Home Slack faces backlash over user data used for AI and machine learning training

Slack faces backlash over user data used for AI and machine learning training


  • Slack uses customer data to power ML features, causing criticism due to confusing policy updates and opt-out processes via Slack admins.
  • Slack clarified that anonymized data is used to improve search and recommendations, but not for premium AI tools or third-party training.
  • In response to backlash, Slack emphasized that its models do not memorize or reproduce customer data, addressing community concerns.

Slack has reportedly been using customer data to power its machine-learning (ML) features, such as improving search result relevance and ranking. This has sparked criticism due to confusing policy updates, which led many to think their data was being used to train AI models.

As per the company’s policy, anyone who wishes to opt out must request their organization’s Slack admin to email the company to stop the use of their data.

The revelation comes as Corey Quinn, an executive at Duckbill Group, wrote on X asking, “I’m sorry Slack, you’re doing f**king WHAT with user DMs, messages, files, etc?”

(Tweet from Corey Quinn and Slack's Response):Corey Quinn (@QuinnyPig) tweeted on May 16: "I'm sorry Slack, you're doing [expletive] WHAT with user DMs, messages, files, etc? I'm positive I'm not reading this correctly." Attached is a screenshot of Slack's opt-out instructions for their machine learning models. Slack (@SlackHQ) responded: "Hello from Slack! To clarify, Slack has platform-level machine-learning models for things like channel and emoji recommendations and search results. And yes, customers can exclude their data from helping train those (non-generative) ML models. Customer data belongs to the customer. We do not build or train these models in such a way that they could learn, memorize, or be able to reproduce some part of customer data. Our privacy principles applicable to search, learning, and AI are available here: [link]." Another response from Slack (@SlackHQ) on May 17: "Slack AI – which is our generative AI experience natively built in Slack – is a separately purchased add-on that uses Large Language Models (LLMs) but does not train those LLMs on customer data. Because Slack AI hosts the models on its own infrastructure, your data remains in [link]."
Corey Quinn denounces Slack’s opt-out policy to train machine learning model
Quinn was referencing an excerpt from Slack’s Privacy Principles, which states, “To develop AI/ML models, our systems analyze Customer Data (e.g. messages, content, and files) submitted to Slack as well as Other Information (including usage information) as defined in our Privacy Policy and in your customer agreement.”

Another extract reads: “To opt out, please have your org, workspace owners or primary owner contact our Customer Experience team at [email protected].”

Slack quickly responded to the post, confirming that it is using customer content to train certain AI tools in the app. However, they clarified that this data is not used for their premium AI offering, which they state is completely separate from user information.

The cloud-based team communication platform also told TechRadar Pro that the information it uses to power its ML is anonymized and does not access messages.

The president of the end-to-end encrypted messaging app Signal, Meredith Whittaker, criticized Slack for using the data. She said on X: “Signal will never do this. We don’t collect your data in the first place, so we don’t have anything to ‘mine’ for ‘AI’.”

Slack responds to criticism over use of user data to train models

In response to the community uproar, the Salesforce-owned company posted a separate blog addressing the concerns, stating: “We do not build or train these models in such a way that they could learn, memorize, or be able to reproduce any customer data of any kind.”

Slack also confirmed that user data is not shared with third-party LLM providers for training purposes.

 (Threads Post by Slack Engineer):aaronjmaurer posted 4 days ago: "We do need to update this particular page to explain more carefully how these privacy principles play with Slack AI. It was originally written about the search/recommendation work we've been doing for years prior to Slack AI. However, in all the Slack AI material we are extremely clear, as I linked: 'Slack does not share customer data with LLM providers and does not use customer data to train large language models (LLMs).'"
A Slack engineer tries to clarify the company’s position, claiming user data had been used “for years prior to Slack AI”

A Slack engineer attempted to clarify the situation on Threads, explaining that the privacy rules were “originally written about the search/recommendation work we’ve been doing for years prior to Slack AI,” and admitting that they do “need an update.”

Featured image: Canva

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Suswati Basu
Tech journalist

Suswati Basu is a multilingual, award-winning editor and the founder of the intersectional literature channel, How To Be Books. She was shortlisted for the Guardian Mary Stott Prize and longlisted for the Guardian International Development Journalism Award. With 18 years of experience in the media industry, Suswati has held significant roles such as head of audience and deputy editor for NationalWorld news, digital editor for Channel 4 News and ITV News. She has also contributed to the Guardian and received training at the BBC As an audience, trends, and SEO specialist, she has participated in panel events alongside Google. Her…

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