Open cards and API Request meaning.
Asked by arjay:

Good day! Can you help me to understand those limitations and naming.  

1. What are open cards / open lists?  
2. Attachments per API Request.  
3. Board - per members API Request.  
4. Action - Total per move (If i move 1 list with 3 cards, does it count 1 move?)  
5. Emaile2bperHour  
6. Boards - per member API Request  
7. Cards - With actions per API Request  
8. Boards - Total access request per board  
9. What is the difference between attachment per API Request and attachment per board? I am a little bit confused because they both have 36,000.  

Thank You!


Answers:
author: Mutya A
body: Hi arjay, welcome to the Community!

Sounds like you are referring to our Trello resource limits page: <https://trello.com/1/resource/limits>

I would highly recommend to explore our API [Introduction](https://developer.atlassian.com/cloud/trello/guides/rest-api/api-introduction/) and [Reference](https://developer.atlassian.com/cloud/trello/rest) documentation if you'd like to know more about our API requests. You can also have a look at the [Trello Help](https://help.trello.com/) page for some basic concepts on all things Trello in general. I am also interested to know what your use case is so we can provide you a much better explanation. For now I'll try to answer your questions to the best of my knowledge :)

1. Open cards or lists are any cards or lists you see on your boards that are active, and not deleted.
2. There is also a limit of 36,000 attachments you can retrieve per API request.
3. Are you referring to the "perMembersApiRequest" in boards?
4. [Actions](https://developer.atlassian.com/cloud/trello/guides/rest-api/api-introduction/#actions) contain each of the actions that have been taken on a Card or Board or members of a Card. Comments are also stored as a special type of Action on a card. Here are samples of the [Action Types](https://developer.atlassian.com/cloud/trello/guides/rest-api/action-types/). I am seeing two Action Types for lists that might be relevant for moving 1 list so I am assuming that it only counts as one move depending which of these you will use:
   1. moveListFromBoard
   2. moveListToBoard
5. This is the [email-to-board](https://support.atlassian.com/trello/docs/creating-cards-by-email/) feature that we have. That means we have a limit of # of emails sent per hour.
6. Can you explain more what the difference is with the #3 question?
7. Maximum number of actions you can retrieve per card per API request. Here are the list of some [card-level actions](https://developer.atlassian.com/cloud/trello/guides/rest-api/nested-resources/#nested-cards-as-url-params).
8. I'm just assuming that it's maximum number of users getting access/invite requests per board.
9. There is a limit of 36,000 attachments you can upload for each board. There is also a limit of 36,000 attachments you can retrieve per API request.

If this helps, this is a documentation about number of objects (cards, checklists, stickers, etc.) that can exist on a board or card: <https://developer.atlassian.com/cloud/trello/guides/rest-api/limits/>

This would be really great questions to share in our developer community. We have a number of Trello Engineers that are active there, and they'd be happy to give some guidance for more advanced topics like these.

<https://community>.developer.atlassian.com/c/trello

Hope this helps!