diff --git a/packages/preview-process/src/parts/GenerateEtag/GenerateEtag.ts b/packages/preview-process/src/parts/GenerateEtag/GenerateEtag.ts
new file mode 100644
index 0000000..96a2f34
--- /dev/null
+++ b/packages/preview-process/src/parts/GenerateEtag/GenerateEtag.ts
@@ -0,0 +1,7 @@
+import { createHash } from 'node:crypto'
+
+export const generateEtag = (content: string): string => {
+  const hash = createHash('sha1')
+  hash.update(content)
+  return `W/"${hash.digest('hex')}"`
+}
diff --git a/packages/preview-process/test/GenerateEtag.test.ts b/packages/preview-process/test/GenerateEtag.test.ts
new file mode 100644
index 0000000..0054518
--- /dev/null
+++ b/packages/preview-process/test/GenerateEtag.test.ts
@@ -0,0 +1,23 @@
+import { expect, test } from '@jest/globals'
+import * as GenerateEtag from '../src/parts/GenerateEtag/GenerateEtag.ts'
+
+test('generateEtag - generates weak etag from content', () => {
+  const content = 'test content'
+  const etag = GenerateEtag.generateEtag(content)
+  expect(etag).toMatch(/^W\/"[a-f0-9]+"$/)
+})
+
+test('generateEtag - generates different etags for different content', () => {
+  const content1 = 'content 1'
+  const content2 = 'content 2'
+  const etag1 = GenerateEtag.generateEtag(content1)
+  const etag2 = GenerateEtag.generateEtag(content2)
+  expect(etag1).not.toBe(etag2)
+})
+
+test('generateEtag - generates same etag for same content', () => {
+  const content = 'same content'
+  const etag1 = GenerateEtag.generateEtag(content)
+  const etag2 = GenerateEtag.generateEtag(content)
+  expect(etag1).toBe(etag2)
+})