Help:Page history

A page history shows the order in which changes were made to a TechInfoDepot article or other page on TechInfoDepot. Every editable page on TechInfoDepot has an associated page history (sometimes called revision history or edit history), which is accessed by clicking the "View history" tab at the top of the page.

The page history contains a list of the page's previous revisions, including the date and time (in UTC) of each edit, the username or IP address of the user who made it, and their edit summary. For example, the page history for this help page shows that it was first created on September 20, 2004, and that it had been changed more than 500 times during the next eight years.

Overview
On a history page:
 * All past changes to the page in question are listed in reverse-chronological order.
 * To view a specific version, click a date.
 * To compare an old version with the current version, click cur.
 * To compare a version with its predecessor, click prev.
 * To compare two specific versions, tick the left-column radio button of the older version and the right-column radio button of the newer version, and then click the "Compare selected versions" button.
 * Minor edits are denoted as m.

Below is a detailed example of a page history using the default skin:



Edits are shown from newest to oldest. Each edit takes up one line which shows; time & date, the contributor's name or IP and the edit summary, as well as other diagnostic information. Let's look at some of the functions of this page:
 * 1) The "View History" tab is highlighted and "Revision history" is appended to the page name. Notice that you can't make wikilinks to this extended page name – to make a link to the history page, copy the URL from the browser address bar when viewing the history page, and paste it between single square brackets (external link format) to make the link.
 * 2) The year and month fields allow a quick jump when the page has many revisions. After entering a year and/or selecting a month, click the "Go" button to the right.
 * 3) The "Tag filter" restricts the display to show only those edits that have been tagged by an edit filter. For example, "references removed" may be entered here. After entering a tag name, click the "Go" button to the right.
 * 4) The "deleted only" checkbox will only display RevisionDeleted edits.
 * 5) A line of links to external tools. The available tools vary between wikis.
 * 6) These links take you to the most recent edits (Latest), oldest edits (Earliest) or the next or previous page of edits (Next n / Previous n). Note that the black text in brackets will become links, when applicable.
 * 7) The blue numbers list the number of edits displayed on a page - 20, 50, 100, 250 or 500. A higher number increases the length of a page but reduces the number of pages. The number you select replaces n in the links to the previous or next pages e.g. (Next 100 / Previous 100).
 * 8) (cur) takes you to a diff page, showing the difference between that edit and the current version. The current revision appears below the changes, so you can see how the page is now rendered.
 * 9) (prev) takes you to a diff page showing the changes between that edit and the previous version. The most recent version (the one on the same line as the "last" you clicked on) appears below the changes, so you can see how the page was rendered.
 * 10) The two columns of radio buttons can be used to select any two versions on the page. The current selection is marked by a special background. The two most recent versions are selected by default when you first view the history (that is why they appear framed and have a different background, see horizontal area around 4 and 6). Let's say you want to compare the versions corresponding to numbers 10 & 11 on the image. First, click the left radio button next to number 11. The right column of buttons will then fill as far as number 11. Then click the right button next to number 10. Finally click Compare selected versions. This takes you to a diff page showing the changes between the two versions. The most recent version (in this case number 10) appears below the changes, so you can see how the page was rendered.
 * 11) This gives the time and date of the edit, expressed in local time according to the preference setting. The date and time link to the version of that day and time. Thus the  first line links to the version that was current at the time of loading this revision history, and therefore the result may differ from that of following the link on the page margin to the current version. Even if the page has not changed in the meantime, the  appears.
 * 12) The username or IP  of the contributor appears here.
 * 13) m stands for minor edit.
 * 14) The size of the page in bytes (roughly corresponding to characters)
 * 15) The difference in size between this revision and the previous revision. A green number with a plus sign (+1,864) indicates that the edit added this number of bytes (roughly corresponding to characters) to the page, while a red number with a minus sign (-29) indicates removal. See more at TechInfoDepot:Added or removed characters.
 * 16) This is the edit summary. It is the text the user wrote in the edit summary box (below the edit box).
 * 17) This edit summary begins with an arrow link and grey text. This means the user has only edited a section of the page (named in the grey text). This text is automatically added when you edit a section. A standard edit summary can be added by the user. This appears in black text.

Not shown in this example: some edits may be automatically tagged by the abuse filter (example: (Tag: references removed)); any tags applied appear after the edit summary. Tags cannot be added or removed manually, and are intended to help editors identify potential problem edits for examination; they do not prove that an edit is problematic.

It is possible to restore an old version of a page by following the link to that version, clicking "edit" and then saving. This should be done with caution, as it means that all changes made to the page since the time of that version will be lost.

In rare cases all or part of a page history entry may be shown in grey, struck out by a horizontal line. This indicates that information has been hidden from public view by an administrator or bureaucrat. See Revision deletion and Oversight for more on this.

Searching and exporting histories
The history page contains a link "Revision history search". This links to Wikiblame, a tool for searching the entire history of a given page.

