🧠 What is a Web Cache?
A web cache is like a middleman between a website’s main server (origin server) and the user’s browser.
When you open a website, your browser requests files (like images, CSS, or JavaScript). This request first goes to the cache instead of directly to the server.
🔹 How it Works:
- If the cache already has a copy of the requested file (called a cache hit), it sends it directly to the user — making the site load faster.
- If the cache does not have the file (called a cache miss), it forwards the request to the original server.
The server then sends the response back to the cache, which may store it for future use before sending it to the user.
⚙️ Why Web Caching is Important
Web caching helps websites load faster and reduces load on the main server.
Most websites today use CDNs (Content Delivery Networks) — a network of servers around the world that store cached versions of website content.
This means when someone visits a site, they get the content from the nearest server, improving speed and performance.
🔑 What are Cache Keys?
When the cache receives a request, it needs to decide whether it already has a stored response for it.
It does this by generating a cache key — a unique identifier created using parts of the request such as:
- URL path
- Query parameters
- Headers
- Content type
If two requests have the same cache key, the cache treats them as the same and delivers the stored response.
(In advanced security topics, attackers can manipulate cache keys to perform something called web cache poisoning, but that’s a separate concept.)
📜 What are Cache Rules?
Cache rules tell the cache what it can store and for how long.
Usually:
- Static files (like images, CSS, JS) are cached because they rarely change.
- Dynamic content (like user profiles or dashboards) isn’t cached since it may contain personal or constantly updated data.
These rules help ensure users get the right balance between speed and freshness of data.
Common Types of Cache Rules:
- Static File Extension Rules
Cache files based on their extensions — for example,.css,.js,.jpg. - Static Directory Rules
Cache all files inside specific folders like/static/or/assets/. - File Name Rules
Cache specific files that don’t change often, such asrobots.txtorfavicon.ico.
Some caching systems may also use custom rules based on URL parameters or special conditions.
🚨 Web Cache Deception
Attackers sometimes try to trick caching systems by exploiting how cache rules are applied.
If not properly configured, sensitive dynamic content (like user info) could get cached and exposed to others.
That’s why understanding how cache rules and cache keys work is important for web security.