You can use the free version of Slack for as long as you'd like, and there's no limit to the number of members who can be invited, but there are a few usage limits to consider:

• Message and file visibility
  View and search messages and files from the last 90 days.
• Data retention
  Use data retention to automatically delete messages and files older than 90 days.
• Apps
  Install up to 10 third-party or custom apps.

Tip: Upgrading to a paid plan will remove message and app limits, provide more data retention options, and increase your workspace's file storage limit.

 

Message and file visibility limit

On the free version of Slack, people can view and search messages and files in their workspace from the last 90 days. Files include things like clips, PDFs, documents, images, screenshots, audio and video files. Keep in mind that you'll only be able to see messages in public channels, private channels you belong to, and your direct messages when searching. 

When your workspace reaches the visibility limit of the free plan, Slack will start hiding messages and files older than 90 days to make room for new ones. If you upgrade your workspace to a paid plan, you'll unlock access to your entire message and file history. 

 

Data retention

Workspace Owners on the free plan can use basic data retention settings to delete messages and files after 90 days. Applying basic data retention settings allow you to automatically delete messages and files that are hidden by the free plan.

App installation limit

Members of workspaces on the free version of Slack can add up to 10 apps. Apps from the Slack App Directory and custom apps built for your team count towards this limit. 

If your workspace reaches the app and integration limit, you can uninstall apps to make space for new ones, or upgrade to a paid plan to install as many apps as you'd like.