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You may begin to notice that NPM
packages are often referred to by

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a combination of the name of the package
followed by a version number.

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An individual package can
have hundreds of versions and

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between these versions there
may be small or large changes.

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Some versions may be fixes of
bugs from previous versions.

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Some newer versions would break projects
that rely on previous versions.

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We can gather all of this
information from the version number.

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[SOUND] Package version numbers, consist
of three numbers, separated by periods.

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This style of numbering is called
semantic versioning or SemVer for short.

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NPM relies on semantic versioning to
communicate differences in updates,

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determine which packages to install,
and more.

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The first number is
the major version number.

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This changes for example, when a project
goes from version one to version two,

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it means there are breaking changes.

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Breaking changes mean that an app
using v1 might break when the package

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is updated to v2.

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The second number is for
minor or patch changes.

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From version 1.1 to 1.2,
there may be small changes that

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shouldn't affect apps
relying on previous versions.

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Finally, the last number
represents bug fixes.

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These are normally small fixes of
bugs from previous versions that

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shouldn't have any other effects.

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Along with version numbers,
semantic versioning uses symbols to

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indicate ranges of acceptable
versions of a package.

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We'll learn more about installing
packages in the next video.

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But let's first turn our attention to
these symbols and how we use them.

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The caret symbol is used to refer to all
greater versions in the same major range.

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With the caret, there can be minor
differences in versions, but

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nothing should break.

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The tilde refers to all versions greater

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than a given version in
the same minor range.

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This means all versions greater
than the given version that have

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the same middle digit.

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We can also define ranges using
greater than, less than and

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other comparison operators.

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We can use a tool called semver
calculator to visualize all of this.

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We give semver calculator a package
name and a version number.

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Here it has a popular JavaScript
utility library lodash.

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We'll borrow the rain
from the example below.

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When we enter a range using
a caret in the number 2.2.1,

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all of the minor updates
after 2.2.1 are highlighted.

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Changing this to a tilde highlights
the single bug update for version 2.2.

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The greater than or equal sign gives
us a range of everything beyond and

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including 2.21.

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Notice if we type 0.0,

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most of the packages are highlighted,
but some are not.

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This is because by default,
pre release versions are not included.

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These versions may have experimental
features that aren't added for

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the long term.

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Because of this,

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you'll generally want to avoid using
these versions in production code.

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To review, [SOUND] major changes
are the most important to watch out for

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and may require refactoring.

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Minor changes typically
won't affect your apps.

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Bug fixes are usually beneficial and

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shouldn't have any other
effects on your apps.

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Knowing more about versioning we
can better decide which package and

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version to include in our projects.

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In the upcoming videos, where we learn
more about working with packages,

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we'll also learn how we can install or
update to a specific version of a package.

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This will give you more control over
exactly which code you're using

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in your apps.