What Is TTL? The Basics of Time to Live

No, “TTL” isn’t a misspelled abbreviation for “talk to you later” — it stands for “Time to Live.” It sounds pretty official, right? I can picture Tom Cruise using the phrase in his next Mission Impossible movie! Now, let’s get to the point.

The TTL value determines how long that IP address is valid in your recursive DNS resolver’s cache.

When you type a domain name like http://www.hostingadvice.com into your browser, the recursive DNS resolver (such as Cloudflare’s 1.1.1.1 service) sends the DNS query to the authoritative DNS server.

The server then sends the DNS record associated with the website’s IP address back to the resolver, which caches it. Finally, the resolver sends the IP address to your browser along with the TTL value.

So, if you or any other device on the network requests the same website again, the cached IP address will be used instead of another domain lookup. Once the TTL expires, you’ll have to perform another lookup to get the current IP address of the domain. By “current,” I mean it might have changed.

I had a great time writing this piece, and I know you’re going to enjoy reading it. It’s time to talk about TTL!

You can compare TTL in the Domain Name System (DNS) to the due date for the latest bestseller in the library. When you check out a book, you can read it as many times as you like during the checkout period (I’ve never read the same book more than twice) — but you have to return it before the due date. If you want to keep it longer, you’ll need to check it out again.

Unlike a library book checkout period (which is typically measured in days), TTL is measured in seconds. During this, recursive DNS resolvers are instructed to cache a DNS query response before checking for updates.

How Does TTL Work?

For example, let’s say the TTL on the IP address-related DNS record for http://www.HostingAdvice.com is set to 3600 seconds (one hour). This means the authoritative DNS server (the server that stores and manages the website’s DNS records) instructs the recursive DNS resolver (the middleman that retrieves these records) to cache the website’s IP address for this one-hour period.

You can access the website as many times as you want to during this period without your device needing to perform a new DNS lookup.

As you can imagine, caching the IP address saves a lot of time and reduces the load on the DNS server. Simply put, TTL plays a key role in making your internet experience faster and more efficient.

In this section, I’ll present a high-level view of how DNS and TTL work together. They’re like two peas in a pod. Or, if you prefer, DNS is like Batman and TTL is like Robin.

I’ll start with the role of DNS on the internet.

The Role of DNS on the Internet

We interact with the internet through domain names, while internet-connected devices communicate with each other through IP addresses.

The Domain Name System is like a phonebook for the internet — it converts human-readable domain names (like http://www.HostingAdvice.com) into IP addresses (like 192.168.1.1) that your web browser can use to connect to the web server hosting the HostingAdvice website.

DNS also supports a variety of record types, which I will dive into later.

How TTL Influences DNS Queries

When you access a website from the comfort of your home, your router forwards the DNS query to a recursive DNS resolver. The DNS resolver then queries the authoritative DNS server and caches the DNS records, which the server sends back to it. This includes the website’s IP address.

The IP address records are called Address Records (A Records) for IPv4 addresses and IPv6 Address Records (AAAA Records) for IPv6 addresses.

You don’t need to know all the types of DNS records (yet), but one in particular is quite interesting: Canonical Name Records (CNAME Records), AKA alias domain names. This means it doesn’t matter whether you enter HostingAdvice.com or www.HostingAdvice.com in your browser — both will lead you to the same website.

Now, the TTL value dictates how long these cached records are valid before the DNS resolver must refresh them from the authoritative DNS server.

Note: A router is a type of DNS resolver, but it doesn’t “resolve” DNS queries on its own — it simply forwards them to recursive DNS resolvers.

DNS Caching

You already know recursive DNS resolvers cache DNS records based on TTL, reducing the need for repeated lookups. I bet you didn’t know your browser caches DNS records too!

The issue is, if you switch off your device, those records will be erased from its cache. Well, this isn’t exactly a “problem,” because the records will still exist in the recursive DNS resolver’s cache, provided they haven’t timed out.

The Process

Now that your basics are crystal clear, I’m going to summarize the domain record retrieval process and highlight how TTL plays an instrumental role in speeding things up (one look at Step 3 is enough to understand this).

• Step 1: You enter a website URL in your browser.
• Step 2: The recursive DNS resolver checks if the DNS record is cached.
• Step 3: If the record is cached and within the TTL, it returns the cached data. If not, it queries the authoritative DNS server.
• Step 4: Repeat.

If you love numbers, you’re in for a treat. It’s time to better understand TTL values!

