe('downloadResponseBody', () => {
   });
 
   describe('prettify branch (prettify=true, JSON content-type)', () => {
-    it('writes a prettified JSON string, not a Buffer', async () => {
+    it('writes a prettified JSON string, not raw bytes', async () => {
       mockShowSaveDialog.mockResolvedValue({ canceled: false, filePath: '/tmp/out.json' });
       const rawJson = '{"b":2,"a":1}';
 
       await downloadResponseBody(
         { name: 'My Request' },
-        { contentType: 'application/json', bodyBuffer: Buffer.from(rawJson) },
+        { contentType: 'application/json', bodyBuffer: new TextEncoder().encode(rawJson) },
         true,
       );
 
       expect(mockWriteFile).toHaveBeenCalledOnce();
       const { path, content } = mockWriteFile.mock.calls[0][0];
       expect(path).toBe('/tmp/out.json');
-      // content must be a formatted string, not a Buffer
+      // content must be a formatted string, not raw bytes
       expect(typeof content).toBe('string');
       expect(content).toContain('"b": 2');
       expect(content).toContain('"a": 1');
@@ -81,10 +81,10 @@ describe('downloadResponseBody', () => {
   });
 
   describe('raw-bytes branch (default)', () => {
-    it('writes the raw Buffer when prettify is false, preserving binary content', async () => {
+    it('writes raw bytes when prettify is false, preserving binary content', async () => {
       mockShowSaveDialog.mockResolvedValue({ canceled: false, filePath: '/tmp/out.png' });
       // PNG magic bytes — would be corrupted by a UTF-8 round-trip
-      const binaryData = Buffer.from([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a]);
+      const binaryData = new Uint8Array([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a]);
 
       await downloadResponseBody(
         { name: 'My Request' },
@@ -95,13 +95,13 @@ describe('downloadResponseBody', () => {
       expect(mockWriteFile).toHaveBeenCalledOnce();
       const { path, content } = mockWriteFile.mock.calls[0][0];
       expect(path).toBe('/tmp/out.png');
-      expect(Buffer.isBuffer(content)).toBe(true);
+      expect(content).toBeInstanceOf(Uint8Array);
       expect(content).toEqual(binaryData);
     });
 
-    it('writes the raw Buffer when prettify is true but the content-type is not JSON', async () => {
+    it('writes raw bytes when prettify is true but the content-type is not JSON', async () => {
       mockShowSaveDialog.mockResolvedValue({ canceled: false, filePath: '/tmp/out.txt' });
-      const textData = Buffer.from('Hello, World!');
+      const textData = new TextEncoder().encode('Hello, World!');
 
       await downloadResponseBody(
         { name: 'My Request' },
@@ -111,11 +111,11 @@ describe('downloadResponseBody', () => {
 
       expect(mockWriteFile).toHaveBeenCalledOnce();
       const { content } = mockWriteFile.mock.calls[0][0];
-      expect(Buffer.isBuffer(content)).toBe(true);
+      expect(content).toBeInstanceOf(Uint8Array);
       expect(content).toEqual(textData);
     });
 
-    it('writes an empty Buffer when bodyBuffer is null', async () => {
+    it('writes empty bytes when bodyBuffer is null', async () => {
       mockShowSaveDialog.mockResolvedValue({ canceled: false, filePath: '/tmp/out.bin' });
 
       await downloadResponseBody(
@@ -126,7 +126,7 @@ describe('downloadResponseBody', () => {
 
       expect(mockWriteFile).toHaveBeenCalledOnce();
       const { content } = mockWriteFile.mock.calls[0][0];
-      expect(Buffer.isBuffer(content)).toBe(true);
+      expect(content).toBeInstanceOf(Uint8Array);
       expect(content.length).toBe(0);
     });
   });
diff --git a/packages/insomnia/src/ui/components/panes/response-pane-utils.ts b/packages/insomnia/src/ui/components/panes/response-pane-utils.ts
index d041cc3f5e..c10e9d14c2 100644
--- a/packages/insomnia/src/ui/components/panes/response-pane-utils.ts
+++ b/packages/insomnia/src/ui/components/panes/response-pane-utils.ts
@@ -1,10 +1,11 @@
 import { extension as mimeExtension } from 'mime-types';
 
 import { jsonPrettify } from '~/utils/prettify/json';
+import { bodyBufferToUtf8 } from '~/utils/utf8-bytes';
 
