What Is DNS Cache? Definition, Safety, and How to Flush It

Anyone who has typed a web address and waited for a page to load has encountered the DNS cache—a behind-the-scenes shortcut that saves time by remembering where websites live. This temporary storage system, which maps domain names to IP addresses, makes repeated visits faster but also raises questions about privacy and security. Understanding how to check and clear your DNS cache can help you troubleshoot connection issues and stay in control of your data.

Average DNS cache size on Windows: 10 MB · Default TTL for DNS records: 3600 seconds (1 hour) · Time saved per DNS lookup with cache: 10–100 ms · Number of DNS cache entries on a typical device: Hundreds to thousands

What is DNS cache and how does it work?

Every time you visit a website, your device performs a DNS lookup to translate the human-readable domain name (like example.com) into a machine-readable IP address. The DNS cache stores that mapping locally so the next time you visit the same site, the lookup can be skipped—saving 10–100 milliseconds per request (KeyCDN, a content delivery network).

How DNS caching improves browsing speed

• Reduces the number of queries sent to external DNS servers, lowering network latency.
• Prevents redundant lookups for frequently visited domains, making page loads feel snappier.
• Helps websites load faster on slower connections by avoiding repeated round trips.

The pattern: DNS cache is a local copy of the phonebook of the internet, and using it avoids redialing directory assistance every time.

The role of TTL (time-to-live)

Each cached DNS record includes a TTL—a timer set by the domain owner that tells the cache how long to keep the entry before discarding it and re-querying. The default TTL is often 3600 seconds (one hour), but it can range from a few minutes to several days (Microsoft Learn, the PowerShell documentation).

What this means: TTL is the cache’s expiration date, and understanding it helps you decide when flushing might be needed—without it, you may keep hitting a dead or wrong address for hours.

Is it safe to clear DNS cache?

Yes, clearing your DNS cache is safe. It does not delete any personal files, passwords, bookmarks, or browsing history. The process, sometimes called flushing, simply removes the temporary IP address records stored by your device or browser (Apple Support, the official macOS guidance).

When flushing DNS cache is recommended

• After a website changes its IP address and you still see the old version or an error.
• When you encounter “website not found” errors that other devices on the same network don’t see.
• After troubleshooting a malware or cache poisoning incident to remove any malicious entries.

Potential temporary slowdown after clearing

Immediately after flushing, your device has no cached IP records, so the next few domain lookups will require full DNS queries—adding a small delay (10–100 ms each) until the cache rebuilds. This is normally unnoticeable in practice (DigiCert, the certificate authority FAQ).

The implication: Flushing is safe and often helpful, but don’t expect it to solve every connectivity issue or to boost your privacy on its own.

How do I check my DNS cache?

Checking your DNS cache lets you see what domain-to-IP mappings are currently stored. The method depends on your operating system. Two rows illustrate the dominant patterns.

Check DNS cache on Windows using Command Prompt

1. Open Command Prompt as Administrator (right-click Start menu, choose “Command Prompt (Admin)”).
2. Type ipconfig /displaydns and press Enter.
3. Scroll through the list of cached records showing domain name, TTL, and IP address.

Microsoft provides the ipconfig /displaydns command as a built-in tool for viewing the DNS client cache (Microsoft Learn, the Windows networking documentation).

Check DNS cache on macOS using Terminal

1. Open Terminal (Finder > Go > Utilities > Terminal).
2. Type sudo killall -INFO mDNSResponder (for macOS 10.10.4+) and press Enter.
3. For older versions, use sudo dscacheutil -cachedump (UCSF IT, the university tech support guide).

View DNS cache on Android and iPhone

Mobile devices—both Android and iOS—do not expose a built-in command to view the DNS cache directly. On Android, users typically need root access or a third-party app. On iPhone, restarting the device effectively clears the cache but viewing it is not possible with stock tools (Apple Support Community, user discussion).

The catch: Windows and Mac users have straightforward commands, but mobile users are left with limited visibility. If you suspect a stale cache on your phone, a restart is the simplest workaround.

Does clearing DNS cache delete history?

No—clearing your DNS cache does not delete browser history, bookmarks, saved passwords, or any other personal data. It only removes the temporary IP address records stored from previous DNS lookups (KeyCDN, the CDN performance resource).

