This is a DNS server with configurable latency to simulate slow or misconfigured DNS

Choose desired delay for your IP address:
and use as your DNS server.
why this web site is so slow?

How DNS resolution affects performance

Here are some examples

How different operating systems and browsers handle DNS

Windows 2000, XP, Vista, Windows 7, Windows 8, Linux, iOS, Android all behave differently

List of hosts with short DNS TTL

Examples of well known hosts which have low DNS TTL values (0-60 s) and other examples of funny DNS configurations

Why so many websites have very short DNS TTL value?

A recommended TTL value for and A record is usually between 30 and 60 minutes ([1], [2]). Short TTLs (30s - 5m) are used for Failover, Load Balancing or DDOS mitigation. There are some hosts with very short TTLs (20-30s) and even 0s (no caching at all!)!

Some caching DNS servers set their own minimal TTL values, override the original TTLs

In most cases overriding minimal TTL for Web site and setting it to 120-300s doesn't have any negative impact.

DNS best practices for web performance

Follow these easy steps to avoid performance degradation caused by slow DNS lookup

How to configure DNS for a company's proxy server

Conditional DNS resolution, DNS pre-resolving, monitoring and other best practices

List of DNS timeouts

List of DNS timeouts for your reference

How to hack Namebench? (2014 Guide)

The last release of Namebench, the DNS Benchmark, dated Jun 2010. Learn how to modify Namebench for your need to get correct resutls

Google public DNS ( and latency and reliability test


Special DNS zones for testing purposes

Reserved DNS names

.test .example .localhost .invalid wikipedia