 export async function downloadResponseBody(
   activeRequest: { name: string } | null | undefined,
-  activeResponse: { contentType: string; bodyBuffer?: Buffer | null } | null | undefined,
+  activeResponse: { contentType: string; bodyBuffer?: Uint8Array | null } | null | undefined,
   prettify: boolean,
 ) {
   if (!activeResponse || !activeRequest) {
@@ -26,9 +27,9 @@ export async function downloadResponseBody(
   if (prettify && contentType.includes('json')) {
     await window.main.writeFile({
       path: outputPath,
-      content: jsonPrettify(activeResponse.bodyBuffer?.toString('utf8')) || '',
+      content: jsonPrettify(bodyBufferToUtf8(activeResponse.bodyBuffer)) || '',
     });
     return;
   }
-  await window.main.writeFile({ path: outputPath, content: activeResponse.bodyBuffer ?? Buffer.alloc(0) });
+  await window.main.writeFile({ path: outputPath, content: activeResponse.bodyBuffer ?? new Uint8Array(0) });
 }
diff --git a/packages/insomnia/src/ui/components/panes/response-pane.tsx b/packages/insomnia/src/ui/components/panes/response-pane.tsx
index 4d2fc7a94c..8781415462 100644
--- a/packages/insomnia/src/ui/components/panes/response-pane.tsx
+++ b/packages/insomnia/src/ui/components/panes/response-pane.tsx
@@ -6,6 +6,7 @@ import { Tab, TabList, TabPanel, Tabs, Toolbar } from 'react-aria-components';
 
 import { useRootLoaderData } from '~/root';
 import { AnalyticsEvent } from '~/ui/analytics';
+import { bodyBufferToUtf8 } from '~/utils/utf8-bytes';
 
 import { getSetCookieHeaders } from '../../../common/misc';
 import { cancelRequestById } from '../../../network/cancellation';
@@ -219,7 +220,7 @@ export const ResponsePane: FC<Props> = ({ activeRequestId }) => {
               copyToClipboard={async () => {
                 const bodyBuffer = activeResponse ? await services.helpers.getResponseBodyBuffer(activeResponse) : null;
                 if (bodyBuffer) {
-                  window.clipboard.writeText(bodyBuffer.toString('utf8'));
+                  window.clipboard.writeText(bodyBufferToUtf8(bodyBuffer));
                 }
               }}
             />
diff --git a/packages/insomnia/src/ui/components/viewers/response-csv-viewer.tsx b/packages/insomnia/src/ui/components/viewers/response-csv-viewer.tsx
index 8335caf198..d483c734c5 100644
--- a/packages/insomnia/src/ui/components/viewers/response-csv-viewer.tsx
+++ b/packages/insomnia/src/ui/components/viewers/response-csv-viewer.tsx
@@ -1,8 +1,10 @@
 import Papa from 'papaparse';
 import React, { type FC, useEffect, useRef, useState } from 'react';
 
+import { utf8StringFromBytes } from '~/utils/utf8-bytes';
+
 interface Props {
-  body: Buffer;
+  body: Uint8Array;
 }
 
 export const ResponseCSVViewer: FC<Props> = ({ body }) => {
@@ -10,7 +12,7 @@ export const ResponseCSVViewer: FC<Props> = ({ body }) => {
   const tableRef = useRef<HTMLTableElement>(null);
 
   useEffect(() => {
-    Papa.parse<string[]>(body.toString('utf8'), {
+    Papa.parse<string[]>(utf8StringFromBytes(body), {
       skipEmptyLines: true,
       complete: result => {
         setCSV(result);
diff --git a/packages/insomnia/src/ui/components/viewers/response-multipart-viewer.tsx b/packages/insomnia/src/ui/components/viewers/response-multipart-viewer.tsx
index abf24c6c55..9ab68dd35e 100644
--- a/packages/insomnia/src/ui/components/viewers/response-multipart-viewer.tsx
+++ b/packages/insomnia/src/ui/components/viewers/response-multipart-viewer.tsx
@@ -6,6 +6,7 @@ import React, { type FC, useCallback, useEffect, useState } from 'react';
 import { Button } from 'react-aria-components';
 
 import type { Part } from '~/main/multipart-buffer-to-array';
+import { utf8StringFromBytes } from '~/utils/utf8-bytes';
 
