clos-diff is a GPL licensed library which will be able to create and apply diffs of CLOS objects in a compact representation that will not use too much bandwidth or disk space. The library also preforms the diffs recursively, so that (theoretically) infinite layers of objects can be diffed. The only dependency is closer-mop. The API is simple, and documented below: function: clos-diff:diff (old new &key (test #'equalp)) This function will create a diff that represents the modification that need to be applied to object old to create the object new. The test parameter will control the test used for equality. As a special case is the old parameter is nil, a diff from an object with no bound slots will be created. function: clos-diff:apply-diff (diff &optional object) This function will apply the diff given in the parameter diff to the object contained in object. If object is nil, a fresh object of the appropriate type (with all slots unbound) will be created, and the diff will be applied to that (See the documentation for diff for more information). This project is hosted on github. Submit bug reports there. Also, you may contact the author at krzysdrewniak AT gmail DOT com .