Editing Namespaced Identifier (NSID) (section)

== Structure ==
NSIDs follow a reverse domain-name pattern followed by a name segment:<syntaxhighlight lang="text">
tld.domain.name
</syntaxhighlight>For example, <code>com.example.fooBar</code> would be a valid NSID, with <code>com.example</code> being the domain name and <code>fooBar</code> being the name segment.

This structure ensures that organizations can create identifiers within their own controlled namespace, preventing naming conflicts across the protocol.

=== Syntax ===
NSIDs must adhere to specific syntax rules.

In the overall structure, the NSID must:

* Contain only ASCII characters
* Have at least 3 segments separated by periods
* Contain a maximum length of 317 characters

In the domain authority portion, the NSID must:

* Be in reverse domain-name order (e.g. <code>com.example</code> instead of <code>example.com</code>)
* Have at least 2 segments
* Contain a maximum of 253 characters (including periods)
* Contain only lowercase letters, digits, or hyphens (cannot start or end with hyphens)
* Must not start with a digit

In the name segment, the NSID must:

* Be 1-63 characters long
* Contain only letters and digits (case-sensitive)
* Must not start with a digit

=== Variations ===
NSIDs can be extended with:

* '''Fragments''', using a hash symbol to reference specific definitions within a schema (e.g. <code>com.example.defs#userView</code>), 
* '''Glob patterns''', using an asterisk to match multiple NSIDs (e.g. <code>com.atproto.*</code>)