Microsoft is splitting AI training from AI grounding, and only training can be set in robots.txt. Sites relying on NoArchive or NoCache have until 1 March 2027 to re-register or default to Allow.
Microsoft has announced new preferences to replace the two tags publishers used to limit AI use of their pages. The old tags stop being read as preferences on 1 March 2027, or sooner where Bing detects a new preference. The announcement sets a timetable; the changes are not live yet.
In a 30 October Bing blog post, Krishna Madhavan, a Principal Product Manager at Microsoft Bing, said new preferences are honoured from 1 February 2027. Nothing changes today.
The two new preferences
The first preference, AI Training, is a robots.txt token for a site or a path, with a page override in a meta tag or header. It is the token OpenAI and Google also said they would support, from the Internet-Draft the Bing post links.
The second, AI Grounding, is Microsoft's own and works only on a page. Grounding means using content to help inform AI-generated responses. Its values are Allow, Disallow and a new DisallowExtended.
DisallowExtended limits use to experiences Microsoft operates, such as Copilot and Microsoft 365. It excludes third party services such as Web IQ and API access in Foundry.
Microsoft states that "there is no site-wide robots.txt grounding preference". Both preferences default to Allow.
What refusing costs
Refusing has a stated cost to visibility in AI answers. Disallowing grounding "will significantly reduce your content's visibility in AI-generated experiences, without affecting eligibility for Bing search results".
Microsoft's own example of independence is Training on Disallow with Grounding on Allow. Content then can inform answers without being used to train generative models.
The four dates
On 15 December 2026, temporary grounding preferences open in Bing Webmaster Tools, only for sites using NoArchive or NoCache that day.
Microsoft starts honouring the new preferences on 1 February 2027, 48 days later on CTOL's count.
A site on NoArchive or NoCache that wants to keep its grounding limits must, by 1 March 2027, publish the page preference and record a temporary one in Webmaster Tools. That is 28 days on.
Temporary preferences expire on 30 September 2027, or sooner when a page is recrawled.
Missing 1 March has a stated cost. Pages still using NoArchive or NoCache then "default to Allow for grounding until Microsoft recrawls them". For training, "there is no temporary training setting in Bing Webmaster Tools".
Publishing a page setting does not activate it. Microsoft must crawl the page to discover the setting, and IndexNow, a signal that a page changed, raises the chance of a recrawl without guaranteeing a date. The settings govern use, not crawl access, so an Allow does not override a robots.txt rule blocking Bingbot.
Microsoft leaves one interaction unexplained. The post says that on detecting a new training or grounding preference on a site, it will disregard any NoArchive and NoCache preferences left there. It does not rank that rule against the temporary preference, so whether a site adding only the training token loses a legacy grounding limit first is open.
CTOL's assessment and what to watch
CTOL sees a risk for sites that keep legacy tags and take no action by 1 March 2027: Microsoft's default for them is Allow. The evidence is that default, the single temporary route for grounding and none for training.
The indicator is each site on the legacy tags completing both steps by that date: the page preference and the Webmaster Tools record. That is what the post asks of such a site. It does not show that any AI answer respects the restriction.