You're reading this because you're looking for info on legacy custom integrations: an outdated way for teams to integrate with Slack. These integrations lack newer features and will be deprecated and possibly removed in the future. We do not recommend their use.
Instead, we suggest that you read about their replacement: Slack apps. Slack apps can be built just for your own workspace or distributed through the App Directory, and they can use the latest and greatest APIs and UI features.

Legacy: Web API

The Slack Web API is an interface for querying information from and enacting change in a Slack workspace.

Because we strongly recommend you do not use legacy custom integrations anymore, you should instead use the Web API with Slack apps. Our guide to the Web API will walk you through the process of using it in a Slack app.

Migrating from legacy tokens

If you were using a legacy token to make calls with the Web API, you'll need to generate a new one for your modern Slack app. If you chose to build a workspace app, you can install it to your own workspace in a couple of clicks. Then prepare it for distribution by following our guide to using OAuth to generate workspace tokens. Traditional Slack apps can follow our guide to the OAuth flow.

For testing and development, you can quickly and easily create a new workspace app and install it in two clicks - just follow our Getting Started guide.

Once it's installed, use the app's settings to progressively add the permission scopes you need for your testing.