Does the webpage always display old content? F5 and Ctrl+F5 are not the same thing; I cleared all four layers of cache one by one

last month, when my home router was hacked (I wrote about the entire process in ), DNS was changed to a wild server, and an ad popped up at the bottom right corner of the webpage. I upgraded the router's firmware, changed the password, and set the DNS back to 223.5.5.5. The computer was clean on the spot. My wife's phone was still bouncing. Same WiFi, one good, one broken. I fiddled with her phone until 10 p.m. before I realized: she never checked web pages in her browser, only opened them in WeChat chat boxes—the built-in browser stored old DNS records and web pages in her own warehouse. No matter how clean the router was, it wouldn't ask.

1. First: Distinguish which layer the webpage is 'old' at

many people treat 'showing old content on a webpage' as a thing, but in reality, from the moment you type in the URL to the page pops up, there are four layers of things in between that may be 'old,' and the cleaning methods vary. First, understand this chart; everything else will be easier:

pressing F5 only touches part of the third layer; the remaining three layers are completely useless. That's why some people refresh their phones dozens of times and restart their phones, but the page is still outdated—they pressed the wrong floor.

2. Why browsers store old web pages: not laziness, but data saving

I once experimented with my own blog. The homepage is fully loaded with 1.6MB, with a total of 89 requests. The first cold opening takes just over 4 seconds; Close and reopen tabs, and it appears in 0.6 seconds. Opening F12 to check the Network panel, out of 89 requests, the Size section lists from disk cache — the browser didn't even go to the server to get it, just used the stored disk on the hard drive.

this system has two tiers. the first level is called strong caching , which can be understood as the shelf life: when the server sends files, it casually says, "This batch of images does not need to be requested again within three months" (responding to the cache-control and max-age in the header), and the browser safely stores them. If you access them again within the shelf life, they won't even ask the server. the second tier is called negotiated caching . After the expiration date, the browser takes the version number in hand and asks, "Is my version still valid?" The server checks and shows no change, only restores a 304 status code (meaning "hasn't changed"), and the browser continues to use the local version; Only when things really change do you get back 200, bring new documents.

this design is good for daily life—saving traffic and driving faster. The problem lies in 'the server side has changed, but your side is still within its shelf life.' The website updated the article, the router changed its DNS, the hijacking was removed, and the local cache was completely unaware of it.

3. Three Tips on the Computer: F5, Ctrl+F5, Incognito Window

these three are ranked by how comfortable they are.

F5 is a normal refresh . It only takes the main document seriously, and requests are marked as "verified," but supporting elements like images and styles are likely to continue using caching. So "pressing F5 and it's still the old one" is perfectly normal; it never promised to redo everything.

Ctrl+F5 is the real (on Mac, it's Cmd+Shift+R). It inserts Cache-Control: no-cache into each request header, re-requests all files from the server, and ignores all local caches. On the F12 panel, you can see a neat row of 200 caches, not a single one from disk cache—that's what you call clean.

Traceless Window is a demon-revealing mirror . The incognito window starts from scratch without any old cache, so treat it as a "standard answer": the same URL, the incognito window is new, the normal window is old. If it's confirmed as a cache issue, just clear it; The incognito window is also old, so that's not your phone's problem. Either the website hasn't updated itself, or the DNS has been redirected to the usual location, so you have to search the first and second layers.

there's also a hidden file: when the developer tools are open, right-click the browser's refresh button, and the menu will show an option called "Clear cache and force reload"—clear before requesting, even more thorough than Ctrl+F5. When I modify my blog template, I rely on it—just one quick look and a quick look.

4. The most troublesome thing on your phone is WeChat

answer to my wife's phone is here. WeChat's built-in browser (the old Android version called the X5 kernel, the new one XWeb) has its own independent cache and is completely different from the system browser. If you clear browser data a hundred times in your phone's settings, the WeChat pages remain the same.

the main way is to go into WeChat and clear it: "Me" → "Settings" → "General" → "Storage Space." Wait for it to calculate the cache size (if WeChat saves a lot, this step takes over ten seconds), then tap "Clear Cache." My wife's phone cleared out 1.9GB, then clicked the same link after cleaning, and the ads disappeared. As for the cost: this cleaning only affects the cache, doesn't touch chat history or files, but the login status of the embedded webpage drops along with it. Next time you open the login page in WeChat, you'll have to log in again.

Android has an old trick: send yourself the link debugx5.qq.com in WeChat. Clicking it opens to the kernel debugging page, where you can clear your webpage cache separately. The new version of WeChat may not keep this entry point—if you have it, use it; if not, go for the storage space route—don't get stuck on it.

mobile browser: On iOS, go to "Settings" → "Safari Browser"→ and drag down to "Clear History and Website Data"; If you only want to clear cached history, go to "Settings" → "Apps" → "Safari browser" → "Advanced" → "Website Data" → "Remove All Website Data." I recommend this option more because you can save the history for browsing old pages. On Android, Chrome is just three dots on the right side of the address bar→ "History" → "Clear browsing data." For the time range, just select "Last 1 hour." Don't just tap "All Time" and lose all login status stored for months.

5. Lessons from 301 and https: The Two Most Unfair Layers

there are two layers of "old" F5 that are completely useless because they are not files but rules recorded by the browser.

301 is a permanent redirect . When the server says, "This address has been permanently moved," the browser stores the migration record locally. After that, when you enter the old address, the browser simply follows the local record and doesn't bother with the server. Where is the pitfall? The website operator accidentally set up the wrong 301 and then changed it back; the server side had already corrected it, but the old visitor's phone still had the wrong one saved and kept jumping to the wrong location. I used to redirectory a section of my blog, forgot to remove 301 first, and after an afternoon of fussing around, I found that no matter how I changed the new address, it always reverted to the old directory—the wrong entry was recorded in my own browser. Cleanup method: Clear "Website Data" or remove the "cached images and files" box in your browsing data.

HSTS is HTTPS memory . Websites you visit can use a response header to tell the browser, "From now on, always use HTTPS to connect to me," and the browser will solder you to http:// it will revert https://. This mechanism is a great anti-hijacking feature. I wrote about the difference between http and https and I wrote about it separately in article about the login page being forced to jump to HTTPS and get stuck in a separate article. But the cost is: one day the site's HTTPS certificate is broken, and the browser refuses to let you open it with HTTP, only to report a terrifying error page—in fact, it's the memory acting up for you. To tell if "it really won't open" or "memory is at play," open the Incognito window—it doesn't consume HSTS's stored memory.

6. Finishing: Check by symptoms, followed by four steps to remove the

order is simple: first check (without trace), then force flash (Ctrl+F5), clear cache afterward, and only DNS last. The DNS layer is another world. In my article changing DNS that didn't work I wrote about three checks: flushDNS manages the system layer; The browser's own DNS cache is not their concern; the two layers need to be cleared separately. If you really want to move to the router side, I've written about modifications by brand: Xiaomi's is here, the optical modem is here. If you want to fully understand the domain resolution process, check out my using nslookup to run DNS resolution. The three-layer small notebook structure connects perfectly with this one.

back to my wife's phone: After clearing the cache on WeChat, it was clean that very night. A couple of days later, she came back to me again, saying that a mall page on the public account couldn't pay for it—this time I learned my lesson and had her copy the link and open it in the system browser. Okay. When it comes to WeChat's core, don't reason with it—switch paths for the fastest way.