TTL is measured in seconds and is set by the entity managing the DNS records for your domain — typically your DNS provider (like Cloudflare, Google DNS, or AWS Route 53) or web hosting provider (like GoDaddy, Bluehost, or SiteGround).

They assign a default value, such as 3600 seconds (one hour) or 86400 seconds (one day), for each DNS record, which you, as the domain’s owner or administrator, can adjust as needed.

Typical TTL Values

Continuing from where we left off, your DNS provider or web host may set a default TTL of one hour for some records and one day for others.

These values indicate how stable or frequent changes are expected for each record. Since you know your website better than anyone, consider these values when configuring TTL for your DNS records:

• Low TTL: 300 seconds (5 minutes) — used for records that change frequently or during transitions like DNS updates.
• Medium TTL: 3600 seconds (1 hour) — a common default setting, balancing performance and flexibility.
• High TTL: 86400 seconds (24 hours) — used for more static records that rarely change, optimizing caching.

I’ll explain the types of DNS records and how to configure TTL settings for them soon.

Short vs. Long TTLs

There’s a significant difference between a TTL of five minutes and one day. In fact, a TTL of one day means a DNS record is cached in the recursive DNS resolver’s cache for approximately 17,000 times longer than a record with a TTL of five minutes!

For a betting understanding of the advantages and disadvantages of short and long TTLs, read on.

Short TTL (e.g., 300 seconds):

• Advantages:
  • Faster DNS updates.
  • Helpful during DNS migrations or when changing IP addresses.
• Disadvantages:
  • Increased load on authoritative DNS servers.
  • Slightly slower performance for users.

Long TTL (e.g., 86400 seconds):

• Advantages:
  • Better performance due to long-term caching.
  • Reduced DNS query load.
• Disadvantages:
  • Slow propagation of DNS changes.
  • Harder to respond quickly to updates or emergencies.

I suggest adjusting your TTL settings when needed. For instance, if you’re migrating your website to a new server or IP address, you may want to set the TTL of your A record or AAA record to five minutes.

This way, the browsers of your users will refresh the record more quickly. When the migration is complete, you can increase the TTL to one hour.

I’ve already introduced three types of DNS records: A records, AAAA records, and CNAME records.

There are three more types of DNS records you should know about — Mail Exchange records (MX records), Name Server records (NS records), and TXT records. As promised, I’ll also cover the TTL settings you can configure for each.

A Record (Address Record)

There’s not much to add here, but for the sake of revision: An A record maps a domain name to an IPv4 address, while a AAAA record maps a domain to an IPv6 address.

Now, this might interest you: if your website has a static IP address (which is the norm), I recommend configuring a long TTL for it. Short TTLs, on the other hand, are used for dynamic services.

For example, if you run an online store that scales automatically during peak shopping hours, low TTLs ensure user requests always go to the right backend server.

CNAME Record (Canonical Name Record)

I’m not trying to reinvent the wheel here: CNAME records map one domain name to another domain — think of the www.HostingAdvice.com and HostingAdvice.com example. That’s just the basic use of a CNAME record.

For CNAME records, a medium TTL (like 3600 seconds) is typically used, as the target domain or infrastructure may change over time. For example, you could use a CNAME record to point to a cloud service or direct traffic to a load balancer.

MX Record (Mail Exchange Record)

Let’s say you own a domain called https://themushroomshop.com and use an email provider like Google Workspace to handle emails for all of your employees (for example, surajdeep@themushroomshop.com). You would need to create an MX record to direct all incoming emails for your domain to Google’s mail servers.

In other words, MX Records specify the mail server (or servers) responsible for receiving emails for your domain. As you may have guessed, this record is typically set with a medium or long TTL, since changes to email servers are infrequent.

NS Record (Name Server Record)

For starters, here’s something you might not know: authoritative DNS servers are also called nameservers. Have you ever been to a club? If you have, you may have seen a few bouncers at the entrance.

You can think of NS Records as the bouncers of the DNS world — they ensure your users are directed to the right nameservers that hold your domain’s DNS details. These records are typically associated with a high TTL to ensure stability, as nameservers usually don’t change very often.

Note: The NS Record plays a critical role in the initial stages of domain lookup. Why? The recursive DNS resolver starts by looking up the NS records for a domain to find its authoritative DNS server. Once it finds the nameserver, the resolver can extract other details, like the A or AAAA record for the domain.

TXT Record

A TXT Record is like a Swiss Army knife of DNS Records — it can be used for a variety of purposes. For example, if you want to set up email accounts for your employees using Google Workspace, the service provider will ask you to add a TXT Record to prove you own https://themushroomshop.com.

