Basic use

1 Raw data. Click on the results with a coloured background to see the raw IANA data for a subtag.

2 Find. The description is the name of the subtag, ie. the language, region, etc. You can search on any part of a description (eg. eng gives results that include Bengali, English and Tengwar). Note that some languages may be spelled differently, eg. Panjabi yields three results, but Punjabi only one.

3 Look up. Looks up all forms of all subtags in the list, eg. it returns both a language and extlang subtag for cmn, and it returns both language and region subtags for the CA in en-CA. Subtags can be separated by commas, semicolons, hyphens, or spaces, eg. en; fr, ca, Bali-1901.
Only exact matches of subtags are returned, ie. ak doesn't match akk.
If there is no output for a tag, it was not a valid tag in the registry.

4 Check. Looks up all subtags in a language tag (ie. a hyphen-separated list of subtags) and reports problems, if there are any, eg. de-419-DE-alt and ms-cmn.
Warnings are also displayed to guide you in language choices. Example: ms-min-Latn.

5   provides a link from a language subtag entry to the Character Usage app. This provides details of characters used by the language, often in multiple orthographies. Macrolanguages have redirects to child languages in the Character Usage app.

6   provides a link from a language subtag entry to the SIL Ethnologue. This is useful when trying to find a language. If there is no page for a given language tag, such as nn, click on the result to reveal the full record; if there is a macrolanguage specified, eg. 'no', that will probably yield an ethnologue entry.

7   provides a link from a script subtag entry to the most relevant Unicode script block in UniView.
In some cases, there are additional Unicode areas dedicated to the same script. These can usually be easily found alongside the current block in UniView's pull-down control.
Some very large blocks such as Han, Hangul and Egyptian Hieroglyphs are not linked to. Other scripts do not yet have Unicode blocks.

8   provides a link from a language or script subtag entry to search Wikipedia. It uses the description as the search key.

9 Grandfathered tags are pre-RFC 4646 registrations of tags that cannot be completely composed from the subtags in the current registry. If you search for a grandfathered tag it will be displayed in the results, and the subtags that are in the current registry will also be shown.

10 Redundant tags are pre-RFC 4646 registrations of tags that can now be formed by combining separate subtags from the current registry. They do not show up in search results.