data-originalurl,
the URI of a snapshot of that resource created around the time of linking is provided as the value of data-versionurl,
and the linking date is the value of data-versiondate:
<a href="https://www.w3.org/" data-originalurl="https://www.w3.org/" data-versiondate="2024-11-21" data-versionurl="https://web.archive.org/web/20241121100333/https://www.w3.org/"> Robust Link to the W3C home page that supports revisiting the way it looked on November 21th 2024 </a>The
data-* attributes provided on the link can be leveraged by client applications (or manually)
to visit the linked resource, both in its current state (using data-originalurl)
and in the state it was around the time it was linked (respectively using data-versionurl, and the combination of data-originalurl and data-versiondate).
Meanwhile, the URI provided in href remains the default target of the link as was intended by the linker.
As shown in the examples, depending on the motivation for linking, that can be the URI of the resource itself or the URI of a snapshot of the resource.
href attribute for the HTML anchor (<a>) element.
But a link to a resource can be turned into a Robust Link
by including three extension attributes for
that element: data-originalurl, data-versiondate, and data-versionurl.
The use and value of each attribute is as follows:
data-originalurl: REQUIRED - The URI of the resource that motivates the provision of a Robust Link.
In common cases, the default target resource (in href) is also the resource that motivates the provision of a Robust Link.
But, as illustrated by the Examples, interesting scenarios exist in which this is not the case.data-versiondate: REQUIRED - The intended date of linking to the resource,
i.e. the date of the state of the resource that the linker wants the link visitor to be able to experience.data-versionurl: RECOMMENDED - The URI of one or more snapshots of the resource,
optionally accompanied by the date those snapshots were created.
Creation of snapshots of the linked resource is recommended and can, for example, be achieved as follows:
data-* attributes are provided in a machine-actionable manner, as detailed in the below sub-sections,
client applications can be devised that support several pathways to visit a linked resource:
data-originalurl: Visiting the resource in its current state. Cases exist in which that is not be possible
because the resource no longer exists. In such cases, data-originalurl still provides relevant provenance information.data-originalurl in combination with data-versiondate: Finding snapshots of the resource that are temporally close the
intended linking date, in case no snapshots were created around the time of linking,
or in case snapshots that were created become temporally or permanently inaccessible.data-versionurl: Visiting each snapshot of the resource that is listed.data-originalurl in combination with data-versionurl: Finding snapshots of the resource that are temporally close the dates snapshots were created,
in case those snapshots becomes temporally or permanently inaccessible.hrefhref attribute is REQUIRED and its value is as detailed by the pertinent HTML specification.
data-originalurldata-originalurl attribute is REQUIRED. Its value is the URI of the resource that motivates
the provision of a Robust Link. The URI must be absolute, not relative.
data-originalurl="https://www.w3.org/"
data-versiondatedata-versiondate attribute is REQUIRED. Its value is the intended datetime of linking expressed in UTC.
The value can be provided at date or datetime granularity using a choice of two syntaxes: one aligned with ISO8601 and the other following
a convention to express datetimes in URIs that is commonly used by web archives. Valid values are mnemonically shown in the table below and are
formalized in the ABNF for data-versiondate.
| date | datetime | |
| ISO8601 | YYYY-MM-DD | YYYY-MM-DDThh:mm:ssZ |
| Web Archive URI | YYYYMMDD | YYYYMMDDhhmmss |
data-versiondate="2024-11-21" ; data-versiondate="20241121" ; data-versiondate="20241121T162207Z" ; data-versiondate="20241121162207"
data-versiondate must be interpreted as noon UTC of the
indicated date, i.e. YYYY-MM-DD must be interpreted as YYYY-MM-DDT12:00:00Z and YYYYMMDD must be interpreted as YYYYMMDD120000.
data-versionurldata-versionurl attribute is RECOMMENDED.
Its value is a list of one or more URIs of snapshots of the resource that motivates the provision of a Robust Link (see data-originalurl), whereby each snapshot URI may optionally be followed by that snapshot's datetime.
URIs must be absolute, not relative. The provided information elements (URIs and datetimes) must be space-separated. The attribute's value is formalized
in the ABNF for data-versionurl.
data-versionurl="https://web.archive.org/web/20241121100333/https://www.w3.org/ https://perma.cc/44TF-9JXB 20241120164333"
data-versionurl must be interpreted as noon UTC of the
indicated date, i.e. YYYY-MM-DD must be interpreted as YYYY-MM-DDT12:00:00Z and YYYYMMDD must be interpreted as YYYYMMDD120000.
data-versiondate attribute must only be provided at the granularity available to the linker,
i.e. should not be artificially generated on the basis of a known date value.
data-versiondate attribute, client applications may attempt to determine a plausible value,
taking the linking context into account. For example, a client application might decide to use the creation date or last modification date of the
HTML page in which the Robust Link is provided as the value for data-versiondate.
data-originalurl attribute, client applications may attempt to determine a plausible value,
taking the linking context into account.