TXT Records are also used to secure your email — email security protocols like SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) are often configured using TXT Records. Due to their versatility, TXT Records often have a lower TTL for flexibility.

When you update your DNS records, it takes time for these changes to reflect across the internet. For example, if you update your website’s IP address, the change is made on the “official” nameservers for your domain (each website typically has at least a primary and secondary nameserver).

While these nameservers always have the most up-to-date records, recursive DNS resolvers worldwide may have a previously cached version.

DNS Propagation Explained

If you set the TTL to be too high for the A or AAAA Record, for instance, it may take longer for changes to propagate across all recursive DNS resolvers worldwide. The cached DNS record will only be updated once the TTL expires and the cache refreshes.

That’s why it’s a good idea to adjust TTL values when an update is around the corner — shorter TTLs speed up propagation.

Propagation Delays

Changes to DNS records (such as changing hosting providers or updating an IP address) can take longer to be recognized globally if the TTL is set too high. That’s why I recommend lowering the TTL before making any changes.

For instance, if you update the IP address of your website from A.1.2.3 to B.4.5.6, and you change the TTL to 5 minutes, anyone who accesses the website after the TTL changes to 5 minutes will see the new IP address B.4.5.6 within just 5 minutes.

Unfortunately, if you’ve already cached the old record, you’ll have to wait till it expires.

Best Practices for Managing DNS Propagation

When making significant changes to DNS records, it’s a good idea to lower the TTL for all relevant records.

For example, if you’re changing the IP address of your website, the primary DNS records you need to focus on are the A record or the AAAA record. Lower their TTL to about five minutes.

You don’t need to adjust the TTL values for records that are unaffected by the change. Once the DNS change has fully propagated and everything is working as expected, restore the TTL to a higher value (such as one hour) to reduce the DNS load and improve caching efficiency.

I bet you could list a few reasons why TTL matters in the grand scheme of things. After all, given how people on YouTube can turn just about anything I’d consider useless into something “useful,” it’s clear everything matters (I’m looking at you, 5 Minute Crafts).

But for now, let’s focus on TTL.

Here’s why it’s vital for website performance and security:

• Performance Optimization: While I understand your hesitation to set longer TTL values for your DNS records, they reduce the number of DNS lookups, speeding up response times for your users.
• Reduced DNS Server Load: The higher the TTL value, the fewer DNS queries are made. This, in turn, decreases the load on both the recursive DNS resolver and the authoritative DNS server, making the entire DNS resolution process more efficient.
• Balancing Flexibility and Performance:
  • You need to strike the right balance between flexibility and performance. Shorter TTLs allow for quick DNS changes and faster updates, but if you set them too short, it can slow down the browsing experience for your users.
  • On the other hand, longer TTLs enhance performance but can make it harder for you to implement rapid changes when necessary.
• Security Considerations:
  • Mitigating DNS Spoofing Risks: DNS spoofing is a type of cyberattack in which a malicious actor alters DNS records in a resolver’s cache. If you’re unfortunately targeted by a DNS spoofing attack, consider temporarily shortening your TTL values and implementing DNS Security Extensions (DNSSE). It’s also crucial to stick to trusted recursive DNS resolvers to enhance security.
  • DNS Failover Strategies: In environments requiring high availability, such as an eCommerce store (welcome back, https://themushroomshop.com), even a small amount of downtime can be disastrous for you in both the short and long term. DNS failover strategies with short TTLs are essential for quickly rerouting traffic in case of server failure, ensuring your site remains accessible to customers.

From performance optimization to reducing load on DNS resolvers and enhancing security, TTL may seem like just a number — but its value is immeasurable. How’s that for a poetic touch?

Choosing the right TTL configuration for your DNS records is not rocket science. Before tweaking the default TTL settings provided by your DNS provider or web host, take a moment to write down the six different types of DNS records (five, really, depending on your IP address format) on a piece of paper (or in a new Google Doc).

Besides each record type, note the appropriate TTL setting after reviewing the following considerations in detail.

Assessing Your Needs

You don’t need a short TTL for a website with content that doesn’t change very often. For example, Apple’s corporate website is updated occasionally (for instance, weekly), so there’s no need for recursive DNS resolvers to check for updates constantly.

Dynamic websites, on the other hand, like eCommerce or news websites, benefit from shorter TTLs. After all, you want your users to always have the most current data when they access your website.

