MUM (Multitask Unified Model)
MUM, short for Multitask Unified Model, is an AI system Google built that can both understand language and write it. Google's guide to its ranking systems says MUM isn't used for general ranking in Search. Google uses it for a few specific jobs, like improving searches for COVID-19 vaccine information and the callouts it shows in featured snippets.
Source: Google Search Central, A guide to Google Search ranking systems, checked October 29, 2026
What MUM (Multitask Unified Model) means for your business
Google announced MUM in May 2021 with a hiking example: someone who'd climbed Mt. Adams asking how to get ready for Mt. Fuji. Google said MUM was trained across 75 languages, could read text and images together, and would power new features over the coming months and years.
Many of the pages that still come up for MUM date from 2021 and treat it as a ranking update every site had to get ready for. Google's own guide says something narrower today. So we wouldn't rewrite a page for MUM, and we'd read any advice to "optimize for MUM" as a 2021 idea.
The habit behind Google's example still holds. Buyers ask long questions with a few smaller ones tucked inside, like which month is best to go, what gear to bring and how hard the climb is. If your pages only answer the short version of what buyers ask, making your site answer the whole question for Google and AI tools is where our work begins.
Source: Google, MUM: A new AI milestone for understanding information (May 18, 2021), checked October 29, 2026
Last reviewed October 29, 2026. All terms
How AI answers it today
On October 29, 2026, Google's AI Overview described MUM as a tool for complex searches, citing agency posts, LinkedIn and YouTube but no Google page. ChatGPT cited Google's 2021 announcement. Neither said Google's guide now limits MUM to a few specific jobs.
Our run through ChatGPT and Google's AI Overview, October 29, 2026. A sample, not what every buyer sees.
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