For example, as shown in the Examples, the URI provided in data-originalurl
commonly, but not always, identifies the same resource as the URI provided for the href attribute.
Therefore, in cases in which data-originalurl is not provided, client applications might decide to use
(the absolute URI rendition of) the URI in href as the value for data-originalurl.
href) is a live web resource,
whereas in Section 4.2. it is a snapshot of a web resource.
href: the URI of the live web resource.data-originalurl: the URI of the live web resource.data-versiondate: the intended date of linking.data-versionurl: the URI of one or more snapshots of the live web resource
and optionally the respective snapshot dates, provided as a list as described above.https://www.w3.org/ on November 20th 2024. On that day,
a snapshot of the resource is created in perma.cc.
Its URI is https://perma.cc/44TF-9JXB and the snapshot datetime provided by perma.cc is
2024-11-20T16:43:33Z.
The next day, an additional snapshot is created in the Internet Archive.
Its URI is https://web.archive.org/web/20241121100333/https://www.w3.org/
and its snapshot date is 2024-11-21.
A
Robust Link to https://www.w3.org/
would be:
<a href="https://www.w3.org/"
data-originalurl="https://www.w3.org/"
data-versiondate="2024-11-20"
data-versionurl="https://perma.cc/44TF-9JXB 2024-11-20T16:43:33Z
https://web.archive.org/web/20241121100333/https://www.w3.org/ 2024-11-21T10:03:33Z">
Robust Link to the W3C home page
</a>
https://www.w3.org/ on November 20th 2024, a very busy day that leaves you with no time to
create any snapshots of the linked resource.
A
Robust Link to https://www.w3.org/ that is less expressive than the one in Example 4.1.1.,
but still supports the creation of alternative pathways to visit the linked resource would be:
<a href="https://www.w3.org/" data-originalurl="https://www.w3.org/" data-versiondate="2024-11-20"> Robust Link to the W3C home page </a>
https://whitehouse.gov was taken over by the new administration.
By that time, the content of the previous administration's White House pages had been moved to https://obamawhitehouse.archives.gov.
A Robust Link to the previous administration's White House page
that expresses provenance and, additionally, conveys snapshots of the very last versions that were available at
https://whitehouse.gov would be:
<a href="https://obamawhitehouse.archives.gov"
data-originalurl="https://whitehouse.gov"
data-versiondate="2017-01-20T12:00:00Z"
data-versionurl="https://web.archive.org/web/20170120160218/https://www.whitehouse.gov/ 2017-01-20T16:02:18Z
https://perma.cc/39FJ-5K7L 2017-01-20T14:26:00Z">
Robust Link to the previous administration's White House page
</a>
exe format
to mp4. One such migrated screencam is https://www.dlib.org/dlib/october99/van_de_sompel/lanlxxx.mp4,
which was derived from the original https://www.dlib.org/dlib/october99/van_de_sompel/lanlxxx.exe.
A Robust Link to the migrated screencam
would be:
<a href="https://www.dlib.org/dlib/october99/van_de_sompel/lanlxxx.mp4" data-originalurl="https://www.dlib.org/dlib/october99/van_de_sompel/lanlxxx.exe" data-versiondate="19991015"> Robust Link to the migrated screencam </a>
http://dewey.rug.ac.be/barn/tex/yfcf.html.
Since they didn't have any copies, they resurrected the site from the Internet Archive, which provides the entry point at
https://web.archive.org/web/19990220153326/http://dewey.rug.ac.be/barn/tex/yfcf.html.
They downloaded the entire site from the Archive, providing a new entry point at https://youngfarmersclaimfuture.info/barn/tex/yfcf.html.
In that page, Robust Links are provided pointing at other pages of the web site, conveying pertinent provenance information.
An example of such a
Robust Link to a resource resurrected from a web archive is:
<a href="https://youngfarmersclaimfuture.info/barn/tex/max.html" data-originalurl="http://dewey.rug.ac.be/barn/tex/max.html" data-versiondate="20150101" data-versionurl="https://web.archive.org/web/19990220013212/http://dewey.rug.ac.be/barn/tex/max.html 19990220013212"> Robust Link to a resource resurrected from a web archive </a>
href: the URI of the snapshot/version that captures the desired state of the resource.data-originalurl: the URI of the web resource for which the URI of a snapshot/version is provided in href.data-versiondate: the intended date of linking.data-versionurl: the URI of one or more snapshots of the live web resource other than the one
provided in href and optionally the respective snapshot dates,
provided as a list as described above.https://www.w3.org/ on that day. In order to do so,
the snapshot https://web.archive.org/web/20241121100333/https://www.w3.org/
is created and its URI is conveyed in the href attribute on the link.
