Getting Started

Introduction

Trello provides a simple RESTful web API where each type of resource (e.g. a card, a board, or a member) has a URI that you can interact with.

For example, if you’d like to use the API to get information about the Trello Development board, you’d use the following URI:

https://api.trello.com/1/boards/4d5ea62fd76aa1136000000c

Notes:

  • All API requests go to https://api.trello.com
  • The /1 part of the URI is the API version
  • The /boards part means that we’re addressing Trello’s collection of boards
  • The /4d5ea62fd76aa1136000000c part is the id of the board that we want to interact with. You’ll notice that the board id is also part of the board’s URL in Trello

The simplest thing you can do with a Trello resource URI is GET it. (When using REST API via HTTP, you “read” something by using the HTTP GET method).

However, if you GET the aforementioned URI (https://api.trello.com/1/boards/4d5ea62fd76aa1136000000c), for example by pasting it in the address bar of a web browser, you won’t get the board data; instead you’ll get an invalid key error (with a 401 Unauthorized HTTP status code). That’s because all requests to the Trello API must include an application key, which Trello uses to identify the application making the request.

Getting an Application Key

You can get your application key by logging into Trello, and then visiting https://trello.com/1/appKey/generate

Your 32-character application key will be listed in the first box. For the rest of the examples, we’re going to assume that your application key is substitutewithyourapplicationkey

If you’re doing a GET request, you include your application in the query string portion of the URL. If you GET https://api.trello.com/1/board/4d5ea62fd76aa1136000000c?key=substitutewithyourapplicationkey you’ll no longer get an error. Instead, you’ll get a response that looks like this:

{"id":"4d5ea62fd76aa1136000000c","name":"Trello Development","desc":"Trello board used by the Trello team to track work on Trello.  How meta!\n\nThe development of the Trello API is being tracked at https://trello.com/api\n\nThe development of Trello Mobile applications is being tracked at https://trello.com/mobile","closed":false,"idOrganization":"4e1452614e4b8698470000e0","url":"https://trello.com/board/trello-development/4d5ea62fd76aa1136000000c","prefs":{"voting":"public","permissionLevel":"public","invitations":"members","comments":"public"}}

All the responses to Trello API calls use JSON. You can make the response look prettier by running it through a javascript beautifier, which will give you something like this:

{
    "id": "4d5ea62fd76aa1136000000c",
    "name": "Trello Development",
    "desc": "Trello board used by the Trello team to track work on Trello.  How meta!\n\nThe development of the Trello API is being tracked at https://trello.com/api\n\nThe development of Trello Mobile applications is being tracked at https://trello.com/mobile",
    "closed": false,
    "idOrganization": "4e1452614e4b8698470000e0",
    "url": "https://trello.com/board/trello-development/4d5ea62fd76aa1136000000c",
    "prefs": {
        "voting": "public",
        "permissionLevel": "public",
        "invitations": "members",
        "comments": "public"
    }
}

If you wanted to include additional information in the response, you could add additional parameters (documented here). For example, if you wanted to also get all the open lists and cards on the Trello Development board, you could GET this URL:

https://api.trello.com/1/board/4d5ea62fd76aa1136000000c?key=substitutewithyourapplicationkey&cards=open&lists=open

If you wanted to read a board of your own, you could get its id (the easiest way is to visit the board in Trello and copy the id out of the URL), and request

https://api.trello.com/1/board/substitutewiththeboardid?key=substitutewithyourapplicationkey

However, unless your board is public (like the Trello Development board), when you try to GET that URL, you’ll get a 401 unauthorized error. You can only read a private board (or card, or organization) if the API knows that you have permission to read that resource. You can tell the API that you’ve been authorized to read private data by including a token, which is given to your by a user and which allows you to read (and potentially write) things on their behalf.

Notes:

  • The application key is used only to let Trello know which application is making the request; it doesn’t tell Trello who the request is being made on behalf of. For example, if you’re using your own application key, you still need to generate a token to be able to access any of your private boards.

Getting a Token from a User

Full documentation for authorizing a client can be found at Authorizing a Client, and for authorizing via OAuth can be found at Authorizing via OAuth.

You can request a token from a user by directing them to an authorization URL, like the following:

Request a token granting read-only access for 30 days (the default):

https://trello.com/1/authorize?key=substitutewithyourapplicationkey&name=My+Application&expiration=30days&response_type=token

Request a token granting read-only access forever:

https://trello.com/1/authorize?key=substitutewithyourapplicationkey&name=My+Application&expiration=never&response_type=token

Request a token granting read/write access for 1 day:

https://trello.com/1/authorize?key=substitutewithyourapplicationkey&name=My+Application&expiration=1day&response_type=token&scope=read,write

If the user accepts your request, they’ll be directed to a page where they will be given a token (64 characters), which they can give back to your application. If you add the token to your request, like so:

https://api.trello.com/1/board/substitutewiththeboardid?key=substitutewithyourapplicationkey&token=substitutethispartwiththeauthorizationtokenthatyougotfromtheuser

... then you’ll be able to read a board that’s only visible to the user

Once you’ve gotten a token from a user, you can also make requests that give you information about the user that authorized the token, like this:

Get the member’s record:

https://trello.com/1/members/me?key=substitutewithyourapplicationkey&token=substitutethispartwiththeauthorizationtokenthatyougotfromtheuser

Get the cards that a user is assigned to:

https://trello.com/1/members/my/cards?key=substitutewithyourapplicationkey&token=substitutethispartwiththeauthorizationtokenthatyougotfromtheuser

Get the open boards that a user is a member of:

https://trello.com/1/members/my/boards?key=substitutewithyourapplicationkey&token=substitutethispartwiththeauthorizationtokenthatyougotfromtheuser

Get the boards that a user has pinned to their boards menu:

https://trello.com/1/members/my/boards/pinned?key=substitutewithyourapplicationkey&token=substitutethispartwiththeauthorizationtokenthatyougotfromtheuser

Get the organizations that a user is a member of:

https://trello.com/1/members/my/organizations?key=substitutewithyourapplicationkey&token=substitutethispartwiththeauthorizationtokenthatyougotfromtheuser

Of course, having a user copy and paste a token into your application isn’t very pretty. The Trello API also supports basic OAuth; you can use an OAuth library and the following URLs:

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/1/appKey/generate.

Using client.js

If you’re developing an application that has a web interface, you can use the Trello API client library, like so:

<head>
  <!-- ...  -->

  <!-- The client library requires jQuery  -->
  <script src="http://code.jquery.com/jquery-1.7.1.min.js"></script>
  <script src="https://api.trello.com/1/client.js?key=substitutewithyourapplicationkey"></script>

  <!-- ...  -->
</head>

The un-minified, documented source of client.js is at https://trello.com/1/client.coffee

Documentation for using client.js is at client.js

The client library can take care of getting the authorization token from the user, and provides a wrapper around the GET, PUT, POST and DELETE HTTP methods.

Examples using the client library:

Watching Models with Webhooks

Webhooks provide a way for third party applications to keep Trello data in sync with their own servers. Webhooks can be registered to watch models, and when a change happens on one of those models, the third party is informed.

Full documentation on Webhooks can be found at Webhooks.