DNS TTL Checker Tool
TTL Checker (Time To Live) is used to determine how long a DNS record remains valid in a resolver's cache. It helps verify when updates will be visible across the internet.
Know exactly when your DNS changes will take effect. Monitor Time-To-Live (TTL) values and estimate cache refresh timing instantly.
Type a domain to check DNS records.
What is DNS TTL (Time to Live)?
TTL (Time to Live) is a critical numerical value in every DNS record that determines how long a resolver should cache a DNS response before requesting a fresh update from the authoritative server. Expressed in seconds, TTL acts as the "expiration date" for the data in the DNS cache.
Understanding TTL is essential for anyone managing a domain. It balances the trade-off between website performance (longer TTLs reduce server load and speed up lookups) and update flexibility (shorter TTLs allow for rapid changes during server migrations or outages).
How TTL Controls the Web
Cache Countdown
When a DNS server (like Google Public DNS) first fetches your record, it starts a countdown from your set TTL. If your TTL is 3600 (1 hour), the resolver will serve that cached answer to every user for the next 60 minutes without asking your server again.
TTL Drift
This is why different users see different TTL values. One user might query the resolver 10 minutes into the cycle (seeing 3000s remaining), while another queries 55 minutes in (seeing only 300s). Our TTL Checker helps you visualize this current "remaining" time.
Strategic TTL Management
Choosing the right TTL is a balancing act. High TTLs (e.g., 86400s / 1 day) are excellent for stable sites because they maximize speed and reliability. If your authoritative DNS server goes down temporarily, users can still access your site as long as the record remains in their local ISP's cache.
However, high TTLs are dangerous during migrations. If you switch servers with a 24-hour TTL, you have no way to "cancel" the old cached data. Conversely, Low TTLs (e.g., 60s - 300s) offer extreme agility, often used for failover systems or during active development where immediate updates are required.
TTL Best Practices for Migrations
| Stage | Recommended TTL | Reason |
|---|---|---|
| Steady State | 3600 - 86400s | Maximizes stability and speed. |
| Pre-Migration | 300s | Lower this 24h before the actual switch. |
| Active Switch | 60s | Allows for instant rollbacks if issues arise. |
| Post-Migration | 3600s+ | Raise back up once stability is confirmed. |
TTL Frequently Asked Questions
Why does my TTL look different on every check?
Because you are seeing a "snapshot" of the resolver's cache. If you query a resolver 5 minutes after it refreshed, it will show your TTL minus 300 seconds. Track the full update cycle with our Global Propagation Checker.
Can I set a TTL to 0?
While technically possible in some systems, setting a TTL of 0 is generally discouraged. It can cause a massive spike in traffic to your nameservers and some older resolvers may default a 0 TTL to a much larger value (clamping) to protect themselves.
What is negative TTL caching?
If a domain doesn't exist (NXDOMAIN), resolvers cache that failure too. This is controlled by the "Minimum TTL" value in your SOA record. It prevents bots from hammering your servers for domains that aren't there.
Master Your Cache Timing
Don't let slow propagation surprise you. Use this tool during migrations, DNS troubleshooting, or security audits to ensure your records are behaving as expected and that your cache strategy aligns with your business needs.