On November 20th 2024 another snapshot has been created in perma.cc and its URI is
https://perma.cc/44TF-9JXB and its snapshot datetime is 2024-11-20T16:43:33Z.
A
Robust Link to the November 21st 2024 version of the W3C home page
would be:
<a href="https://web.archive.org/web/20241121100333/https://www.w3.org/" data-originalurl="https://www.w3.org/" data-versiondate="2024-11-21" data-versionurl="https://perma.cc/44TF-9JXB 2024-11-20T16:43:33Z"> Robust Link to the November 21st 2024 version of the W3C home page </a>
https://en.wikipedia.org/wiki/Web_archiving that is current on that day,
which is
https://en.wikipedia.org/w/index.php?title=Web_archiving&oldid=1258145565.
In this case, a
Robust Link to the November 22nd 2024 version of the Wikipedia page
would be:
<a href="http://en.wikipedia.org/w/index.php?title=Web_archiving&oldid=637465880" data-originalurl="https://en.wikipedia.org/wiki/Web_archiving" data-versiondate="2024-11-22"> Robust Link to the November 22nd 2024 version of the Wikipedia page </a>
https://en.wikipedia.org/wiki/Web_archiving
that was current on April 10th 2012, which is
https://en.wikipedia.org/w/index.php?title=Web_archiving&oldid=485347845.
In this case, the
Robust Link to the April 10th 2012 version of the Wikipedia page looks like this:
<a href="https://en.wikipedia.org/w/index.php?title=Web_archiving&oldid=485347845" data-originalurl="https://en.wikipedia.org/wiki/Web_archiving" data-versiondate="2012-04-10"> Robust Link to the April 10th 2012 version of the Wikipedia page </a>
href: the URI of the snapshot/version that captures the desired state of the resource.data-originalurl: the URI of the snapshot/version that captures the desired state of the resource.data-versiondate: the intended date of linking.data-versionurl: the URI of one or more snapshots of the snapshot/version
provided in href and data-originalurl, and optionally the respective snapshot dates,
provided as a list as described above.https://web.archive.org/web/20241121100333/https://www.w3.org/
existed on that day in the Internet Archive.
In order to do so, a snapshot of the snapshot is created in archive.today.
Its URI is https://archive.ph/T9xD2. Although the snapshot is created on December 9th,
archive.today recognizes it as being a snapshot of a snapshot and maintains the snapshot datetime of the
original snapshot, i.e. 20241121T10:03:33Z. In this case, the
Robust Link to prove the November 21st 2024 snapshot of the W3C page existed in the Internet Archive on December 9th 2024 looks like this:
<a href="https://web.archive.org/web/20241121100333/https://www.w3.org/" data-originalurl="https://web.archive.org/web/20241121100333/https://www.w3.org/" data-versiondate="2024-12-09" data-versionurl="https://archive.ph/T9xD2 20241121T10:03:33Z"> Robust Link to prove the November 21st 2024 snapshot of the W3C page existed in the Internet Archive on December 9th 2024 </a>
data-versiondate, data-versionurl, and/or data-originalurl are provided, web archives must leave the provided attributes and values untouched.
data-versiondate, data-versionurl, and/or data-originalurl are not provided, web archives must not add them.
href attribute, web archives that create a snapshot of that snapshot
must adhere to the Sticky Memento-Datetime and original Link
provision of RFC7089: the Memento-Datetime and the original
link provided in the HTTP header of the former snapshot should be maintained and be provided for the snapshot of that snapshot.
data-versiondate, data-versionurl, and/or data-originalurl are provided, web archives should consider leveraging the provided values for replay.
data-versiondatedata-versiondate attribute are defined by the below ABNF that reuses the following constructs:
date-fullyear, date-month, date-mday, time-hour, time-minute, time-second
from the ABNF in Section 5.6 of RFC3339
data-versiondate = versiondate
versiondate = date / datetime
date = iso8601-date / web-archive-date
datetime = iso8601-datetime / web-archive-datetime
iso8601-date = date-fullyear "-" date-month "-" date-mday
web-archive-date = date-fullyear date-month date-mday
iso8601-datetime = date-fullyear "-" date-month "-" date-mday "T" time-hour ":" time-minute ":" time-second "Z"
web-archive-datetime = date-fullyear date-month date-mday time-hour time-minute time-second
data-versionurldata-versionurl attribute are defined by the below ABNF that reuses the following constructs:
versiondate as defined by the ABNF for data-versiondatescheme, authority, path-absolute, query, and fragment as defined in
Appendix A of RFC3896
data-versionurl = (snapshot-URI *1(SP versiondate)) *(SP URI *1(SP versiondate))
snapshot-URI = scheme ":" "//" authority path-absolute [ "?" query ] [ "#" fragment ]