1# Runtime Selection
2 
3## Use Node.js Runtime by Default
4 
5Use the default Node.js runtime for new routes and pages. Only use Edge runtime if the project already uses it or there's a specific requirement.
6 
7```tsx
8// Good: Default - no runtime config needed (uses Node.js)
9export default function Page() { ... }
10 
11// Caution: Only if already used in project or specifically required
12export const runtime = 'edge'
13```
14 
15## When to Use Each
16 
17### Node.js Runtime (Default)
18 
19- Full Node.js API support
20- File system access (`fs`)
21- Full `crypto` support
22- Database connections
23- Most npm packages work
24 
25### Edge Runtime
26 
27- Only for specific edge-location latency requirements
28- Limited API (no `fs`, limited `crypto`)
29- Smaller cold start
30- Geographic distribution needs
31 
32## Detection
33 
34**Before adding `runtime = 'edge'`**, check:
351. Does the project already use Edge runtime?
362. Is there a specific latency requirement?
373. Are all dependencies Edge-compatible?
38 
39If unsure, use Node.js runtime.
40