Partial DNS failure can involve a resolver, VPN/filter, IPv6 path, stale cache or the site itself. Compare hostname lookup with direct access and another resolver/network. Test the same site on a mobile connection and on another device on the same Wi-Fi.
Differential
Likely causes of “Some websites fail with DNS errors while others work”, and how to tell them apart
- 1
The DNS resolver in use is failing for those names
What separates it Some sites fail with a DNS error while others load, and the same site works on another network.
How to confirm Test the same site on a mobile connection and on another device on the same Wi-Fi.
- 2
A VPN, content filter or security tool is blocking the domain
What separates it The site fails only with the filter or VPN on, and works when it is off.
How to confirm Turn the filter or VPN off for one test and reload the site.
- 3
A stale DNS cache on the device or router
What separates it A site that moved or changed address fails until the cache clears, and it works after a restart.
How to confirm Restart the browser and the device and flush the DNS cache as the system describes.
- 4
The site itself or its DNS is down
What separates it The same site fails everywhere, including on other networks and other devices.
How to confirm Check the site's status with a third-party checker or on another network.
Before you touch a setting
Record this first — changing settings destroys the evidence
- The exact browser error and the domain that fails.
- Whether the same domain fails on another device and on a mobile connection.
- Which DNS server the device and router are using.
Try in this order
0 of 4 completedCapture the exact symptom
ReversibleRecord the exact browser error and test the same domain on another device and cellular network.
Run the smallest isolation test
ReversibleDisable VPN/content filters for one test, restart the client and query the router/provider and a reputable alternate resolver.
Correct only the proven cause
ReversibleCorrect the failed filter/resolver or update router firmware; avoid permanent changes based on one unavailable site.
Verify before changing anything else
ReversibleLoad several previously failing domains after cache expiry and restart.
Stop boundary
When this stops being a self-service repair
- !Avoid permanent DNS changes based on one unavailable site; the fault may be the site's own.
Evidence ledger
Sources behind this answer
Exact questions
Common questions
Should I switch to a public DNS server?+
It is a fair test to see whether your provider's resolver is at fault, but change it for the test and check the result before making it permanent.
Why do only some sites fail with DNS errors?+
The DNS server may be slow or block particular names, or the site itself may be down.
How can I test?+
See if the site loads on another network.