Convert DNS TTL (Time To Live) values between seconds and human-readable format. Understand how TTL affects DNS caching, propagation speed, and record management. All calculations run locally in your browser.
TTL (Time To Live) is a value in DNS records that tells resolvers how long to cache a record before requesting a fresh copy from the authoritative server. Measured in seconds, TTL directly controls the tradeoff between DNS query performance and how quickly changes propagate across the internet.
When you query a domain using our DNS Lookup tool, every record returned includes a TTL value. Understanding TTL is essential for anyone managing DNS records, whether you're setting up email authentication with MX records or configuring dynamic DNS.
Different types of DNS records typically use different TTL values based on how frequently they change:
| TTL (Seconds) | Human-Readable | Typical Use |
|---|---|---|
| 60 | 1 minute | Active failover, load balancers, CDN edge records |
| 300 | 5 minutes | Dynamic DNS (DDNS), frequently updated records |
| 900 | 15 minutes | Pre-migration (lowered before a DNS change) |
| 1800 | 30 minutes | Active management, regular updates |
| 3600 | 1 hour | Standard default for most providers |
| 14400 | 4 hours | Stable records with occasional changes |
| 43200 | 12 hours | Relatively stable infrastructure records |
| 86400 | 1 day | Stable records (NS, SOA) |
| 604800 | 7 days | Very stable records that almost never change |
Pro Tip: Before making any DNS change, lower your TTL to 300 seconds (5 minutes) at least 24-48 hours in advance. This ensures that when you make the change, all caching resolvers will pick up the new record within 5 minutes instead of waiting for the old high TTL to expire. After the change is stable, raise the TTL back. This technique is especially important when migrating MX records or changing your website's IP address.
DNS propagation is the time it takes for DNS changes to reach all resolvers worldwide. TTL is the primary factor controlling propagation speed:
| Scenario | Old TTL | Propagation Time | Strategy |
|---|---|---|---|
| Emergency DNS change | 86400 (1 day) | Up to 24 hours | Lower TTL in advance next time |
| Planned migration | 300 (5 min, lowered) | 5-10 minutes | Pre-lowered TTL, smooth transition |
| CDN/failover switch | 60 (1 min) | 1-2 minutes | Always-low TTL for dynamic routing |
| New domain setup | 3600 (1 hour) | Up to 1 hour | Standard default, acceptable for new records |
Note that propagation time is bounded by the old TTL value, not the new one. If your current record has a 24-hour TTL, resolvers that cached it just before the change will hold the old value for up to 24 hours, regardless of the new TTL you set.
Different DNS record types benefit from different TTL strategies based on how frequently they typically change:
TTL creates a fundamental tradeoff between freshness and performance:
For home networks, the DNS resolver you use also matters. Run our DNS Speed Benchmark to find the fastest resolver for your location, and learn about the differences between ISP DNS and custom DNS.
Follow this checklist when planning any DNS change to minimize downtime:
# 48 hours before migration:
1. Check current TTL values (dig domain.com A)
2. Lower TTL to 300 seconds on records you'll change
3. Wait for old TTL to expire (up to current TTL)
# At migration time:
4. Make the DNS change (new IP, new mail server, etc.)
5. Verify new records propagate (use DNS lookup tools)
6. Monitor for 24 hours
# After migration is stable:
7. Raise TTL back to normal (3600-86400)
8. Remove old infrastructure after 2x old TTLFor most DNS records, 3600 seconds (1 hour) is a good default. Use lower values (300 seconds) for records that change frequently or during migrations. Use higher values (86400 seconds) for stable records like NS or TXT authentication records.
Technically, TTL 0 instructs resolvers not to cache the record at all. However, some resolvers may still cache briefly (30 seconds to a few minutes) for performance reasons. A TTL of 0 is rarely practical because it creates significant load on authoritative servers.
Changes take effect after the old TTL expires from all caches. If the current TTL is 3600 (1 hour), resolvers that cached the old record just before the change will update within 1 hour. Global propagation may take longer if some resolvers override TTL values.
Yes. Each DNS record can have its own TTL value. It's common to use a lower TTL for A records (which may change during infrastructure changes) and higher TTL for MX or TXT records (which change infrequently).
Very low TTL values (under 60 seconds) increase the number of DNS queries hitting your authoritative servers, which can increase load and costs. They also make your site more dependent on DNS server availability — if your DNS goes down, cached records expire quickly and your site becomes unreachable faster.
High TTL values (over 86400 seconds) mean DNS changes take a long time to propagate. If you need to make an emergency change (like moving to a new server after an outage), users with cached records won't see the change for hours or days. Always lower TTL before planned changes.
TTL does not directly affect SEO. However, during a migration with high TTL, some users (and search engine crawlers) may be directed to the old server for an extended period. This can cause temporary 404 errors or stale content, which could indirectly impact search rankings if the migration takes too long.
About Tommy N.
Tommy is the founder of RouterHax and a network engineer with 10+ years of experience in home and enterprise networking. He specializes in router configuration, WiFi optimization, and network security. When not writing guides, he's testing the latest mesh WiFi systems and helping readers troubleshoot their home networks.
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