@vampirehunter, In addition to Jacks observations: Ultimate SEO URLs 2.2 by Chemo: Pro:           Easier installation – less file changes           All included in one class file Contra:           Only one cache option: file cache – not sure if it’s a con           Limited character encoding to ISO-8859-1 or other ISO character encodings at least in the actual version.  I posted the fix for full utf-8 support here:           Character conversion pairs are only possible to define generic for all store languages. Some special characters have different transliterations in different languages. Example: “ä” should be transliterated to “ae” in German, but to ” a” in Turkish, “ü” should be transliterated to “ue” in German, but to “u” in Spanish and Catalan.           In Multilanguage store the secondary language URLs are built only by the categories and products title translations, no specific language part in the path. Switching from one language to another is done like in core adding language html parameter to the URL (?language=de) which disappears once the language has been changed.          No html language tags can be realized because of this. Google doesn’t validate html parameter for html language tags         Additional custom pages are more difficult to add, even support for the most common add-ons which use additional pages, is included.   Ultimate SEO URL5 BS: Pro:           4 cache options, but sql cache got vulnerability issues reported by @Gergely:  https://forums.oscommerce.com/topic/336702-ultimate-seo-urls-5-by-fwr-media/?do=findComment&comment=1757817           Claims to be faster than ULTIMATE SEO URLs 2 by Chemo, but I can’t check or confirm this point           Full utf-8 character encoding support           Separate character conversion lists for each language, so this can be realized: Example: “ä” should be transliterated to “ae” in German, but to ” a” in Turkish, “ü” should be transliterated to “ue” in German, but to “u” in Spanish and Catalan.           In Multilanguage store the secondary language URLs are built by permanent language shortcut in the paths. Example: www.mystore/de/meine-kategorie-c-153.html , www.mystore/es/mi-producto-p-53.html           html language tag support already included since BS version.           Additional custom pages can be easy added copying and modifying an existing page file.    Contra:        installation requires a bit more file changes        a lot of separate files -> more complicate to customize if needed.        the issues mentioned by Jack   For sure there are more things, maybe other users can extend the list. My recommendation – Resume: for one language stores I recommend ULTIMATER SEO URLs 2.2 by Chemo, for multilanguage stores and specifically stores in languages which include critical special character issues, ULTIMATE SEO URLs5 BS. Hope this helps Rainer