Slack search powers visibility and compliance across your organisation

With Slack search and Agentforce, the information that you need is always at your fingertips.

By the team at Slack17th December 2024

Slack search allows teammates to find the answers that they need quickly, across messages and files, and within a variety of organisational and compliance boundaries. Slack’s search index is designed to respect the complex visibility and compliance requirements of Slack’s multi-channel, multi-organisational ecosystem while delivering the fast, accurate, insightful results that users expect.

This is even more relevant in an agentic era. With Agentforce, autonomous AI agents can tap into permission-aware information in Slack, empowering Agentforce to continuously learn and provide smarter responses. When teammates – human or AI – can easily and securely access your company’s knowledge base so that you can work smarter, faster and more productively.

Learn how Slack’s search system supports message and file visibility, adapts to external compliance and security standards, and scales to connect a global workforce in the agentic era.

Messages: Granular visibility by design

Slack channels come in many flavours – public, private, shared and even multi-workspace – each with specific visibility requirements. Our search system ensures that a message is visible only to the right users by indexing messages based on their respective channel types and applying visibility filters at the time of the query. This means that teammates can only see search results from messages that they can access.

Channel-based visibility

Messages inherit their visibility from the channel that they belong to. Channels may have unique rules:

  • Public channels (non-shared): Visible to all workspace members. These are indexed with the workspace ID and filtered at query time using the user’s workspace memberships.
  • Private channels: Visible only to channel members. Private channel memberships are queried directly to avoid listing every member ID in the index.
  • Org-shared public channels: Visibility depends on whether a channel is shared across workspaces (cross-workspace or organisation-wide). Index updates are deferred to offline jobs, while real-time queries dynamically adjust for recent changes in workspace sharing.
  • Direct messages (DMs) and multi-person direct messages (MPDMs): Membership lists are small and static, so messages are indexed with member IDs.

Externally shared channels

When a channel is shared across organisations with Slack Connect, each participating external partner gets its own indexed copy of the message. This maintains compliance with the visibility rules of the respective organisation, no matter how the channel is classified.

Files: Visibility through sharing

Files in Slack follow a similar visibility model, determined by the channels/DMs/MPDMs that they’re shared in. Our search index represents file shares as 'child' documents, enabling us to express complex visibility rules at query time.

Key indexing patterns for files

  • Files shared in public channels are indexed by the workspace ID of the channel.
  • Files in private channels are restricted by channel membership.
  • Org-shared channels use workspace or organisation IDs, with dynamic query adjustments for recent sharing changes.
  • Files shared in DMs or MPDMs are indexed with member IDs of all involved users.

The use of child documents allows us to efficiently handle files shared across multiple channels without duplicating data in the index.

Agentforce: Smarter AI, powered by Slack search

Slack’s search functionality is enhanced by intelligent systems such as Agentforce, which leverages retrieval-augmented generation (RAG) techniques. These systems analyse and retrieve data within authorised channels in real time, delivering precise and context-aware results. With relevant information at their fingertips, teams are empowered to make decisions faster than ever.

How it works

  • On-demand search: When users query Agentforce, the system automatically determines whether to invoke the Slack search action. If needed, this action retrieves search results from Slack, including messages and files within the user’s approved context.
  • Contextual results: Agentforce retrieves only the content visible to the user making the query – whether messages, files or other workspace data.
  • Real-time insights: Results are based on the user’s current context, ensuring that responses are fresh, relevant and actionable.

Security and privacy first

We’ve designed the Slack search actions to prioritise trust and safety:

  • Visibility-based access: Agentforce can retrieve only content that the user can already see, ensuring no unintended data exposure.
  • Admin controls: Workspace admins have full control over enabling and configuring the Slack search action for their teams.
  • Minimised data sharing: Data remains within Slack’s secure ecosystem, avoiding unnecessary duplication or external transfers. By keeping data in one place, we can instantly follow any changes, like making a channel private or removing teammates from channels.

By maintaining these safeguards, Agentforce delivers powerful AI-driven experiences without compromising user privacy or workspace security.

Compliance: Balancing visibility, security and control

Slack is designed to give organisations the visibility that they need for collaboration while meeting stringent compliance requirements. This makes Slack a trusted platform for highly regulated industries, guaranteeing data security and adherence to international standards.

FedRAMP certification

Slack supports both FedRAMP Moderate and FedRAMP High environments. FedRAMP High environments are supported by GovSlack, a separate isolated environment running in AWS GovCloud. While both of these environments have powerful search capabilities, this isolation guarantees that information isn’t searchable or shared across environments.

Enterprise Key Management

Enterprise Key Management enhances data security by allowing organisations to manage their own encryption keys through a third-party key management service. Messages and files are encrypted and decrypted in real time, providing seamless collaboration while maintaining control over access. Keys can be rotated or revoked to meet compliance and regulatory requirements.

International data residency

Slack supports customers with region-specific data residency needs by hosting search clusters in multiple geographic regions. This guarantees that data remains within its designated region, meeting local regulatory and compliance standards.

Custom retention policies

Organisations can define retention policies for messages and files, making sure that data is kept only for the required duration. Slack enforces these policies by regularly purging expired data from its database and search index, providing both flexibility and compliance with data governance needs.

Scaling for the future

Whether it’s handling dynamic channel sharing, ensuring compliance with complex standards or scaling to meet the needs of large organisations, Slack’s engineering team continues to innovate to ensure that search remains fast, reliable and secure.

Talk with an expert to learn more about this exciting intersection of distributed systems, search technology and security.

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