Website caching means saving something that has already been generated so it can be reused faster next time. Instead of asking the server to rebuild the same page, image, stylesheet, or database query for every visitor, a cached copy can be served with less work.
Caching is one of the easiest ways to improve perceived speed, but it can also cause confusion. If you update a page and still see the old version, cache is often the reason. The trick is knowing which cache you are dealing with.
Browser Cache
Browser cache lives on the visitor's device. It stores files such as images, CSS, JavaScript, fonts, and sometimes HTML. When someone visits another page on the same site, the browser may reuse files it already downloaded.
This is good for speed because the visitor does not need to download the same logo, stylesheet, and script files repeatedly. It can be confusing after design changes because your browser may keep showing an old stylesheet until the cache expires or is cleared.
Page Cache
Page cache stores the finished HTML of a page. On a WordPress site, this can avoid running PHP, loading plugins, and querying the database for every anonymous visitor. For brochure sites and blogs, page cache is often the biggest win.
Page cache must be used carefully on pages that change per user. Account areas, baskets, checkout pages, and logged-in dashboards should usually be excluded or handled with rules designed for the application.
Object Cache
Object cache stores smaller pieces of application data, often database query results. WordPress can use object caching to avoid repeating expensive database work. Redis is a common persistent object cache for WordPress and WooCommerce.
Object cache is most useful on dynamic sites: WooCommerce stores, membership sites, directories, forums, and sites with heavy plugin queries. It is not a replacement for page cache; the two solve different problems.
Opcode Cache
PHP opcode cache stores compiled PHP code in memory. This reduces repeated PHP parsing work and is usually enabled at the server level. Most website owners do not manage it day to day, but it is an important part of PHP performance.
CDN Cache
A CDN cache stores assets, and sometimes whole pages, at locations closer to visitors. Cloudflare and similar services can cache images, scripts, stylesheets, and selected pages at the edge.
A CDN helps most when visitors are spread across different regions or when a site serves many static assets. It is less useful if every page is highly personalised and cannot be cached.
What Should Not Be Cached?
- Checkout pages.
- Basket or cart pages.
- Logged-in account areas.
- Admin dashboards.
- Pages with one-time tokens, payment callbacks, or form confirmation states.
These pages can still use some caching for static assets, but the final HTML should usually remain dynamic so visitors see the right account, order, or form state.
When Should You Clear Cache?
Clear cache after changing a theme, editing CSS, updating navigation, publishing major layout changes, changing product prices, or fixing content that must appear immediately. For ordinary blog posts, your publishing tool may clear the right cache automatically.
Do not clear every cache constantly. If cache is cleared too often, visitors lose the speed benefit and the server has to rebuild pages repeatedly.
How to Tell If Cache Is Working
- Load the same page twice and compare the response time.
- Check whether static files return cache headers.
- Use your caching plugin's status tools if it has them.
- Use browser developer tools to see whether files are loaded from disk, memory, or the network.
- Test while logged out, because many systems bypass cache for logged-in users.
Common Caching Problems
- Old design still showing: browser cache, CDN cache, or minified CSS cache may need clearing.
- Basket behaves strangely: checkout or cart pages may be cached incorrectly.
- Forms fail after submission: page cache may be storing a token or confirmation state.
- Admin changes do not appear: the site may have multiple cache layers, such as plugin cache plus CDN cache.
TekLan Hosting Notes
For WordPress, start with page caching and sensible image optimisation. For busy dynamic WordPress sites, consider Redis object cache as the next step. For sites with visitors outside the UK, a CDN can help with static assets and global response times.
Useful next reads: Redis Object Cache for WordPress Explained, How to Check if a Website Is Using Cache, and Why Your Website Is Slow.
