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Flush DNS command

Published 19 September 2026

The flush DNS command for each operating system is below. Then the part that trips people up, and the reason so many Linux guides are useless: most Linux systems have no DNS cache to flush at all. The commands you find still run, still print nothing, and still change nothing, because there was never anything there.

The commands

On macOS run both lines; they clear different caches and neither prints anything on success.

Windows

ipconfig /flushdns in Command Prompt or PowerShell. Mind the slash: ipconfig flushdns without one prints the usage text rather than flushing anything, which is easy to skim past as success.

Verify with ipconfig /displaydns, which should be all but empty afterwards. Two failures are common and mean different things: "The requested operation requires elevation" needs an administrator prompt, and "Could not flush the DNS Resolver Cache" usually means the DNS Client service is stopped.

The full version, including the negative cache that makes a record you just created keep reporting "no such name": ipconfig /flushdns explained.

macOS

sudo dscacheutil -flushcache
sudo killall -HUP mDNSResponder

Both are needed. Check with dscacheutil -statistics: the entry counts drop to nothing after a successful flush. Older guides suggesting lookupd or discoveryutil are for macOS versions long gone; those binaries no longer exist.

The full version: clearing the DNS cache on a Mac.

Linux: find out whether you have a cache first

This is where most advice goes wrong. glibc does not cache DNS. A plain Linux install (many servers, plenty of desktops) resolves every name afresh and holds nothing between lookups. There is no cache, so there is nothing to flush, and every command you try will appear to do nothing because it genuinely did nothing.

Search for a flush DNS Linux command and you get a list of daemons, usually nscd, dnsmasq and systemd-resolved, offered as though one of them must be yours. Most guides to clear DNS cache Linux skip the question that decides everything: is anything caching at all? The flush DNS Ubuntu answer is usually systemd-resolved on a desktop and nothing at all on a minimal server.

Caching on Linux only happens if something was installed to do it. Find out which, before running anything:

systemctl is-active systemd-resolved   # the common one on modern distros
systemctl is-active nscd
systemctl is-active dnsmasq

systemd-resolved

The usual answer on Ubuntu 18.04 and later, Fedora, and most current desktops. This is what people mean by flush DNS on Ubuntu:

sudo resolvectl flush-caches

On older releases the same job was sudo systemd-resolve --flush-caches, which still works on some systems and is gone on others. Verify either with:

resolvectl statistics

The cache hit and miss counters reset. That is the confirmation: worth having, because a successful flush and a command that silently did nothing look identical.

nscd

The old Name Service Cache Daemon. Present on some servers, absent on most modern desktops:

sudo nscd -i hosts        # invalidate just the hosts cache
sudo systemctl restart nscd

dnsmasq

Common on routers and on some NetworkManager configurations, where it acts as a local forwarder:

sudo systemctl restart dnsmasq

BIND, if the box is a resolver

sudo rndc flush              # everything
sudo rndc flushname example.com   # one name

Flushing a cache does not validate the daemon or install a security update. If you operate the server, the BIND DNS server patching guide covers version checks, configuration validation and one-node-at-a-time verification.

If none of them are running

Then you have your answer, and it is a useful one: the stale record is not on this machine. It is in your browser, your router, or your upstream resolver, and only one of those is yours to clear.

Why flushing so often changes nothing

Your machine is one cache among several, and the flush DNS command reaches exactly one of them:

That last row decides most cases. Change a record with a one-hour TTL and the public resolvers serve the old value for up to an hour regardless of what you type. You are not failing to flush: you are waiting, and the only question is how long.

The browser has its own cache

Chrome and Edge keep a host cache independent of the operating system, and many installs now use DNS over HTTPS, resolving names directly to a provider without asking the OS at all. When that is on, no flush DNS command can help, because the browser was never using the cache you cleared.

Clear it at chrome://net-internals/#dns or edge://net-internals/#dns. The tell is quick: if nslookup or dig returns the right address and the browser still goes somewhere else, stop flushing the system cache.

What flushing is not for

• A name that never resolved. Flushing clears wrong answers; it cannot invent a right one. Check the record exists first.
• Speed. An empty cache is briefly slower, not faster.
• "Propagation." There is no such process: only TTLs, and other people's resolvers honouring them.
• Connectivity. If nothing resolves at all, the question is whether you can reach a resolver, which is a different fault. See no route to host for telling refused, timed out and unreachable apart.