DevTools extensions are developer tools provided by third-party packages that are tightly integrated into the DevTools tooling suite. Extensions are distributed as part of a pub package, and they are dynamically loaded into DevTools when a user is debugging their app.

If your app depends on a package that provides a DevTools extension, the extension automatically shows up in a new tab when you open DevTools.

You need to manually enable the extension before it loads for the first time. Make sure the extension is provided by a source you trust before enabling it.

When you open the extension for the first time, you'll see a prompt to enable the extension:

You can modify the setting at any time from the DevTools Extensions dialog:

Note: if the extension requires a running a connection to a running application, you will not see the enablement prompt or enablement settings until DevTools is connected to a running app.

Extension enablement states are stored in a devtools_options.yaml file in the root of the user's project (similar to analysis_options.yaml).

description: This file stores settings for Dart & Flutter DevTools.
documentation: https://docs.flutter.dev/tools/devtools/extensions#configure-extension-enablement-states
extensions:
  - provider: true
  - shared_preferences: true
  - foo: false

This file stores per-project (or optionally, per user) settings for DevTools.

If this file is checked into source control, the specified options are configured for the project. This means that anyone who pulls a project's source code and works on the project uses the same settings.

If this file is omitted from source control, for example by adding devtools_options.yaml as an entry in the .gitignore file, then the specified options are configured separately for each user. Since each user or contributor to the project uses a local copy of the devtools_options.yaml file in this case, the specified options might differ between project contributors.

For an in-depth guide on how to build a DevTools extension, check out Dart and Flutter DevTools extensions, a free article on Medium.

To learn more about writing and using DevTools extensions, check out the following video:

Watch on YouTube in a new tab: "Building DevTools extensions | Flutter Build Show"