Another useful tool is the Special:Export page, which is used to produce an XML file with the wikitext of the current and (optionally) all old versions of one or more specified pages, with date, time, user name, and edit summary. How the XML file is displayed depends on the browser (it can also be saved locally for later searching and analysis). For more information on this feature, see Help:Export.

The following may also be useful:
 * http://tools.wikimedia.de/~daniel/WikiSense/Contributors.php – a tool to sort the page history by editor and count the number of edits for each editor (works for most Wikimedia sites; can also be downloaded for adaptation to other MediaWiki sites).
 * TechInfoDepot:Usemod article histories – information on retrieving page histories from before January 2002.

Some page histories (such as User talk:Jimbo Wales) are very long, so that paging back even 500 results at a time cannot practically reach a date from several years ago. It is possible to simply change the date (YYYYMMDD) in the URL in these cases ( , for example) to get a listing of results going back from that date.

Web feeds
A link to an Atom web feed for the history of a page is available from the lefthand Toolbox. This gives the diffs of the last 10 edits, each with a link to the ordinary, full diff page. Depending on the browser there may be possibilities such as sorting by author.

An RSS version of the feed can be obtained by assigning to "feed" (one of the ) the value "rss", i.e., by replacing "&feed=atom" with "&feed=rss" in the Atom feed link.

Moved and deleted pages
When a page is moved (renamed), the entire edit history of the article, before and after the move, is shown. The old title becomes a redirect and loses its edit history.

If instead of a move, the entire content was cut and pasted into a new substitute article, the page history gets spread across two articles. The histories can be merged in this case.

When two pages are merged, typically one becomes a redirect. In this case the revision history of the redirect is kept.

When a page is deleted, its revision history remains in the database and can be retrieved by an administrator, who can also undelete the page (see TechInfoDepot:Viewing and restoring deleted pages).

Administrators can also remove selected revisions from a page history, for example if they contain defamatory text. For details, see Selective deletion.

Image histories
An "image" (in the broad sense of an uploaded file) can be edited, or, more generally, be replaced by a different image, by uploading a new image file with the same name. Again all versions are kept. The image history listing forms part of the image description page, which appears when clicking on the image. The image history consists of this and the old versions themselves.

Images which have been deleted from their source are not available (not to be confused with images removed from an article but not from their source), the only record available is the upload log, deletion log and possibly the "votes for deletion" archive. Neither the latest nor older versions are kept by the system, hence it is not possible to restore a deleted image without uploading it again.

Linking to a specific version of a page
It is sometimes useful to link to a specific version of an article - this is called a "permanent link". For example, one might have done a review of a TechInfoDepot article and want to indicate which particular version was reviewed.

A permanent link to the current version of an article is normally available from the sidebar, under Toolbox -> Permanent link. For other namespaces, or if the version to be linked to is not the current version, use the page's History tab to navigate to the specific version required. The URL here will be suitable for use to permanently reference this version, and can usually be obtained from the browser's location bar. See also URLs of TechInfoDepot pages.

However the permalink does not guarantee to display the coherent historical version of any page, except for very simple pages; this is because most pages include images, templates (transcluded text and images), or time-based variables (such as CURRENTTIME ). All these elements are not retained using a "permanent link" and they will be rendered according to the current state of the image/template, or the current time, producing a different result than was rendered at the time the old version was saved. Only the main text of the article is retained correctly, that is, the wikitext that one sees when clicking Edit.

One way to retain a visual snapshot of the current version is to make a web mirror of it, that is to copy the HTML file of the page, together with the auxiliary files such as cascading style sheets or images. Other ways are described in Help:Downloading pages.

Copyright status of old page revisions
TechInfoDepot does not give legal advice.

The Wikimedia Foundation wishes to make users of historical versions of articles aware that some of the history may be problematic and not necessarily reliable.

Title 17 United States Code § 108 archive notice: page histories should be considered not-for-profit archival material. Although all contributions are supposed to be compatible with CC-By-SA, it is possible that a user has inserted something which is a violation of copyright, in which case the user had no right to release it as CC-By-SA. In these cases, TechInfoDepot does not have a general policy of always deleting all copyright problems from the history, particularly if the edit is made to an existing article rather than a new one, although such material will be removed from the current version of a page. In the event of a DMCA takedown notice, the Wikimedia Foundation may remove violating versions from the page history. In other cases, the version may be kept to allow proper tracking of authors and demonstrate compliance with all legal requirements. You are being given notice under Title 17 that you are responsible for complying with copyright laws in regards to archival material, and that not all versions in a page history are necessarily available under the CC-By-SA.

As noted at the end of each history revision, in the text at MediaWiki:history copyright, the page histories may contain material that is subject to copyright limitations. While we attempt to remove such material from the current version (see copyright problems) it is kept in the history for research and author attribution purposes. As Wikimedia is a not-for-profit company, this is believed to be fair use.

See also TechInfoDepot talk:Copyright violations on history pages for further discussion of this point.