How to Fix React Key Warning in AI-Built Apps
React warns about missing or incorrect keys in lists, causing unpredictable UI behavior. AI-generated code often uses array indexes as keys or omits them entirely.
Error messages you might see
Warning: Each child in a list should have a unique "key" prop.Warning: Encountered two children with the same key. Keys should be unique.Why this happens in AI-generated code
Using array index as key
AI uses `.map((item, index) => <Item key={index} />)` which breaks when items are reordered or deleted.
Missing keys on mapped elements
AI forgets to add the key prop entirely on dynamically rendered list items.
Duplicate keys from data
The data source has duplicate IDs, or AI generates keys from non-unique fields like `name`.
How to fix it
Use stable unique identifiers
Use database IDs or other stable, unique values: `items.map(item => <Item key={item.id} />)`. Never use index for dynamic lists.
Generate unique keys when data lacks IDs
Use `crypto.randomUUID()` at data creation time (not render time) to generate stable keys for items without natural IDs.
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Frequently asked questions
Is using index as key always bad?
It's safe only for static lists that never reorder or filter. For any dynamic list, use a stable unique identifier.
Why does React need keys?
Keys help React identify which items changed, were added, or removed. Without proper keys, React may reuse the wrong component instances.
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