1---
2title: Avoid Duplicate Serialization in RSC Props
3impact: LOW
4impactDescription: reduces network payload by avoiding duplicate serialization
5tags: server, rsc, serialization, props, client-components
6---
7 
8## Avoid Duplicate Serialization in RSC Props
9 
10**Impact: LOW (reduces network payload by avoiding duplicate serialization)**
11 
12RSC→client serialization deduplicates by object reference, not value. Same reference = serialized once; new reference = serialized again. Do transformations (`.toSorted()`, `.filter()`, `.map()`) in client, not server.
13 
14**Incorrect (duplicates array):**
15 
16```tsx
17// RSC: sends 6 strings (2 arrays × 3 items)
18<ClientList usernames={usernames} usernamesOrdered={usernames.toSorted()} />
19```
20 
21**Correct (sends 3 strings):**
22 
23```tsx
24// RSC: send once
25<ClientList usernames={usernames} />
26 
27// Client: transform there
28'use client'
29const sorted = useMemo(() => [...usernames].sort(), [usernames])
30```
31 
32**Nested deduplication behavior:**
33 
34Deduplication works recursively. Impact varies by data type:
35 
36- `string[]`, `number[]`, `boolean[]`: **HIGH impact** - array + all primitives fully duplicated
37- `object[]`: **LOW impact** - array duplicated, but nested objects deduplicated by reference
38 
39```tsx
40// string[] - duplicates everything
41usernames={['a','b']} sorted={usernames.toSorted()} // sends 4 strings
42 
43// object[] - duplicates array structure only
44users={[{id:1},{id:2}]} sorted={users.toSorted()} // sends 2 arrays + 2 unique objects (not 4)
45```
46 
47**Operations breaking deduplication (create new references):**
48 
49- Arrays: `.toSorted()`, `.filter()`, `.map()`, `.slice()`, `[...arr]`
50- Objects: `{...obj}`, `Object.assign()`, `structuredClone()`, `JSON.parse(JSON.stringify())`
51 
52**More examples:**
53 
54```tsx
55// ❌ Bad
56<C users={users} active={users.filter(u => u.active)} />
57<C product={product} productName={product.name} />
58 
59// ✅ Good
60<C users={users} />
61<C product={product} />
62// Do filtering/destructuring in client
63```
64 
65**Exception:** Pass derived data when transformation is expensive or client doesn't need original.
66