Is the local DNS cache causing access errors? How to clean and reset it

　　In our daily browsing, we sometimes encounter situations where a website is accessible, but our computer displays "Unable to connect to server" or "DNS resolution error." However, everything works fine on a different device or network. This phenomenon is often related to the local DNS cache. The DNS cache is a temporary resolution record saved by the operating system and browser to speed up website access. However, when this cache expires or is incorrectly recorded, it can lead to access failures, abnormal page redirects, and even security risks. Understanding how the DNS cache works and how to properly clear and reset it is crucial to maintaining a smooth network.

　　DNS is the internet's "address book," responsible for translating domain names we enter (such as example.com) into corresponding server IP addresses. To avoid querying the DNS server every time we access a website, the system stores a local cache. This cache allows the next visit to the same website to be directly retrieved, significantly improving response speeds. However, this convenience can also lead to problems. When a website changes servers, domain name resolution changes, the network environment adjusts, or system updates or malware modify DNS settings, the local cache may store outdated or incorrect resolution results. The result is that users may experience webpage inaccessibility, incorrect redirects, or even unofficial, forged websites.

　　For example, on Windows, when a browser cannot access certain websites while other websites function normally, a DNS cache anomaly is often suspected. Common error messages include "DNS_PROBE_FINISHED_NXDOMAIN" or "Server DNS address could not be found." Clearing the DNS cache often restores access immediately. The clearing process is simple: simply open a command prompt (CMD) as an administrator and enter the following command:

ipconfig /flushdns

　　After executing this command, the system will prompt "Successfully flushed the DNS Resolver Cache," indicating that the DNS cache has been successfully cleared. At this point, if you try to access a website again, the system will re-request resolution from the DNS server to obtain the latest IP address.

　　Clearing the DNS cache in macOS is equally simple, but the command is slightly different. You can open Terminal and enter the following command:

sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder

　　Enter the administrator password and press Enter. The system will restart the DNS service to refresh the cache. For Linux users, you can use the command according to the system version:

sudo systemd-resolve --flush-caches

　　or:

sudo /etc/init.d/nscd restart

　　After this is complete, the DNS cache will be cleared.

　　Sometimes, in addition to the system-level DNS cache, the browser itself also stores some resolution records. Modern browsers like Chrome and Edge, in particular, maintain independent DNS caching mechanisms to improve loading speeds. If clearing the system cache doesn't resolve the issue, try clearing your browser's DNS records. For example, in Chrome, enter:

chrome://net-internals/#dns

　　After opening, click "Clear host cache" to clear the cache. For other browsers, such as Firefox, you can also clear the network cache and DNS data through Settings or Privacy. After clearing, it's recommended to close and reopen the browser to ensure the new settings take effect.

　　In addition to clearing the cache, checking your DNS server settings is also essential. Sometimes, resolution failures aren't caused by cache issues, but rather by abnormal DNS server responses or misconfiguration. Try switching to a public DNS server to test whether normal access is restored. To change the DNS server in Windows, open "Network and Sharing Center," click the network connection you're using → Properties → Select "Internet Protocol Version 4 (TCP/IPv4)" → Manually set the DNS server address. Save the settings and then clear the cache again; this usually resolves most access issues.

　　Note that some internet security software or ad blockers can interfere with DNS resolution. If clearing the cache and changing the DNS server still doesn't work, temporarily disable the software and troubleshoot. For corporate networks , modifications to the local hosts file or proxy rules may also be involved. You can check whether there are any abnormal entries in the C:\Windows\System32\drivers\etc\hosts file, delete the redundant content and save it.

　　Local DNS cache errors not only affect access speeds but can also pose security risks. For example, if the system cache contains forged resolution records tampered with by malware, users may be redirected to phishing pages when visiting websites. Therefore, regularly clearing the DNS cache is a good cybersecurity practice. Manually refreshing the cache periodically (e.g., monthly) is recommended, especially after changing network environments, modifying routers, or adjusting DNS servers. Prompt clearing can effectively prevent unexpected failures.

　　From an operations and maintenance perspective, understanding the DNS cache mechanism is equally important for website administrators and developers. Many people find that some users cannot access a new website or change servers. This is not due to website failures, but rather to outdated cache updates. In this case, you can notify users to clear the local DNS or temporarily shorten the TTL (Time to Live) of DNS records to allow new resolution records to take effect more quickly. This is particularly common during website migrations, CDN switches, or SSL certificate renewals.

　　In addition to manual command operations, tools can also be used for automated clearing. For example, in Windows, the "Network Diagnostics" feature can automatically detect and reset the DNS, while macOS users can use third-party network optimization software for one-click clearing. Technical personnel can also write a simple script to periodically execute the flushdns command to maintain up-to-date system resolution.

　　It's worth noting that clearing the DNS cache does not affect normal Internet access or delete browser history or cookies. It simply allows the system to retrieve the latest domain name resolution information, a safe and harmless process. Therefore, when encountering website access anomalies, slow web page loading, or incorrect domain name pointing, flushing the DNS cache is one of the first troubleshooting steps.

　　FAQs:

　　Q1: Will clearing the DNS cache affect network speed?

　　A1: No. Clearing the DNS cache simply removes old resolution records. After clearing, the system will requery the DNS server for the latest data. There may be a slight delay on the first access, but the cache will be re-cached, so overall speed will not be negatively impacted.

　　Q2: Why can't I access the website after clearing the cache?

　　A2: If you still can't access it after clearing the cache, it may be due to a problem with the DNS server itself, a network blockage, or the target website is down. You can try changing the DNS server or using the ping command to check if the IP address can be resolved.

　　Q3: Does the router also have a DNS cache?

　　A3: Some high-end routers do cache DNS records. If multiple devices can't access a website, try restarting the router or logging into the management interface to manually refresh the DNS.

　　Q4: Is it necessary to clear the DNS cache frequently?

　　A4: Generally, frequent clearing is not necessary. However, if you notice access anomalies, domain name resolution errors, or if a website changes servers, it is recommended to manually refresh it. For users who use the same network for a long time, clearing the cache monthly is a suitable frequency.

　　Q5. How do I clear the DNS cache on my phone?

　　A5: On Android, you can toggle private DNS on and off again in Settings → Network & Internet → Private DNS. iPhone users can reset the DNS cache in Settings → General → Transfer or Restore iPhone → Reset Network Settings. You can also force a refresh by switching to Airplane mode and then turning the network back on.

　　In summary, the local DNS cache is both a great helper for improving access speed and a common source of network access errors. When encountering problems like website inaccessibility, resolution anomalies, and redirect errors, clearing the DNS cache can often quickly restore normal operation. Understanding the cleaning methods for different operating systems, combined with DNS server optimization and security testing, will not only improve your online experience but also ensure a more stable and reliable network environment. Regularly clearing the DNS cache is fundamental to maintaining a healthy network and a safety habit every internet user should cultivate.