 import { Dropdown, DropdownItem, ItemContent } from '../base/dropdown';
 import { showModal } from '../modals/index';
@@ -16,7 +17,7 @@ import { ResponseViewer } from './response-viewer';
 interface Props {
   download: (...args: any[]) => any;
   responseId: string;
-  bodyBuffer: Buffer | null;
+  bodyBuffer: Uint8Array | null;
   contentType: string;
   disableHtmlPreviewJs: boolean;
   disablePreviewLinks: boolean;
@@ -105,7 +106,7 @@ export const ResponseMultipartViewer: FC<Props> = ({
     try {
       await window.main.writeFile({
         path: filePath,
-        content: selectedPart.value.toString('utf8'),
+        content: utf8StringFromBytes(selectedPart.value),
       });
     } catch (err) {
       console.warn('Failed to save multipart to file', err);
@@ -198,7 +199,7 @@ export const ResponseMultipartViewer: FC<Props> = ({
           error={null}
           filter={filter}
           filterHistory={filterHistory}
-          bodyBuffer={Buffer.from(selectedPart?.value || '')}
+          bodyBuffer={selectedPart?.value ?? new Uint8Array(0)}
           key={`${responseId}::${selectedPart?.id}`}
           previewMode={PREVIEW_MODE_FRIENDLY}
           responseId={`${responseId}[${selectedPart?.id}]`}
diff --git a/packages/insomnia/src/ui/components/viewers/response-pdf-viewer.tsx b/packages/insomnia/src/ui/components/viewers/response-pdf-viewer.tsx
index 8e8321c9d0..f690e236f1 100644
--- a/packages/insomnia/src/ui/components/viewers/response-pdf-viewer.tsx
+++ b/packages/insomnia/src/ui/components/viewers/response-pdf-viewer.tsx
@@ -1,7 +1,7 @@
 import { useEffect, useState } from 'react';
 
 interface Props {
-  body: Buffer;
+  body: Uint8Array;
 }
 
 export const ResponsePDFViewer = ({ body }: Props) => {
diff --git a/packages/insomnia/src/ui/components/viewers/response-viewer.tsx b/packages/insomnia/src/ui/components/viewers/response-viewer.tsx
index d57b4324d5..b91549ca62 100644
--- a/packages/insomnia/src/ui/components/viewers/response-viewer.tsx
+++ b/packages/insomnia/src/ui/components/viewers/response-viewer.tsx
@@ -3,6 +3,7 @@ import { Fragment, useCallback, useRef, useState } from 'react';
 
 import { AnalyticsEvent } from '~/ui/analytics';
 import { CodeEditor, type CodeEditorHandle } from '~/ui/components/.client/codemirror/code-editor';
+import { bytesToBase64, utf8StringFromBytes } from '~/utils/utf8-bytes';
 
 import { HUGE_RESPONSE_MB, LARGE_RESPONSE_MB } from '../../../common/constants';
 import { unescapeForwardSlash } from '../../../common/misc';
@@ -59,8 +60,8 @@ export interface ResponseViewerProps {
   editorFontSize: number;
   filter: string;
   filterHistory: string[];
-  bodyBuffer?: Buffer;
-  getBody?: (...args: any[]) => Promise<Buffer | string>;
+  bodyBuffer?: Uint8Array;
+  getBody?: (...args: any[]) => Promise<Uint8Array | string>;
   previewMode: string;
   responseId: string;
   url: string;
@@ -90,7 +91,7 @@ export const ResponseViewer = ({
   const [blockingBecauseTooLarge, setBlockingBecauseTooLarge] = useState(!alwaysShowLargeResponses && largeResponse);
   const [parseError, setParseError] = useState('');
 
-  const [overSizedBody, setOversizedBody] = useState<Buffer | null>(bodyBuffer || null);
+  const [overSizedBody, setOversizedBody] = useState<Uint8Array | null>(bodyBuffer || null);
 
   const editorRef = useRef<CodeEditorHandle>(null);
 
@@ -99,9 +100,12 @@ export const ResponseViewer = ({
 
     try {
       const buffer = await getBody?.();
-      const bufferOrError = typeof buffer === 'string' ? Buffer.from(buffer) : buffer;
+      if (typeof buffer === 'string') {
+        setParseError(`Failed reading response from filesystem: ${buffer}`);
+        return setOversizedBody(null);
+      }
 
