YAML or YML: What Is the Difference?

If you work with code, software, or computer files, you may see both YAML and YML. At first, these names can look like two different file types. This can make people ask: YAML or YML — which one is correct?

The good news is that the answer is simple. YAML and YML refer to the same data format. The main difference is the file extension used at the end of the file name.

For example, you may see:

• config.yaml
• config.yml

Both files can use the YAML format. The choice between .yaml and .yml often depends on the software, project, or coding style being used.

YAML is a simple format used to store data in a way that is easy for people to read. It is common in software settings, configuration files, automation tools, and development projects.

In this guide, you will learn what YAML means, why both .yaml and .yml exist, whether one is better, how to choose between them, and how to avoid common mistakes.

YAML or YML – Quick Answer

YAML and YML are the same data format.

The difference is only the file extension:

• .yaml = YAML file
• .yml = YAML file

For example:

config.yaml

and

config.yml

can both contain YAML data.

There is no different YAML language called “YML.” YML is simply a shorter file extension for YAML.

The most important rule is to follow the file name and extension expected by the tool or project you are using.

What Is YAML?

YAML is a human-readable data format.

The name originally stood for “Yet Another Markup Language.” Later, the name was changed to “YAML Ain’t Markup Language.”

YAML is made to be easy for people to read and write.

A simple YAML file can look like this:

name: John

age: 25

city: London

This example stores three pieces of data:

• Name: John
• Age: 25
• City: London

YAML uses spaces and simple symbols to show how data is organized.

You may see YAML in:

• Software settings
• App configuration
• Cloud tools
• Automation
• Development projects
• Data files
• CI/CD systems
• Docker and Kubernetes files

What Is YML?

YML is not a separate format.

It is a short form of the .yaml file extension.

For example:

settings.yml

is normally a YAML file.

You may also see:

settings.yaml

Both can contain YAML data.

The choice of .yml or .yaml does not normally change the data format inside the file.

YAML vs YML: The Main Difference

The main difference is the file extension.

Feature	YAML	YML
Meaning	YAML data format	Short file extension for YAML
Common extension	.yaml	.yml
Data format	YAML	YAML
Human-readable	Yes	Yes
Different language?	No	No
Can store YAML data?	Yes	Yes
Main difference	Longer extension	Shorter extension

So, when someone asks “Is YAML or YML correct?”, both can be correct when they refer to a YAML file.

Why Are There Two Extensions?

One reason is simple: file extensions have different length limits and traditions across older computer systems.

The .yml form became popular because some systems and projects preferred shorter file extensions.

The .yaml form is also widely used because it clearly matches the name YAML.

Today, you can find both forms in real software projects.

The important point is that .yml does not mean a different type of data.

YAML File Examples

Here are some common file names:

config.yaml

settings.yaml

database.yaml

docker-compose.yml

config.yml

settings.yml

The .yaml and .yml files can both contain YAML data.

For example, this:

name: Alice

language: English

can be stored in:

data.yaml

or:

data.yml

The extension alone does not change the YAML content.

Is YAML or YML Better?

There is no single rule that makes one extension correct for every project.

Instead, check the tool or project you are working with.

For example, if a project already uses:

config.yml

it may be best to keep using .yml for similar files.

If a project uses:

config.yaml

then .yaml may be the better choice for consistency.

A simple rule

Follow the convention of the project or tool.

This avoids confusion and keeps file names consistent.

YAML or YML in Programming

Developers use YAML for many types of configuration.

For example:

server:

  host: localhost

  port: 8080

This tells a program about a server host and port.

The same data could be saved as:

server.yaml

or:

server.yml

The contents are still YAML.

However, some tools may expect a specific file name. In those cases, you should use the exact name and extension required by the tool.

YAML or YML in GitHub

You may see YAML files in GitHub projects.

For example, GitHub Actions workflow files commonly use YAML files in:

.github/workflows/

You may see names such as:

build.yml

or:

deploy.yaml

The exact extension used depends on the project and the file’s purpose.

When working in an existing repository, check the files already used by the project and follow the same pattern.

YAML or YML in Docker

Docker-related files are another place where people may see .yml.

For example:

docker-compose.yml

This is a YAML file.

The file contains settings that describe services, networks, volumes, and other options.

The important part is not that .yml is a different format. It is still YAML.

Modern Docker Compose documentation also uses names such as compose.yaml, so the exact file name can depend on the tool and its current conventions.

YAML or YML in Kubernetes

Kubernetes configuration files also commonly use YAML.

For example:

deployment.yaml

may contain Kubernetes settings.

You may also find:

service.yml

in some projects.

Again, the data format is YAML.

The project or tool may have its own file naming rules, so always check the documentation when the exact name matters.

British English vs American English

There is no British English versus American English difference between YAML and YML.

These are technical terms and file extensions.

The spelling does not change based on the country.

You can use:

• YAML
• .yaml
• YML
• .yml

The key difference is the file extension, not English spelling.

Which One Should You Use?

If you are starting a new project, the best choice depends on the project and the tool you use.

For an existing project

Follow the style already used in the project.

If most files use:

.yaml

use .yaml.

If they use:

.yml

use .yml.

For a tool with a required name

Use the exact file name given in the tool’s documentation.

