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@@ -220,6 +220,26 @@ You can also store any information you like from your controller.  Just override
 Remember to add those extra columns to your `versions` table ;)
 
 
+## Diffing Versions
+
+When you're storing every version of an object, as PaperTrail lets you do, you're almost certainly going to want to diff those versions against each other.  However I haven't built a diff method into PaperTrail because I think diffing is best left to dedicated libraries, and also it's hard to come up with a diff method to suit all the different possible use cases.
+
+You might be surprised that PaperTrail doesn't use diffs internally anyway.  When I designed PaperTrail I wanted simplicity and robustness so I decided to make each version of an object self-contained.  A version stores all of its object's data, not a diff from the previous version.
+
+So instead here are some specialised diffing libraries which you can use on top of PaperTrail.
+
+For diffing two strings:
+
+* [htmldiff](http://github.com/myobie/htmldiff): expects but doesn't require HTML input and produces HTML output.  Works very well but slows down significantly on large (e.g. 5,000 word) inputs.
+* [differ](http://github.com/pvande/differ): expects plain text input and produces plain text/coloured/HTML/any output.  Can do character-wise, word-wise, line-wise, or arbitrary-boundary-string-wise diffs.  Works very well on non-HTML input.
+* [diff-lcs](http://github.com/halostatue/ruwiki/tree/master/diff-lcs/trunk): old-school, line-wise diffs.
+
+For diffing two ActiveRecord objects:
+
+* [Jeremy Weiskotten's PaperTrail fork](http://github.com/jeremyw/paper_trail/blob/master/lib/paper_trail/has_paper_trail.rb#L151-156): uses ActiveSupport's diff to return an array of hashes of the changes.
+* [activerecord-diff](http://github.com/tim/activerecord-diff): rather like ActiveRecord::Dirty but also allows you to specify which columns to compare.
+
+
 ## Turning PaperTrail Off/On
 
 Sometimes you don't want to store changes.  Perhaps you are only interested in changes made by your users and don't need to store changes you make yourself in, say, a migration -- or when testing your application.