A Fully Qualified Domain Name Can Contain How Many Characters ?

If you’re asking “A fully qualified domain name can contain how many characters?”, you’re probably dealing with DNS, networking, web hosting, or exam preparation. This question is common because the rules sound confusing—and many online answers oversimplify them.

Let’s clear it up properly, in simple English, with real-world context and no unnecessary jargon.

The Short, Correct Answer

A Fully Qualified Domain Name (FQDN) can contain up to 255 characters in total, including dots (.).

However, there are important details and limits inside that number, which is where most confusion comes from.

What Is a Fully Qualified Domain Name (FQDN)?

A Fully Qualified Domain Name is the complete, absolute domain name that specifies a host’s exact location in the DNS hierarchy.

Example of an FQDN

Hostname (www)
Second-level domain (example)
Top-level domain (com)
Dots separating each level

The Official Character Limit for an FQDN

Total length limit

Maximum: 255 characters
This count includes all dots

This limit comes from DNS standards that define how domain names are stored and transmitted.

Why You’ll Also See “253 Characters” Mentioned

You may see answers saying 253 characters instead of 255. Both can be correct, depending on context.

Here’s why:

The DNS system allows 255 characters total
A fully written FQDN often ends with a trailing dot, like:
When written without the trailing dot, the usable visible length becomes 253 characters

In simple terms:

255 characters → technical DNS maximum
253 characters → practical, written domain name limit

Most exams and documentation accept 255 characters as the correct answer.

Label Limits Inside a Fully Qualified Domain Name

An FQDN is made of labels (the parts between dots).

Label rules:

Each label can be up to 63 characters
Labels are separated by dots
You can have multiple labels, as long as the total length stays within the limit

Example

Each word between dots is a label.

Character Rules for Domain Names

A fully qualified domain name can contain:

Letters (a–z)
Numbers (0–9)
Hyphens (-)

Restrictions:

No spaces
No special symbols
Labels cannot start or end with a hyphen
Dots only separate labels

These rules help ensure compatibility across the internet.

Visual Breakdown of the Limits

Rule	Limit
Total FQDN length	255 characters
Practical written length	253 characters
Maximum per label	63 characters
Allowed characters	Letters, numbers, hyphens

Why These Limits Exist

The limits exist because:

DNS records must fit into fixed-size structures
Domain names need to be transmitted efficiently
Compatibility across networks is critical

Without limits, DNS lookups would be slower and less reliable.

Real-World Examples

Valid long FQDN

Invalid FQDN (too long)

Exceeds total character limit
Or contains a label longer than 63 characters

Most domain registrars and DNS servers will reject invalid names automatically.

Common Mistakes People Make

1. Thinking Each Part Can Be 255 Characters

No—the entire name combined must fit within the limit.

2. Forgetting the Dots Count as Characters

Every dot matters in the total length.

3. Ignoring Label Limits

Even if the total length is under 255, a single label longer than 63 characters is invalid.

How This Applies in Real Life

Understanding FQDN limits is important when:

Designing enterprise networks
Creating deep subdomain structures
Configuring servers and certificates
Working with cloud platforms
Preparing for IT or networking exams

Long, poorly planned domain names can break systems in unexpected ways.

Exam-Ready Answer (Short Form)