Difference between DNS cache and browser history

• Browser history: A list of URLs you visited, stored by the browser (Chrome, Firefox, etc.). Clearing it removes the visible log but not DNS cache entries.
• DNS cache: A system-level store of IP addresses, managed by the operating system or browser. It contains no URLs, passwords, or timestamps.

What clearing DNS cache actually removes

It deletes only the mapping data—for example, that google.com equals 142.250.190.78. The browser still retains its own cache of page resources, cookies, and history separately (Google Public DNS documentation, the DNS service guide).

The pattern: DNS cache and browser history live in different houses on the same street. Clearing one has no effect on the other, so you can flush without worry.

Should I enable DNS cache?

In nearly all cases, yes. DNS caching is enabled by default on every major operating system and browser because the performance benefits—reduced lookup times and lower server load—are substantial. However, there are edge cases where disabling or flushing is advisable.

Pros of keeping DNS cache enabled

• Faster browsing speeds: repeated lookups skip the query step altogether.
• Reduced network traffic: fewer DNS queries mean less load on your internet connection and public DNS servers.
• Better user experience: page loads feel instantaneous for sites you visit regularly.

Cons of enabling DNS cache

• Stale data risk: if a site’s IP changes before TTL expires, you may hit an old address.
• Cache poisoning vulnerability: an unsecured cache can be manipulated to redirect traffic to malicious sites.
• Minor memory usage: the cache occupies a few megabytes of RAM, though this is negligible on modern devices.

When to disable or flush DNS cache

Disabling DNS cache entirely is rarely necessary. The standard practice is to flush the cache when you encounter connectivity problems after a site move, or as a troubleshooting step. Security experts from DigiCert note that periodic flushing is a maintenance step for stale resolution rather than a general security control (DigiCert, the certificate authority FAQ).

How to Flush DNS Cache (Windows, Mac, Chrome)

Flushing the DNS cache is a straightforward process. The commands vary by platform, but the principle is the same: delete the local cache so the next lookup fetches fresh records.

Flush DNS cache on Windows

1. Open Command Prompt as Administrator.
2. Type ipconfig /flushdns and press Enter.
3. You should see the confirmation message: “Successfully flushed the DNS Resolver Cache.”

Microsoft’s Clear-DnsClientCache PowerShell cmdlet does the same thing and is equivalent to ipconfig /flushdns (Microsoft Learn, the Windows PowerShell documentation).

Flush DNS cache on macOS

1. Open Terminal.
2. For macOS 10.10.4 and later (including Sonoma 14), type sudo killall -HUP mDNSResponder and press Enter.
3. Enter your admin password when prompted, then press Return. No confirmation message appears, but the cache is cleared instantly.

Apple’s official page provides version-specific commands; for older systems like El Capitan 10.11, the command sudo dscacheutil -flushcache was used (Apple Support, the macOS DNS reset guidance).

Flush DNS cache in Google Chrome

1. Type chrome://net-internals/#dns in the address bar and press Enter.
2. Click the “Clear host cache” button. This removes Chrome’s own DNS cache, separate from the system cache.

Microsoft’s support content confirms that Edge has a similar internal cache accessible via edge://net-internals/#dns (Microsoft Q&A, the Windows support forum).

The pattern: three platforms, one goal. After flushing, your device will rebuild the cache gradually over the next few minutes.

“DNS cache is temporary storage of DNS lookup results on your device or browser. It maps domain names to IP addresses to avoid repeated queries to a DNS server.”

— Akamai glossary, the global CDN and cloud provider

“To flush the DNS cache on Windows, open Command Prompt and run ipconfig /flushdns. This clears the local resolver cache.”

— Microsoft support documentation, the Windows operating system developer

“Google Public DNS users can flush their cache by visiting the control panel, but local system cache must be cleared separately using operating system commands.”

— Google Public DNS documentation, the public DNS resolver service

“DNS cache is a temporary database of DNS records that a computer or browser maintains. Flushing it forces the system to query the DNS server for the latest information.”

— KeyCDN support article, the content delivery network resource

The stakes are practical rather than dramatic. For everyday users, leaving DNS cache on is the right default. For anyone who encounters a “website not found” error after a site migration or sees a suspicious redirect, the first step should be a two-second flush command. For system administrators managing multiple machines, scripting the flush across endpoints ensures stale records don’t cause intermittent outages.

For a detailed breakdown of how DNS cache works and whether it’s safe to clear, see this DNS cache definition and safety guide.

Frequently asked questions