For example, if a tool expects:

config.yaml

do not rename it to:

config.yml

unless the tool says that both are supported.

For team projects

Consistency matters.

If your team has a file naming rule, follow it.

The main goal is to make files easy to find and understand.

Common Mistakes With YAML and YML

1. Thinking YML is a different language

Incorrect idea: YML is a separate language.

Correct: .yml is another common extension used for YAML files.

Example:

settings.yml

This can be a YAML file.

2. Changing the extension without checking the tool

Mistake:

required-config.yaml

is changed to:

required-config.yml

without checking whether the software accepts the new name.

Correct: Follow the tool’s file-name rules.

3. Mixing extensions without a reason

A project may contain both:

config.yaml

and:

settings.yml

This is not automatically wrong, but it can make a project less consistent.

4. Thinking .yaml means a newer format

The .yaml extension does not mean that the file contains a newer version of YAML.

Both extensions can represent YAML data.

5. Calling a YAML file “YML language”

Less clear:

“This is written in YML language.”

Better:

“This is a YAML file.”

YAML is the format name. .yml is a file extension.

YAML or YML: 10 Examples

1. config.yaml is a YAML file.
2. config.yml can also be a YAML file.
3. YAML files are often used for configuration.
4. The .yml extension is a common short form.
5. The .yaml extension clearly matches the name YAML.
6. Always check the tool’s required file name.
7. A .yml file can contain YAML data.
8. A .yaml file can contain YAML data.
9. Project rules may tell you which extension to use.
10. YAML and YML do not represent two different data formats.

Real-Life Usage

In software projects

A developer may create:

config.yaml

to store application settings.

In GitHub projects

A project may use:

build.yml

for an automation workflow.

In Docker projects

You may see:

compose.yaml

or other YAML-based configuration files.

In Kubernetes

A project may contain:

deployment.yaml

for Kubernetes configuration.

In team documentation

A developer may say:

“Please update the YAML file.”

This normally refers to a file using either .yaml or .yml.

Related Search Questions

Is YAML the same as YML?

Yes. YAML is the data format, while .yml is a common file extension used for YAML files.

Is .yml or .yaml correct?

Both extensions can be used for YAML files. The right choice depends on the project or tool you are using.

Is YML short for YAML?

Yes. .yml is a shorter file extension commonly used for YAML files.

Can I rename .yml to .yaml?

Often, yes, because both can represent YAML files. However, check the software or project rules first. Some tools expect a specific file name.

Can a YAML file have a .yml extension?

Yes. A YAML file can use .yml as its extension.

YAML or YML: Usage and Search Trends

People often search for “yaml or yml” when they start working with configuration files or see both extensions in software projects.

Common search questions include:

• YAML or YML?
• Is .yml the same as .yaml?
• Which YAML extension should I use?
• Is .yaml better than .yml?
• Can I rename .yml to .yaml?
• What does .yml mean?
• What is a YAML file?

Exact search volume and Google Trends numbers should not be added without reliable current data. Search interest can also change by tool, programming language, and project type.

The key usage point is simple: both .yaml and .yml are used for YAML files.

Comparison Table

Term	Meaning	Usage	Example
YAML	Name of the data format	Configuration and data	YAML file
.yaml	Full file extension	YAML files	config.yaml
YML	Common short form	Informal name for .yml files	YML file
.yml	Short file extension	YAML files	config.yml

FAQs

1. Which is better, YAML or YML?

YAML is the name of the format. .yaml and .yml are both file extensions used for YAML files. For a project, the best choice is usually the extension required by the tool or the one already used by the team.

2. Is .yml outdated?

No. .yml is still used in many software projects. It is not simply an old or invalid form of YAML. The exact extension used depends on the project and tool.

3. Is .yaml more correct than .yml?

Neither extension makes the YAML data itself different. .yaml is the full extension, while .yml is a shorter common extension. Always follow the rules of the software or project you are using.

4. Can YAML use both .yaml and .yml?

Yes. YAML data can be stored in files ending in either .yaml or .yml. However, a specific program may look for one exact file name, so the tool’s rules still matter.

5. What does YML stand for?

YML is commonly used as a short name for the .yml file extension. The actual format is called YAML. It is not a separate data language from YAML.

6. Why do people use .yml instead of .yaml?

The .yml extension is shorter and has been used by many software projects for years. Some tools and projects also use it as their standard file extension. In other projects, .yaml is preferred.

7. Should I use YAML or YML in a new project?

Check the tool and the project’s style first. If there is no rule, choose one extension and use it consistently. This makes your project easier to read and manage.

Conclusion

The difference between YAML or YML is much simpler than it may first seem. YAML is the name of the data format, while .yaml and .yml are file extensions used for YAML files.

For example, both of these can be YAML files:

config.yaml

and:

config.yml

The extension does not create a new data format. Instead, the choice often comes from a project’s style, a software tool, or a required file name.

If you work on an existing project, look at the other configuration files and follow the same pattern. If a tool’s documentation gives you a required file name, use that exact name.

For a new project, consistency is more important than trying to treat one extension as a completely different format.

The easiest way to remember the difference is:

YAML = the data format

.yaml = full file extension

.yml = short file extension

So, when you see YAML vs YML, remember that they normally point to the same YAML format.

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