How connecting two apps works and what data you share when authorising it

The short answer: connecting two applications does not mean handing over your password or granting full access to your account. In practice, you authorise one service to request specific data from another via a temporary digital key that you can revoke at any time.

From passwords to access tokens

When you click the button to link a service—for example, when adding your email or task manager to a unified dashboard—you are not typing your password into the destination app. The standard method across the internet relies on a secure authorisation protocol (usually OAuth).

In this flow, the provider where you already hold an account (such as Google, Microsoft, Apple, or Todoist) displays its own screen to ask for confirmation. If you accept, that provider issues an encrypted credential known as a token and hands it to the requesting application. This digital key has a specific expiry date, works exclusively for that tool, and allows information to be accessed without ever exposing your login credentials.

Scopes: what each service can and cannot see

Each connection defines a specific list of permissions, known technically as scopes. A well-designed tool should only ever request what is strictly necessary to fulfil its purpose.

It is worth distinguishing between two common levels of permission:

• Read-only access: the third-party app can only view and display items (for instance, reading calendar events or pending tasks to show them on screen), without being able to create new appointments, edit notes, or delete records.
• Read and write access: the application can alter your data, create events, mark tasks as completed, or archive emails on your behalf.

Before confirming any connection, the consent screen sets out precisely which areas the app is requesting access to: basic profile, calendar, contacts, or messages. If a service whose sole purpose is to view your calendar asks for permission to send emails or browse your cloud files, it is worth pausing to consider whether that integration makes sense. In our section on integrations, we explore in greater detail how these tools interact.

How data travels and where it is processed

When considering how to organise email, calendar and tasks in one place, a common question arises: does your data remain solely on your device, or does it pass through intermediary servers? The answer depends on the architecture of each tool:

• Direct local connection: the app installed on your phone or computer communicates directly with the provider via its official interface (API) and stores data in the device's local memory.
• Server-side synchronisation: the service's servers communicate with those of your providers, bring the information together, and return it to you in a structured format. This enables features that require background processing, such as generating daily summaries or triggering alerts even when your device is switched off.

In this latter scenario, storage guarantees become particularly crucial. Under the GDPR framework, every service must clearly state in its privacy policy what data it retains, for what purpose, for how long, and in which physical jurisdiction its servers—or those of any third-party processors it relies upon—are located.

How to audit and revoke access when you no longer need it

One of the greatest advantages of the token system is that control remains firmly in your hands. The authorisation granted is neither irreversible nor indefinite.

If you stop using an app or decide that two platforms should no longer communicate, you do not need to uninstall software to cut off the data flow. You simply need to go to your main account's security dashboard (under the section for third-party apps or connected accounts) and revoke permission with a single click. At that very moment, the token is permanently invalidated, and the connected app loses all ability to query further information.