Factors to Consider and Best Practices

This is where you start making serious notes. Here are some other factors you should consider:

• Frequency of DNS Changes: If you expect frequent updates (for instance, changing hosting providers or IP addresses), a lower TTL is advisable. I recommend using a low TTL (300-600 seconds) during critical DNS changes, like migrations, and reverting to a longer TTL (3600 seconds or more) once the changes are complete.
• Server Stability: If your server infrastructure is highly stable — your DNS records rarely change and your servers experience minimal downtime — using higher TTLs can improve performance.
• Website Traffic and Load: If you anticipate high traffic for your website, you may prefer longer TTLs to reduce the number of DNS queries and enhance performance.

Remember to regularly review and adjust TTL settings based on your performance needs and planned updates.

I’ve already mentioned you should modify the TTL for your DNS records as needed, but how exactly do you do that? If you’re on a web hosting plan, chances are you have a powerful control panel like cPanel or Plesk to manage all things related to your website.

As long as your hosting account has DNS management privileges (and in most cases, it does), you should be able to add, edit, or delete DNS records without a problem.

If your domain’s DNS is hosted by a third-party DNS provider or domain registrar (I recommend registering your domain through your web host to avoid complications), you’ll need to log in to that provider’s control panel to make any changes to your DNS settings.

Checking TTL

If you enjoy coding, you can also check DNS records using command line tools such as “nslookup,” (compatible with Windows, Linux, and macOS operating systems), “dig,” and “host.”.

To modify DNS records, you can use “nsupdate,” but note you’ll need direct access to the DNS infrastructure.

If you have a dedicated server or virtual private server (VPS) hosting plan, you can modify TTL directly from the command line. But don’t even think about it if you’re on a shared hosting plan!

Modifying TTL in a DNS Management Console:

Assuming your web host is “generous” enough to allow you to access and modify your DNS configuration through a control panel like cPanel, here’s a step-by-step guide for updating TTL values:

1. Log in to your cPanel account.
2. In the “Domains” section, look for the “Zone Editor” option.
3. Click on the “Zone Editor” and select the domain you want to edit.
4. You can now add, edit, or delete DNS records for your domain.

Save your changes and verify whether they’ve propagated across the internet.

Verifying TTL Changes:

It may take anywhere from a few minutes to 24 hours (or more in some cases) for DNS changes to propagate.

Rather than sitting around and waiting, it’s better to verify if your changes were successful. I recommend using DNS tools like “nslookup” (“nslookup yourdomain.com”) or “dig” (“dig yourdomain.com”).

Alternatively, you can use online tools like DNSstuff or MXtoolbox to check the status of your DNS records.

Are you a fan of the Ghostbusters franchise? You might believe the eccentric scientists chasing mythological and supernatural elements are just farming views.

While I’m not entirely against this “view” — and I’ve never seen or felt the presence of a ghost — I’m pretty sure they exist.

But I’m not here to debate the authenticity of ghosts or justify their existence. Instead, I’ll focus on busting some common TTL myths of my own.

Myth: TTL Changes Take Effect Immediately

As a best practice, if you want to tweak your DNS records, you should lower your TTL settings so they reflect on your users’ devices sooner. The word here is “sooner” — don’t expect the changes to take effect immediately.

Even when you lower the TTL, it takes time for existing caches to expire, so the change may not be immediate. Don’t forget to restore the original TTL once you’re done!

Myth: Lower TTL Is Always Better

Lower TTLs aren’t always better. For example, if you run a static website with minimal DNS changes on a day-to-day basis, it doesn’t make sense to set a low TTL for your DNS records.

A low TTL leads to more frequent DNS lookups, which can increase the load on your DNS servers and cause performance degradation for your users. In such cases, TTL values of 3600 seconds (1 hour) or more are typically preferred.

Dynamic websites, on the other hand, often interact with backend services like databases and APIs and can require more frequent DNS changes. Lower TTLs are better for such websites.

Myth: Higher TTL Guarantees Performance

While high TTL values can improve performance, they may also cause delays when DNS changes are required. You need to know when to use which TTL setting.

In summary, lower your TTL when you want to alter your DNS records and set higher values once the changes have propagated. Also, consider the nature of your website — whether it’s static or dynamic — when determining how high to set these values.

You’re a TTL genius at this stage. You not only know the ins and outs of TTL but also DNS. It’s important for you to set smart TTL settings to boost your website’s performance.

I mean, every second counts these days, and I’d hate for potential customers to ignore the brilliance of your website (I have faith in you) just because you don’t know how to play around with your TTL configuration.

Here are a couple more tips: monitor TTL’s impact on performance to find the optimal balance between speed and DNS load and consider traffic patterns when configuring your DNS settings. For example, during peak traffic hours, lower your TTL temporarily.

It’s time for you to get started!