Mobilegeddon is the informal name given to Google’s April 2015 algorithm update that began using mobile-friendliness as a ranking factor for searches made on mobile devices. The nickname — coined before the update rolled out — reflected industry fears of catastrophic ranking drops for sites that had not built responsive or mobile-optimised versions. The update affected only mobile search results, not desktop rankings, and applied at the page level rather than the site level. In practice the immediate impact was less dramatic than anticipated, partly because many of the worst-affected sites were already ranking poorly. Mobilegeddon was the precursor to mobile-first indexing, Google’s more fundamental shift (completed by 2023) to using the mobile version of a site as the primary basis for all indexing and ranking.