GeezerVison

Unchanged paragraphs appear with a subtle grey background and a grey border. (Note that not all paragraphs are shown; only some of those surrounding the changes). Modified, moved, deleted, and inserted paragraphs all have a transparent background, a coloured border, and a symbol to the left of them. Such paragraphs on the left (from the older version) are given a yellow border colour, and carry a minus symbol (−), with the exception of moved paragraphs which carry a right-facing arrow symbol (↪). Similarly, such paragraphs on the right (from the newer version) are given a blue border colour and carry a plus symbol (+), unless it's a moved paragraph, in which case it carries a left-facing arrow symbol (↩). Note that these arrow symbols can be clicked on to jump between the moved-to and moved-from locations.

When a paragraph is recognised as having been modified or moved, any text deleted from the original paragraph is highlighted in bold-yellow on the left, and any text inserted is highlighted in bold-blue on the right. Where an old paragraph is deleted entirely, or an entirely new paragraph is inserted, no such bold-colour highlighting is done to its entire text. New, deleted, and moved paragraphs will be seen to have an empty entry opposite them.

Beware that diff algorithms are not perfect. Presenting perfect diffs for every possible combination of changes is difficult, with compromises often having to be made. Consequently sometimes changes may fail to be recognised as a modification or move of an existing paragraph, and thus appearing instead as a pair of deleted and inserted paragraphs.

The links "Revision as of date" link to each version. If the newer version is the latest one, the link will be to the usual page and the wording will be "Current revision (date)" instead.

The "(edit)" link will take you to the page for editing that version. You may be warned that you are editing an out-of-date revision; if you ignore this and continue, you will revert all the edits made since that revision.

The "(undo)" link on the newer revision's side will revert that specific edit. When you click the link, you can check the diff page of the edit you are going to make, and the edit summary will be automatically filled in with the phrase of MediaWiki:undo-summary (Undid revision $1 by $2 (talk)). This summary can be edited before you submit your edit. When you are undoing several edits at once, the auto-summary may not work. Though the link exists on all diff pages, it does not function when the revisions conflict. Often, versions older than the current one cannot be undone in this way. If it does not work, you will be told that the edit could not be undone and end up on the regular editing page of the current version.

The "(thank)" link is only displayed when both the viewer and editor are registered users. It can be used to thank the editor.

Below that are links to the user page and talk page of each user who edited the older or the newer versions. Links to the users' contribution lists are also shown. For administrators and rollbackers, a "[rollback]" button also appears where applicable, allowing them to revert all the edits made by that user.

Then the edit summaries are shown in parentheses. If the user has used links in their edit summary, these act as links on the diff page as well. If the editor marked the edit as a minor edit, m appears before the summary.

The "Previous edit" and "Next edit" links lead to earlier or later diffs. When you are viewing the diff between two non-consecutive versions of a page, you will also see the message "(x intermediate revisions not shown.)".

After the table of differences, the latest of the two compared versions is shown fully, unless you have specified in your preferences that this is not to be done.

Typically the revision shown on the left of a diff page will be the older of the two revisions. Technically however, strictly speaking this may not necessarily always be the case. For prev, next, and cur forms of diffs, or diffs resulting from the radio controls in a page's history, the older of the two revisions is indeed always going to be on the left. However, things can get less certain when it comes to user generated diff links, since it's easy to make mistakes, and the behaviour of the diff page may be surprising.

As discussed later in the linking section, fundamentally, the diff page shows a difference with respect to a base revision specified via an oldid parameter. When the diff URL specifies another revision ID to be compared against the specified base revision, the diff page always assumes that the base will be the older of the two revisions and thus always places it on the left. (Or at least this is the case in early September 2026). Consequently, diff links should always be constructed with the older revision ID (the smaller number) specified as the base ID, and if this is not done so, then the resulting diff may appear backwards and confusing. You can spot such a situation either by the base revision ID in the URL being a larger number than the other ID, or more simply by the date of the revision on the right being older than the one on the left. You can correct it simply by swapping the two IDs in the URL.

Use of diff links does not necessitate understanding of them, but understanding them may aid you in producing correct links that show what you intended for them to show, especially with the preferred link construction methods to be used within wikipedia, and it's more simple than you might realise.

There are three key parameters relevant to diffs:

• oldid: This is used to specify the unique ID of a particular revision of a page to base the diff on.
• diff: This is used to specify what to compare the specified revision with. This can contain values of either prev, next, cur, or another revision ID.
• diffonly: This is optionally used to control whether or not a preview of the page is shown beneath the diff. By default a preview is shown. This parameter can be added with a value of 1 if the preview is not wanted.

