A useful tool to see what changes have been made to a Wiki page.
To see just the most recent change to a wiki page, click on the date of that change at the bottom of the page or click on the time since the change as reported in Quick Changes. A neat and useful feature but hardly an intuitive user interface, or one that is documented in an obvious place. Both link to Quick Diff. Note that the latest change is not necessarily the latest significant change.
Note that if the same user makes two or more changes in succession; the Quick Diff algorithm considers those a single change. However, if a different user/IP makes a change, then the baseline for Quick Diff resets.
To use manually, edit the page URL replacing the word "wiki" with the word "quickDiff". This shows who made the change, and what exactly was changed. Much prettier than using "copy=".
Quick Diff is under-rated
For people not used to following every change on C2, Quick Diff can be a hidden gem because of the converse of One Mans Meat Is Another Mans Poison. I find valuable information in what people throw away, enough times that I sometimes become overly hesitant in adding changes of my own (often I do a Quick Diff first before changes).
I just held back on updating Leadership Ideals because Quick Diff gives me a name of a Wiki Zen who had interests and expertise in the subject area. Even though the change was made 5 years ago, my additional would have spoilt the presentation of the amount of work done then. So I chose to update the LeadShip page instead as its Quick Diff was already spoilt on an earlier occasion (by me).
It annoys me when Quick Diff gets spoilt by the Spammers, e.g. BobbyWoolf page.
Aug05 update. Just bumped into a page that supports my love for Quick Diff. It has not changed for seven years and last change has significance. -- dl [Bowdlerized to preserve the edit in question]
Had The Last Word - seeking a better way to make use of Quick Diff even without versioning
Earlier I said
Earle you probably know I am a big fan of Quick Diff as I have said so at C2 more than once. And I am also aware that you do not like me going about adding to highlight previous "important" change on a page. Is there another way to have something similar to "versioning / highlighting"? I made this as I just changed Signed Witha Purpose, I think it was important that CC remark be removed from that page, but by doing so I removed equally important observation (in Quick Diff) in response to a contribution from another wiki participant.
a previous example is the differences with CC in regards to Soa Is Night Sky. I wanted to update CC homepage (he started it and obviously wanted some response) but then the Quick Diff showed he had what looks like unfinished dialogue with another person. I did not want to be rude and therefore talk to CC on my homepage, which later (eventually) led to On David Liu Discussion.
for now I would still do my "awkward" last change type thing, only much less frequently. Sometimes I resort to not editing a page, or find another page to edit.
-- David Liu
I think the solution here is to keep content in a consistent state that can be interpreted without the use of Quick Diff. It only takes a spelling correction to "remove" an important change from the diff display; therefore the tool is too fragile to be relied upon. Does it really matter enough when some contributions were made that they need to be Time Stamped? I don't think so; they can be brought to prominence by careful application of Refactoring Wiki Pages, Wiki Tagging or similar (although bear in mind Gently Reduce Wiki Badges). The profusion of what can only be described as metadata only makes pages more visually noisy and harder to read for those who are not interested in it. -- Earle Martin
If the Quick Diff does not show anything, someone probably just corrected broken tabs by turning
this
into
that
Wouldn't a blank Quick Diff also show up if someone made a change, then subsequently reversed the change?
Yes.
If Quick Diff is just showing you the Wiki page, your URL is malformed. It should look like this: c2.com 
.
Some manglings of Wiki URLs let you browse just fine, but fail for Quick Diff (and maybe other scripts). [Has it been fixed?] No - e.g., if you replace '/wiki' by '/wiki/wiki'.
When a visitor saves a changed page, wiki keeps a copy of the old page. Clicking on Quick Diff for a page runs the diff utility with the previous version and the current version, does some trivial post-processing of the output, and returns it to the browser.
BTW, the previous version's version number is not necessarily one less than the current version's version number.
Diff Algorithm is a treasure house
I have been told pseudocode (small algorithm) exists in that page that works well in real life
Additionally let me note that, for decades now, people have implemented what they call "diff", but which is uninformed by the state of the art even as of 1975, and such naive diff algorithms turn out to truly suck in real world application. The Diff Algorithm page describes approaches that truly work in a non-naive sense.
Q How do I do a Quick Diff between two earlier versions for a Wiki Page, if the changes were made in the current month and I do not want to copy out and do manual Quick Diff?
A See Wiki History Scripts.
A Use the recently introduced Hist Diff.
Question about missing numbers moved to Hist Diff.
Viatasso Wiki has a neat spin on Quick Diff: instead of showing only the diff listing, the diff is integrated into the page view by appearing as highlighted text within the page. Users can also choose in Preferences to highlight all changes made by a user or only the latest changes by anyone. If you choose the first alternative, when X writes all their changes will be highlighted as long as they are consecutive, as long as X will keep on making edits.
This feature is descended from Richard Drake's original implementation in the software for Why Clublet.
Anybody have any comments on Win Merge's comparing utilities?
Yes, it works great to find exactly what was changed on a Wiki Page when things are complicated because of software short-comings (little bit of a hassle to pull pages out of history). Would be nice if Wiki used these types of advanced tools (not easy to implement, but nice).
Suggestion for an improved quickDiff: Make the User Name (if present) a clickable link.
Quick Diff is broken this morning! Returns "not found" (404?) for "/cgi/quickDiff"!
(Still nothing in Wiki Wiki System Notice about Quick Diff not working. )-:
See also: Hidden Features, Zero Diff, Diff Algorithm
See original on c2.com