Why Caching Matters
Caching stores copies of resources closer to the user, dramatically reducing load times for repeat visitors. Effective caching can reduce server load by 50-80%.
Types of Caching
Browser Caching
Stores resources on user's device.
CDN Caching
Stores resources at edge locations worldwide.
Server Caching
Stores generated content on origin server.
Application Caching
Caches database queries, API responses.
Cache-Control Headers
Key Directives
`` Cache-Control: max-age=31536000, immutable
`
| Directive | Purpose |
|-----------|---------|
| max-age | Cache duration in seconds |
| immutable | Never revalidate |
| no-cache | Revalidate every time |
| no-store | Never cache |
| public | Can be cached by CDN |
| private | Only browser can cache |
Caching Strategies by Resource Type
Static Assets (1 year)
CSS, JS, images with versioned filenames:
` Cache-Control: public, max-age=31536000, immutable
`
HTML Pages (no cache or short)
` Cache-Control: no-cache
`
API Responses (varies)
` Cache-Control: private, max-age=60
`
ETag and Last-Modified
Conditional requests for validation:
` ETag: "abc123"
Last-Modified: Wed, 21 Oct 2025 07:28:00 GMT
`
Stale-While-Revalidate
Serve stale content while fetching fresh:
` Cache-Control: max-age=3600, stale-while-revalidate=86400
``
Audit your caching strategy with our free performance tool.