A cache is a pile of files your browser keeps on your own device so it doesn’t have to download the same things twice. It makes the web feel fast. Occasionally it makes the web feel broken.

What actually gets saved

A single web page is rarely one file. It’s the page itself plus a stylesheet that decides how it looks, a few scripts that make it work, some fonts, and every image on it. That can easily be fifty separate downloads.

Most of those files are identical every time you visit. So the first time your browser fetches them, it keeps a copy and notes roughly how long that copy should be considered good for — a value the website itself suggests. On your next visit, it checks the pile first. Anything it already has, it reuses instantly instead of asking the server again.

Why it sometimes shows you the wrong thing

The website’s suggestion about how long a file stays good is a guess made in advance. If a site tells your browser “this stylesheet is good for a month” and then changes the stylesheet a week later, your browser has no reason to check. It keeps using the copy it already has, and you keep seeing the old design.

This is why the person helping you says “clear your cache” — not because they know it’s the problem, but because it’s the cheapest way to rule it out.

Refresh, hard refresh, and clearing

These are three different things, and the difference matters:

• A normal refresh (F5, or the circular arrow) reloads the page, but your browser is still allowed to reuse cached files. This is why refreshing often doesn’t help.
• A hard refresh reloads the page and tells your browser to ignore what it saved for this page. It’s fast, it’s a keyboard shortcut, and it fixes most cases. It does not affect any other website.
• Clearing the cache throws away the saved files for every site. It always works, but the next few pages you visit will load a little slower while the pile is rebuilt.

Start with a hard refresh. Clear the cache only if that doesn’t fix it.

One thing to watch out for

Most browsers put “cached images and files” in the same dialog as “cookies and other site data”, with everything ticked by default. Cookies are what keep you signed in. If you clear those too, you’ll be logged out of every website you use, which is a much bigger inconvenience than a stale page.

Untick cookies unless you actually mean to clear them.

It isn’t always the cache

A stale page can also come from a company proxy, your internet provider, the site’s own CDN, or a service worker the site installed in your browser. If you clear the cache and the page is still wrong, the problem probably isn’t on your device.