The Expert WordPress Guide to Clearing Your DNS Cache

As a webmaster with over 15 years of experience running WordPress sites, I can‘t stress enough the importance of clearing your DNS cache when needed. A stale cache can wreak havoc by directing you to the wrong server environment. Flushing it forces your device to reobtain fresh DNS records from nameservers.

In this expanded guide, I‘ll cover everything from a deep dive into how DNS works to WordPress-specific use cases for cache clearing to pro tips for trouble-free DNS management. Let‘s get started!

A Beginner‘s Guide to DNS Caching

Before we flush caches, we need to understand how DNS works and why caching is so vital for fast performance.

DNS is the internet‘s directory that translates human-friendly domain names like example.com into machine-friendly IP addresses like 93.184.216.34. This conversion enables routing.

When you type a URL into your browser, here‘s what happens behind the scenes:

1. Your device checks its local DNS cache for a saved record mapping the domain to an IP.

2. If found, the IP is retrieved from cache. No DNS lookup occurs.

3. If not cached, your DNS resolver (usually your router) queries a DNS server to find the IP.

4. The IP is then returned and saved in your cache for future requests.

The Need for Speed

On average, a DNS cache can speed up access by 400% or more compared to uncached lookups.

For example, say an uncached DNS request takes 40ms to receive a reply from your ISP‘s server.

But a cached request takes just 10ms to get the IP from your local device‘s cache – 4x faster!

Over thousands of requests, these milliseconds add up to seconds of saved time thanks to caching. Frequent and repeated site visits benefit the most from cached DNS thanks to lightning fast IP retrieval.

DNS Record Types

DNS servers maintain various types of records that get cached locally:

• A: Maps a domain name to an IPv4 address

• AAAA: Maps a domain to an IPv6 address

• CNAME: Points a domain alias to the real domain name

• MX: Defines mail servers for a domain

• NS: Identifies DNS nameservers for a domain

• TXT: Provides extra text information about a domain

Controlling Cache Times

Domains can configure a TTL (Time To Live) that sets the max cache duration for DNS records in seconds:

• Short TTL = Faster propagation but slower repeat access

• Long TTL = Slower propagation but faster repeat access

The default TTL is typically 8,600 seconds or 2 hours. Clearing your cache overrides the TTL.

Now that we‘ve got a handle on why DNS caching matters, let‘s move on to when and how to flush it.

When to Clear Your DNS Cache

As mentioned earlier, the DNS cache is designed to speed up site revisits by avoiding repetitive lookups.

However, sometimes the cache can grow stale and continue pointing your device to outdated IP addresses. Common scenarios where clearing your DNS cache is recommended:

Migrating WordPress to a New Host

When moving hosts, the domain name may point to the old host IP for hours or days after the switch. This is because the TTL controls cache times across recursors worldwide.

Flushing your local cache forces your browser to query nameservers again to get the right location.

Updating the IP Address of a Domain

Similarly, if you update your domain‘s A record to a new IP, clearing the DNS cache will ensure your device starts using the updated IP immediately.

Changing WordPress Domain Names

If you switch your WP site to a different domain name, local DNS caches may still direct traffic to the old domain. Flushing fixes this.

Modifying DNS Settings

Made a change to your domain‘s DNS configuration like adding an MX record or new A record? Flushing DNS retrieves the latest settings.

Speeding Up Site Access

If a WordPress site suddenly becomes inaccessible or starts loading slowly, clearing your browser cache and DNS cache can accelerate access.

Bypassing Intermediary Caches

CDNs and load balancers also cache DNS locally. When troubleshooting, flush their DNS in addition to your own computer‘s cache.

As a rule of thumb, clear your DNS cache anytime you modify DNS records or migrate WordPress sites. This circumvents outdated cached records.

Now let‘s look at how to flush the DNS cache on different operating systems.

Clearing the DNS Cache in Windows

Windows PCs store DNS records in a cache database that can be flushed with just a few clicks:

1. Open the Command Prompt app by typing "cmd" in the taskbar search box and pressing Enter.

2. Type ipconfig /flushdns and press Enter to wipe all DNS entries cached by Windows.

That‘s all there is to it! Windows will now re-request DNS data when you visit sites.

PowerShell Alternative

You can also use PowerShell to flush the Windows DNS cache with this command:

Clear-DnsClientCache

Reload Open Browser Windows

Make sure to reload any open browser tabs and windows to force new DNS queries after clearing Windows DNS cache.

Flushing DNS Cache on macOS

macOS also maintains its own local DNS cache that needs clearing apart from the browser cache. Here‘s how:

1. Launch the Terminal app from Finder > Applications > Utilities.

2. Type sudo killall -HUP mDNSResponder and enter your password when prompted.

3. The DNS cache is now flushed system-wide. Reopen browser windows to utilize fresh cache.

Alternatively, you can use this Terminal command which also achieves the same effect:

sudo dscacheutil -flushcache 

That‘s all you need to do to empty DNS cache on macOS. Next let‘s look at clearing browser caches.

How to Clear the DNS Cache in Chrome

In addition to the OS cache, browsers also cache DNS records locally for performance.

To flush Chrome‘s DNS cache:

1. Type chrome://net-internals/#dns in the address bar and press Enter.

2. Click the "Clear host cache" button to wipe all DNS records cached by Chrome.

Chrome will now retrieve new DNS entries for sites you visit.

repeating the steps above for Firefox, Safari, Edge, etc to clear the browser DNS cache in each one after making DNS changes.

Best Practices for Trouble-Free DNS Management

Here are some pro tips from my years as a webmaster for smooth DNS operations when managing WordPress sites:

• Temporarily reduce DNS TTLs globally before migrating domains or making DNS configuration changes. This allows new settings to propagate faster.

• Disable DNS caching on your local network adapter if downtime must be minimized when shifting DNS settings. This forces immediate queries vs using cache.

• Always flush your local DNS cache before testing DNS changes – don‘t rely on the TTL.

• After modifying DNS records, use a propagation checking tool to validate worldwide distribution of new settings.

• Preemptively clear browser and OS DNS caches before cutover events like domain migrations to avoid any caching delays.

• For sites using CDNs or load balancers, clear their DNS cache too when troubleshooting issues. Don‘t rely solely on flushing your own PC‘s cache.

Following best practices like the ones above can help avoid DNS caching problems when managing WordPress sites.

In Closing

I hope this expanded DNS cache guide gives you a deeper look into how DNS works and when clearing your cache is needed. Flushing stale DNS entries is crucial for accessing site changes immediately during events like WordPress migrations.

Let me know if you have any other questions! I‘m happy to provide additional details from my 15 years of experience managing DNS for websites.