See MARC21 for detailed descriptions of 856 indicator values and subfields.

The most commonly used 856 indicator values in UNBIS are:

First indicator = 4 (indicates that the access method to the electronic resource is through HTTP)
Second indicator = 1 (indicates that the location in field 856 is for an electronic version of the resource described by the record).

When the location in field 856 is for an electronic resource that is related to the bibliographic item described by the record, then the second indicator value is 2.

The following 856 subfields are recorded in UNBIS:

$3 Specifies the part of the bibliographic item to which the 856 field applies, language versions, etc.
$q Type of electronic format, e.g. PDF or HTML.
$u The URL or Uniform Record Locator, the specific address that is used to locate web pages on the Internet.

Automatically-generated 856 fields for UN documents

For UN documents that are available on the Official Document System (ODS), an 856 field for each language version of the document is added automatically to bibliographic records, providing direct links to the ODS texts.

For these automatically-generated 856 fields, a 500 note is not added to the bibliographic record indicating that the text is available on the ODS.

856 fields are only added manually to bibliographic records for UN materials when the texts are not available on the ODS, but may be found at the website of the issuing body.

Examples:

500 $a Available also at UNICEF Innocenti Research Centre website (viewed 20 June 2007).
856 41 $3 English $q PDF $u http://www.unicef-icdc.org/publications/ pdf/insight7.pdf
856 41 $3 Français $q PDF $u http://www.unicef-icdc.org/publications/ pdf/insight7f.pdf

500 $a Abstract available at CDRI website (viewed 20 June 2007).
856 42 $3 Abstract: English $q HTML $u http://www.cdri.org.kh/webdata/workpap/wp06-abs.htm

191 $a A/58/99
856 41 $3 العربية $q PDF $u http://daccess-ods.un.org/access.nsf/Get?Open&DS=A/58/99&Lang=A
856 41 $3 中文 $q PDF $u http://daccess-ods.un.org/access.nsf/Get?Open&DS=A/58/99&Lang=C
856 41 $3 English $q PDF $u http://daccess-ods.un.org/access.nsf/Get?Open&DS=A/58/99&Lang=E
856 41 $3 Français $q PDF $u http://daccess-ods.un.org/access.nsf/Get?Open&DS=A/58/99&Lang=F
856 41 $3 Русский $q PDF $u http://daccess-ods.un.org/access.nsf/Get?Open&DS=A/58/99&Lang=R
856 41 $3 Español $q PDF $u http://daccess-ods.un.org/access.nsf/Get?Open&DS=A/58/99&Lang=S
[856 field automatically added for a UN document available on the ODS]