Right now, MediaWiki has 2 pure-PHP engines to produce diffs (there's also a native PHP extension wikidiff2, but we're not discussing it right now): * DairikiDiff is what everybody uses, and * Wikidiff3, and alternative implementation by Guy Van den Broeck that was around for 8 years but required a configuration change While less battle-tested, Wikidiff3 offers vastly improved performance on heavy diffs compared to DairikiDiff. The price, however, is that it makes certain shortcuts if the diff is too complex. I ran through 100K diffs from English Wikipedia, and 6% of diffs were different. Lots of changes were seemingly insignificant but I need your help with determining if it's really so. I've built this tool <https://diff-forge.wmflabs.org/wiki/Special:DiffCompare>[1] to facilitate the comparison. It displays two diffs from different algorithms side by side (yeah, it can get too wide, I know:P). Which of them is which is random. Parts with differences between the implementations are highlighted in yellow. Below is the diff of differences for the reference. You can vote with buttons above the diffs, no registration is required. If you see a catastrophically bad diff please send me the link. Unless the results are significantly worse, I'd like to go ahead and make wikidiff3 the only implementation. [1] https://diff-forge.wmflabs.org/wiki/Special:DiffCompare -- Best regards, Max Semenik ([[User:MaxSem]])