Clearing the DNS cache

"Flush your DNS" is standard advice and it is usually given incompletely, which is why it so often fails to work. There is no single DNS cache. There are four layers of them, and an answer cached in a layer you did not clear will be served straight back to you.

In the order a query travels:

1. The browser's own cache - Chrome and Firefox both keep one, independent of the system.
2. The operating system cache - What "flush DNS" usually means.
3. The router cache - Most home routers cache, some for a long time.
4. The resolver's cache - Your ISP's or a public resolver's. You cannot touch this one.

Windows

Open Command Prompt or PowerShell as Administrator:

ipconfig /flushdns

You should see "Successfully flushed the DNS Resolver Cache." To inspect what is cached before clearing:

ipconfig /displaydns

If flushing does not help, restart the DNS Client service, which occasionally gets stuck:

net stop dnscache
net start dnscache

macOS

The command has changed across versions. On any release from Sequoia back to Yosemite:

sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder

Both halves matter - The first clears the directory service cache, the second restarts the multicast DNS responder. There is no confirmation message; silence means it worked.

Linux

Depends on what is running. With systemd-resolved, which is the default on most modern distributions:

sudo resolvectl flush-caches

With dnsmasq:

sudo systemctl restart dnsmasq

With nscd:

sudo systemctl restart nscd

If none of those exist, your system probably is not caching at all and queries go straight to the configured resolver.

iOS and iPadOS

No command and no setting. Two options:

• Airplane mode on, wait ten seconds, off. Usually enough, and non-destructive.
• Reset Network Settings (Settings → General → Transfer or Reset → Reset). Definitely clears it, and also forgets every saved Wi-Fi password - So have them to hand.

Android

Same situation. Airplane mode is the gentle option. Otherwise clear the browser's own cache, or restart the device.

Chrome on Android has its own DNS cache reachable at chrome://net-internals/#dns, which is worth trying before anything system-wide.

The browser caches everyone forgets

This is the step that makes the difference when the system flush "did not work".

Chrome and other Chromium browsers: Go to chrome://net-internals/#dns and press Clear host cache. Then chrome://net-internals/#sockets and Flush socket pools - An existing pooled connection to the old address will otherwise keep being reused.

Firefox: about:networking#dns, then Clear DNS Cache.

Safari: No separate cache; quitting and reopening the application is sufficient.

The router

Most home routers cache DNS, and some hold negative answers for a very long time. A restart clears it. Power off for thirty seconds rather than using a quick reset - A brief cycle sometimes preserves state you were trying to discard.

This is genuinely one of the few problems where "have you tried turning it off and on again" is the correct diagnosis rather than a joke.

The one you cannot clear

Your ISP's resolver caches on its own schedule, governed by the TTL on each record, and you have no way to influence it. If a record has changed and your ISP is still serving the old one, your options are to wait or to stop using that resolver.

Switching your device to a public resolver bypasses the problem instantly, which is why it is the recommendation whenever a DNS change is not propagating. Here is how to do it on every platform.

Negative caching

Worth repeating because it explains the most confusing version of this problem. DNS caches "does not exist" answers as well as real ones, for a duration set in the domain's SOA record.

So if you visited a domain in the window before its records went live, you may hold NXDOMAIN for anywhere from minutes to hours - And every retry returns the cache rather than asking again. The site works perfectly for everyone else. Clearing every cache you control is the fix, and if the negative answer is held at the resolver, switching resolvers is the only quick route.

A note on propagation

"DNS propagation" is a slightly misleading phrase - Nothing propagates. Records are published immediately at the authoritative nameservers, and what takes time is existing caches expiring. The record's TTL determines how long.

Which means: If you know you are about to change a record, lower its TTL a day beforehand. Doing it after the change achieves nothing, because everyone already holds the old value with the old TTL.