-      return setOversizedBody(bufferOrError || null);
+      return setOversizedBody(buffer || null);
     } catch (err) {
       setParseError(`Failed reading response from filesystem: ${err.stack}`);
     }
@@ -137,7 +141,7 @@ export const ResponseViewer = ({
     // Apparently users often send JSON with weird content-types like text/plain.
     try {
       if (overSizedBody && overSizedBody.length > 0) {
-        JSON.parse(overSizedBody.toString('utf8'));
+        JSON.parse(utf8StringFromBytes(overSizedBody));
         return 'application/json';
       }
     } catch {}
@@ -145,9 +149,7 @@ export const ResponseViewer = ({
     // It is fairly common for webservers to send errors in HTML by default.
     // NOTE: This will probably never throw but I'm not 100% so wrap anyway
     try {
-      const isProbablyHTML = overSizedBody
-        .slice(0, 100)
-        .toString()
+      const isProbablyHTML = utf8StringFromBytes(overSizedBody.slice(0, 100))
         .trim()
         .match(/^<!doctype html.*>/i);
 
@@ -172,7 +174,7 @@ export const ResponseViewer = ({
       return new TextDecoder(label).decode(overSizedBody);
     } catch (err) {
       console.warn('[response] Failed to decode body', err);
-      return overSizedBody.toString();
+      return utf8StringFromBytes(overSizedBody);
     }
   }, [overSizedBody, _getContentType]);
 
@@ -274,7 +276,7 @@ export const ResponseViewer = ({
 
   if (previewMode === PREVIEW_MODE_FRIENDLY && contentType.indexOf('image/') === 0) {
     const justContentType = contentType.split(';')[0];
-    const base64Body = overSizedBody.toString('base64');
+    const base64Body = bytesToBase64(overSizedBody);
     return (
       <div className="scrollable-container tall wide">
         <div className="scrollable">
@@ -339,7 +341,7 @@ export const ResponseViewer = ({
 
   if (previewMode === PREVIEW_MODE_FRIENDLY && contentType.indexOf('audio/') === 0) {
     const justContentType = contentType.split(';')[0];
-    const base64Body = overSizedBody.toString('base64');
+    const base64Body = bytesToBase64(overSizedBody);
     return (
       <div className="vertically-center" key={responseId}>
         <audio controls>
diff --git a/packages/insomnia/src/ui/components/websockets/event-view.tsx b/packages/insomnia/src/ui/components/websockets/event-view.tsx
index 3d0c2e13c1..95b1da71c0 100644
--- a/packages/insomnia/src/ui/components/websockets/event-view.tsx
+++ b/packages/insomnia/src/ui/components/websockets/event-view.tsx
@@ -3,6 +3,7 @@ import React, { type FC, useCallback, useRef } from 'react';
 import { useParams } from 'react-router';
 
 import { CodeEditor, type CodeEditorHandle } from '~/ui/components/.client/codemirror/code-editor';
+import { utf8StringFromBytes } from '~/utils/utf8-bytes';
 
