Authorizing With Trello's REST API

Introduction

Trello's API uses token-based authentication to grant third-party applications access to the Trello API. Once a Trello user has granted an application access to their Trello account and data, the application is given a token that can be used to make requests to the Trello API on behalf of the user.

There are two ways to authorize a client and receive a User Token. The first is via our authorize route, the second is via basic OAuth1.0. We'll cover the former now. If you'd rather use OAuth, you can skip ahead to Using Basic OAuth.

Authorizing a client

To begin the authentication process, you need an API key. Every Trello user is given an API key. You can retrieve your API key by logging into Trello and visiting https://trello.com/app-key/.

Because the API key is tied to the user, it is often a good idea to create a Trello user specifically for building a single application or integration. This ensures that a third-party's integration is disassociated from a third-party integration's developer's Trello account.

Once you have an API key, you will use it to ask a Trello user to grant access to your application. To do so, you should direct a user to the authorize URL and pass along the query parameters needed as documented below. The authorize prompt can be opened in a number of different ways and with a number of different options.

When you kick off the authorization flow, the user will see the following screen:

The name of the application, length of access, and scope of permissions are all configurable via query params (documented below).

For instance, if you're just getting started with Trello's API and you'd like to explore what is possible, you can generate a token for yourself using your API key and the following URL: https://trello.com/1/authorize?expiration=1day&name=MyPersonalToken&scope=read&response_type=token&key={YourAPIKey}

After visiting this page and clicking the green Allow button, you'll be redirected to a page with your token. You can now use that token and your API key to make a request to the Trello API. You can give it a try with: https://api.trello.com/1/members/me/?key={yourAPIKey}&token={yourAPIToken}. This should return an object containing information about your Trello user.

If you’re authorizing a web client, you may want to check out client.js, a wrapper for the API in javascript. It includes built-in authorization methods that you may find useful. However, it uses the same route as is documented below.

1/authorize/ Route Options

Handling User Deny

Depending on the response_type you are using, Trello will do one of two things when a user clicks "Deny" from the authorization flow's prompt.

Revoking Tokens

Trello users can view metadata regarding the applications they have authorized and granted a token by visiting their account settings page: https://trello.com/{username}/account. There, under the Applications heading, they will see a list of every application they've granted access to, the scope of the access, the date access was approved, and the date that the token expires.

Users are able to revoke a token by clicking on the Revoke button next to the listing. Revoking the token removes the token's access to the user's account and it can no longer be used to make requests to Trello's API on behalf of the user.

Tokens can also be deleted via the API. There is a /1/tokens resource that includes a DELETE action.

Applications and Power-Ups should handle token revocation gracefully. If a token has been revoked, the API will respond with a 401 HTTP status and the message: invalid token. At that point in time, the Power-Up or integration should ask the user to re-authorize the application.

Allowed Origins

When your application is authenticating a user, you may provide a return_url that Trello will redirect to after the user gives consent for your application. By default an application key can redirect to any domain, but we strongly recommend that you specify the origins that your application will redirect to when completing authorization.

For example, if we were GitHub building a GitHub integration for Trello, and we know we will only ever redirect back to https://github.com after the user grants access in the auth flow, or perhaps also http://localhost:3000 for local development, we could add both of those as allowed origins for our application, and no one will be able to use our API key to authenticate users and pass back the token to any other URLs, like https://bad.example.com.

You can view and edit your application's allowed origins at: https://trello.com/app-key.

Note: If your API key has no allowed origins set, then no redirect URL will work. By default, all API keys will have a wildcard * allowed origin which permits any URL to be used.

Using Basic OAuth

The Trello API supports basic OAuth 1.0; you can use an OAuth library and the following URLs:

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https://trello.com/1/OAuthGetRequestToken
https://trello.com/1/OAuthAuthorizeToken
https://trello.com/1/OAuthGetAccessToken

You’ll also need your application secret (used to sign your requests). That’s listed in the second box on https://trello.com/app-key.

Example OAuth Project In Node.js

We've put together an example project in node that demonstrates the basic routes and configuration necessary to use OAuth to access Trello's API. You can view the Glitch project here.