The values prev (meaning previous) and next for the diff parameter are used to compare the revision specified in oldid with the singular revision that either preceded it, or succeeded it, respectively. I.e. prev compares the revision with one revision backwards in time, while next compares with one revision forward in time. In the prev case, the specified revision is shown on the right hand side of the page, while the opposite is true for next. Note that if no previous or next revision exists, respectively, then the diff will simply indicate that no difference exists. If diff is set to a revision ID, while no oldid param is provided, then this is treated as though the ID had been specified in oldid and diff was set to prev. (Note that alternatively, if oldid is specified alone, without a diff parameter, then the old revision of the page will be presented rather than a diff).

A diff is not limited to comparing just a pair of revisions that are directly adjacent in history; it can compare any singular revision with any other. When diff is set to cur (meaning current), then the revision specified with oldid is compared with the very latest (current) revision of the page. When diff is instead set to a revision ID, then similarly the revision specified with oldid is compared with the revision specified by diff. Note that in the latter case the diff revision is expected to be a newer ID than that specified by oldid. If this expectation is not honoured, then the presented diff may appear confusing, since the revision specified by oldid is presented on the left hand side of the page even if the diff ID were actually older, resulting in a presentation that appears backwards. Note that if both revision IDs are the same, then the diff will state that no difference exists.

Note that diff comparisons are not even limited to revisions from the same page. A revision ID from a different page can be specified in diff and the diff will simply present a comparison of the content of the two pages as they were at those two points in time. The page name displayed at the top of the diff will be shown in the form Page-name-A and Page-name-B in such a scenario.

If either oldid or diff is set to a revision ID that does not exist, then an error will be displayed.

For linking to a diff from outside of wikipedia, or where otherwise permissible within wikipedia, full links (URLs) take the example forms below. When exploring page history these can be copied directly from the address bar in a web browser, or from right clicking on a diff link and selecting 'copy link'. Note that, as mentioned above, within wikipedia it's preferable to avoid full URLs whenever possible, using the alternative internal linking methods discussed below instead.

Beware that if/when using a full URL within wikipedia, if you just paste the raw link, the full URL will be used as the display text for the link (e.g. https://en.wikipedia.org/w/index.php?title=apple). These can be long and unwieldy. If you put a pair of square brackets around it, like [https://en.wikipedia.org/w/index.php?title=apple], then the displayed text will appear like . If you also include a space and then some text inside the brackets, after the URL, then that text will replace the number as a display label for the link. For example, [https://en.wikipedia.org/w/index.php?title=apple the apple article] becomes the apple article.

The following examples use 54321 as an example oldid revision ID, and 123456789 as an example newer diff revision ID. Note that while many wikipedia URLs include a title parameter to specify the name of a page, like in the previous paragraph, and while this often can be found within diff URLs, this isn't strictly required to be present in a diff URL, and is excluded from them in the following examples.

Diff links can be created within wikipedia using the special [[Special:Diff/oldid]] and [[Special:Diff/oldid/diff]] link formats. Use of this form, or the {{diff}} template discussed below, should be used whenever possible within wikipedia, for the reasons mentioned earlier. Note that unlike {{diff}}, this form works within edit summaries. Note also that, as with other double-square-bracket link forms, you can add a pipe (|) character followed by some text, before the closing pair of brackets, to specify a nicer display label for the link (i.e. like [[Special:Diff/oldid/diff|my diff link]]).

As demonstrated in the examples, when a URL has diff set to prev, or where diff specifies a revision ID and oldid is unspecified, the singular revision ID on its own suffices within the special link. Otherwise, when copying parameters from a URL, care needs to be taken to not just copy the oldid revision ID, but the accompanying next, cur, or revision ID detail from the diff parameter too, else the resulting diff might not be what you expect.

The {{diff}} template provides an alternative to the special diff links just described. These may appear cleaner, and may be easier to memorise, however beware that they do not work within edit summaries (templates are not expanded within edit summaries, instead just appearing as written).

The general syntax is:

{{tlx|Diff|title|diff|oldid|label|diffonly=yes}}

The title parameter is the title of the relevant page (optional in most cases). The diff and oldid parameters are as previously discussed. The label parameter is to specify an optional display label for the link (without one a number will be used). The diffonly=yes parameter is optional, and as discussed earlier, can be added to avoid including a page preview in the diff.

The {{URL to diff}} template provides a means of creating an instance of a {{diff}} template directly from a full diff URL, without having to manually construct one by extracting parameter values.

The syntax is:

{{Subst:URL to diff|url=diffurl|label=mylabel}}

Where diffurl should be replaced with the full URL, and mylabel should be replaced with a display label for the link.

Note that as demonstrated, use of this template needs to be substituted.

As an example, {{Subst:URL to diff|url=https://en.wikipedia.org/w/index.php?oldid=54321&diff=prev|label=my diff link}} will produce a link like this: my diff link