 import type { CurlEvent, CurlMessageEvent } from '../../../main/network/curl';
 import type { SocketIOEvent } from '../../../main/network/socket-io';
@@ -23,7 +24,7 @@ export const MessageEventView: FC<Props<CurlMessageEvent | WebSocketMessageEvent
   // Best effort to parse the binary data as a string
   try {
     if ('data' in event && typeof event.data === 'object' && 'data' in event.data && Array.isArray(event.data.data)) {
-      raw = Buffer.from(event.data.data).toString();
+      raw = utf8StringFromBytes(new Uint8Array(event.data.data));
     }
   } catch (err) {
     console.error('Failed to parse event data to string, defaulting to JSON.stringify', err);
diff --git a/packages/insomnia/src/ui/renderer-services-proxy.ts b/packages/insomnia/src/ui/renderer-services-proxy.ts
index c703648925..0b51bcd65f 100644
--- a/packages/insomnia/src/ui/renderer-services-proxy.ts
+++ b/packages/insomnia/src/ui/renderer-services-proxy.ts
@@ -8,17 +8,8 @@ export const servicesProxy = new Proxy({} as Services, {
       {},
       {
         get(_target, methodName: string) {
-          return async (...args: unknown[]) => {
-            const result = await invokeWithNormalizedError<any>('services.invoke', serviceName, methodName, ...args);
-            // contextBridge serializes Node.js Buffer as Uint8Array; the main process wraps
-            // Buffer results with { __type: 'Buffer', data } so we can safely reconstruct here
-            // without misidentifying genuine Uint8Array returns.
-            // TODO: remove once service methods stop returning Buffer (tracked for deprecation).
-            if (result && typeof result === 'object' && result.__type === 'Buffer' && Array.isArray(result.data)) {
-              return Buffer.from(result.data);
-            }
-            return result;
-          };
+          return (...args: unknown[]) =>
+            invokeWithNormalizedError<any>('services.invoke', serviceName, methodName, ...args);
         },
       },
     );
diff --git a/packages/insomnia/src/utils/utf8-bytes.test.ts b/packages/insomnia/src/utils/utf8-bytes.test.ts
new file mode 100644
index 0000000000..a8ed57acc5
--- /dev/null
+++ b/packages/insomnia/src/utils/utf8-bytes.test.ts
@@ -0,0 +1,37 @@
+import { describe, expect, it } from 'vitest';
+
+import { base64ToUtf8, bytesToBase64, latin1BytesFromString, utf8ByteLength, utf8ToBase64 } from './utf8-bytes';
+
+describe('utf8 byte helpers', () => {
+  it('roundtrips UTF-8 strings through base64', () => {
+    const value = 'caf\u00E9 \u2603';
+
+    expect(base64ToUtf8(utf8ToBase64(value))).toBe(value);
+  });
+
+  it('encodes arbitrary bytes to base64', () => {
+    expect(bytesToBase64(new Uint8Array([0, 65, 127, 128, 159, 255]))).toBe('AEF/gJ//');
+  });
+
+  it('counts utf8 byte length', () => {
+    expect(utf8ByteLength('hello')).toBe(5);
+    expect(utf8ByteLength('é')).toBe(2);
+  });
+
+  it('encodes latin1 bytes', () => {
+    expect(Array.from(latin1BytesFromString('password-é'))).toEqual([
+      0x70, 0x61, 0x73, 0x73, 0x77, 0x6f, 0x72, 0x64, 0x2d, 0xe9,
+    ]);
+  });
+
+  it('encodes byte arrays larger than one chunk', () => {
+    const bytes = new Uint8Array(0x90_00);
+    for (let index = 0; index < bytes.length; index++) {
+      bytes[index] = index % 256;
+    }
+
+    const decoded = Uint8Array.from(atob(bytesToBase64(bytes)), c => c.codePointAt(0) ?? 0);
+
+    expect(decoded).toEqual(bytes);
+  });
+});
diff --git a/packages/insomnia/src/utils/utf8-bytes.ts b/packages/insomnia/src/utils/utf8-bytes.ts
new file mode 100644
index 0000000000..042097483e
--- /dev/null
+++ b/packages/insomnia/src/utils/utf8-bytes.ts
@@ -0,0 +1,48 @@
+const BASE64_CHUNK_SIZE = 0x80_00;
+
+export function utf8BytesFromString(value: string): Uint8Array {
+  return new TextEncoder().encode(value);
+}
+
+export function utf8ByteLength(value: string): number {
+  return utf8BytesFromString(value).length;
+}
+
+export function utf8StringFromBytes(bytes: Uint8Array): string {
+  return new TextDecoder().decode(bytes);
+}
+
+export function latin1BytesFromString(value: string): Uint8Array {
+  const bytes = new Uint8Array(value.length);
+  for (let i = 0; i < value.length; i++) {
+    // eslint-disable-next-line unicorn/prefer-code-point -- charCodeAt for latin1 for accuracy
+    bytes[i] = value.charCodeAt(i) & 0xff;
+  }
+  return bytes;
+}
+
+export function utf8ToBase64(value: string): string {
+  return bytesToBase64(utf8BytesFromString(value));
+}
+
+export function base64ToUtf8(base64: string): string {
+  return utf8StringFromBytes(Uint8Array.from(atob(base64), c => c.codePointAt(0) ?? 0));
+}
+
+export function bytesToBase64(bytes: Uint8Array): string {
+  const chunks: string[] = [];
+  for (let offset = 0; offset < bytes.length; offset += BASE64_CHUNK_SIZE) {
+    chunks.push(String.fromCodePoint(...bytes.subarray(offset, offset + BASE64_CHUNK_SIZE)));
+  }
+  return btoa(chunks.join(''));
+}
+
+export function bodyBufferToUtf8(body: Uint8Array | string | null | undefined): string {
+  if (body == null) {
+    return '';
+  }
+  if (typeof body === 'string') {
+    return body;
+  }
+  return utf8StringFromBytes(body);
+}