# Certification v2 Questions

**URL:** <https://forum.dfinity.org/t/certification-v2-questions/23775>\
**Category:** Language Support\
**Tags:** Motoko\
**Created:** [October 15, 2023, 9:42pm UTC](https://forum.dfinity.org/t/certification-v2-questions/23775 "2023-10-15T21:42:25Z")\
**Posts on this page:** 1\
**Showing post:** 3

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**Author:** ![skilesare](https://sea1.discourse-cdn.com/flex023/user_avatar/forum.dfinity.org/skilesare/32/5609_2.png) [@skilesare](https://forum.dfinity.org/u/skilesare)\
**Post date:** [October 15, 2023, 11:59pm UTC](https://forum.dfinity.org/t/certification-v2-questions/23775/3 "2023-10-15T23:59:24Z")

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> [@NathanosDev](#):
>
> Yes, but if you’re only certifying headers that affect browser behavior then you should know these ahead of time anyway. Things like CORS, caching (incl ETAG), content-encoding, and content type. Are there any scenarios that you’re concerned about deciding these headers ahead of time?

My biggest concern is future compatibility and needing to somehow re-calculate the entire tree of certifications if there’s some new header that needs to be added. Are NFT has a number of importance of expose the info with every NFT in the collection. These are generally exposed to Jason files so that’s easy to query and get all the info about a particular Nft. We also allow multi library to be put into each nft at each of that is certified as well. I’m just trying to think about how we would even convey to a user who’s trying to upload their library. What they need to do about this. We want it to be extensible and allow the user to decide, but it’s one thing to know you want to upload three pictures, it’s another to have to think about how long you want them cached for.

> [@NathanosDev](#):
>
> that doesn’t need to be stored, only the [hash of the whole response](https://internetcomputer.org/docs/current/references/http-gateway-protocol-spec#response-hash-calculation).

I guess this answers my question. Looks like we’re going to have to have some kind of structure that looks like an HTTP response and that will be encoded somehow? We take the hash of the whole thing and store that? Does it still go in a particular sub tree of the canister certification?

Very helpful responses all around. I’ll reach out directly and maybe we can work through it and figure out a path to get motoko working.

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