# How DNS TTL Affects Website Migration

DNS TTL is a small number with a big impact during website migrations. TTL means time to live. It tells recursive resolvers how long they may cache a DNS answer before asking for a fresh one.

When you move a website to a new host, CDN, or load balancer, TTL helps explain why some visitors see the new site while others still reach the old one.

Why TTL matters

Your authoritative DNS provider may show a new record immediately after you save it. Most visitors do not query authoritative DNS directly. They use recursive resolvers from ISPs, public DNS providers, companies, browsers, or operating systems.

Those resolvers can keep using the old answer until the TTL expires.

That is why DNS migrations often feel inconsistent. The change is live at the source, but cached answers still exist in the network.

Use AccessTest DNS Lookup and URL Check to compare DNS answers and website behavior:

https://www.accesstest.net/tools/dns-lookup/

https://www.accesstest.net/tools/url-check/

A simple TTL example

Suppose your old record is:

```txt example.com A 192.0.2.10 TTL 86400 ```

A TTL of `86400` seconds means 24 hours. If a resolver cached that answer five minutes before your change, it may keep sending users to the old IP for almost a full day.

If you lower the TTL before the migration:

```txt example.com A 192.0.2.10 TTL 300 ```

Then most compliant resolvers should refresh within about five minutes after their cached answer expires.

Lower TTL before the cutover

For a planned migration, lower TTL in advance. Do it at least one previous TTL period before the final change.

For example, if the current TTL is 24 hours, lower it to 300 seconds at least 24 hours before the migration window. That gives existing caches time to expire and pick up the shorter TTL.

Then, when you change the destination, the new value can spread faster.

TTL does not fix every delay

TTL is important, but it is not the only cache involved. You may also see delays from:

- CDN cache. - Browser DNS cache. - Operating system cache. - Corporate DNS resolvers. - ISP resolver behavior. - Application or reverse proxy cache.

Some resolvers may also behave differently from the exact TTL you publish. Treat TTL as a planning tool, not a perfect global timer.

Safer migration plan

1. Audit current A, AAAA, CNAME, MX, TXT, and CDN records. 2. Lower website-related TTL values before the migration. 3. Prepare the new host or CDN with SSL certificates and redirects. 4. Test the new destination directly before changing public DNS. 5. Change DNS during a low-traffic window. 6. Keep the old origin available until the old TTL window has passed. 7. Verify from multiple regions and resolvers. 8. Raise TTL again after the migration is stable.

This gives you a clearer rollback path and reduces the chance of users landing on a half-migrated site.

Rollback planning

A rollback is also affected by TTL. If you switch to the new destination and then switch back, resolvers that cached the new answer may continue sending users there until TTL expires.

Before migration, make sure both old and new environments can serve a valid version of the site for a while. That overlap is often safer than expecting every resolver to update instantly.

What to check after changing DNS

After the cutover, verify:

- A and AAAA answers. - CNAME targets. - TTL values. - SSL certificate coverage. - HTTP status codes. - Redirect destinations. - Response time from key regions. - Whether `www` and the root domain behave consistently.

FAQ

What TTL should I use before migration?

Many teams use a short TTL such as 300 seconds for migration windows. The right value depends on your DNS provider, traffic, and operational needs.

Should TTL stay low forever?

Usually no. Low TTL can be useful during changes, but higher TTL can reduce repeated lookups and improve cache stability after the site is settled.

Why do some users still see the old site?

Their resolver, device, browser, or network may still have a cached answer. The old environment should stay available until the cache window has passed.

Does TTL affect SEO?

Indirectly. A messy migration can create downtime, wrong redirects, or inconsistent crawl behavior. A planned TTL strategy helps reduce those risks.