As someone who has developed several #ActivityPub software implementations (Fedify, Hollo, BotKit, and Hackers' Pub), I believe one of the most frustrating features to implement in the #fediverse is #custom_emoji.

The challenges are numerous:

First, there's no standardization. ActivityPub specifications don't define how custom emoji should work, leading to inconsistent implementations across different servers like Mastodon and Misskey.

Rendering is particularly problematic. Emojis must display properly across different contexts (in text, as reactions, in emoji pickers) while maintaining quality at various sizes. Animated emojis add another layer of complexity.

Perhaps most concerning is the poor #accessibility. Most implementations simply use the emoji code (like :party_blob:) as the alt text, which provides no meaningful information to screen reader users (in particular, non-English speakers) about what the emoji actually depicts or means.

What really dampens my motivation to implement this feature is knowing I'm investing significant effort into something that ultimately creates accessibility barriers. It's disheartening to work hard on a feature that excludes part of the community.

#fedidev

@hongminhee I know there's a FEP for emoji reactions, but I don't think there's ever been one for custom emojis? https://codeberg.org/fediverse/fep/src/branch/main/fep/c0e0/fep-c0e0.md

@hongminhee I plan to write a FEP documenting existing implementations (it is needed to finalize my emoji reactions FEP).

>Most implementations simply use the emoji code (like :party_blob:) as the alt text, which provides no meaningful information to screen reader users

Do you know implementations that provide alt text for custom emojis?

@silverpill@mitra.social I personally didn't find integrating custom emoji to be difficult at all.

However NodeBB did already have custom emoji support (so it was fairly straightforward to add the outbound federation support), and as for inbound, the short code is defined in the payload and a simple regex replace handles it ok.

Sure, some emoji might look weird if they have different aspect ratios, but that's something outside the scope of what I'd want. All remote emoji are reduced down to a small square (or technically I think it's maybe max width and height of 1rem or similar), inline with the text and that honestly works with like 99% of the emoji I see.

cc @hongminhee@hollo.social

Another annoying thing about the current custom emoji spec in the fediverse: the type is just called Emoji instead of CustomEmoji. Such a small detail, but it creates unnecessary ambiguity between Unicode emojis and custom ones. I ran into this while implementing BotKit and had type name collisions with Emoji—had to use awkward namespacing to work around it. These little inconsistencies make implementation more tedious than it needs to be.

@julian @hongminhee

Started writing it

feps/9098/fep-9098.md at main

feps - My FEPs

Codeberg.org (codeberg.org)

Listed requirements for the Emoji object.
I should probably describe the microsynax there as well, and how custom emojis are rendered.

@silverpill @julian @hongminhee you have listed "Image is a square" but is definitely not true for Misskey. And Mastodon renders Misskeys long emojos just fine.
Actually mastodon does fine with long emojos now too

@silverpill @julian @hongminhee you have listed "Image is a square" but is definitely not true for Misskey. And Mastodon renders Misskeys long emojos just fine.
Actually mastodon does fine with long emojos now too

@thisismissem@hachyderm.io You're right, I don't believe there's a specific FEP for custom emojis yet. If one were to be created, accessibility through proper alt text would definitely need to be a core requirement. The current state where emoji codes like :blob_wave: become the alt text creates significant barriers for screen reader users—especially for non-English speakers, who face an additional language barrier when trying to understand these codes. A proper standard should address how to provide meaningful descriptions that actually convey what the emoji represents in multiple languages.

@hongminhee @thisismissem

I think we can use summary property on Emoji object. It's one of those properties for which the spec allows multi-language mappings:

Activity Vocabulary

(www.w3.org)

@silverpill @hongminhee @thisismissem

`summary` could represent *some* kind of accessible information, but it's not obvious to me which kind exactly: should it be an accessible name (<https://developer.mozilla.org/en-US/docs/Glossary/Accessible_name>) or an accessible description (<https://developer.mozilla.org/en-US/docs/Glossary/Accessible_description>)? (Or even an HTML `title` attribute?)

(I think it's unfortunate that we need to reinvent an accessibility tree representation, when an AS2 `content` is just an HTML, which has already been equipped with a feature-rich and battle-tested accessibility framework called ARIA, but I digress.)

@liaizon @julian @hongminhee

Requirements in that section are meant for those who want maximum compatibility. For example, JPEGs and images larger than 256 KB are supported by Pleroma and others, but Mastodon doesn't allow them.

Non-square emojis are a bit more complicated. They are not rejected by most servers, but might not be displayed properly by clients.

I just visited your instance and made a screenshot of how emoji is rendered by web UI (attached). The emoji is present, but I can't tell what is depicted there. Some clients enlarge custom emojis on hover, but not Mastodon, so I have to open the image in a new browser tab, or zoom in the page. This is no ideal, hence the recommendation in the FEP.

@hongminhee
Fedibird seems to have a feature that lets you see details about emojis, which may also contribute to accessibility.
https://fedibird.com/@noellabo/113876564190790916

@hongminhee @silverpill @ozoramore @julian @liaizon @tesaguri

(This is in Japanese. Please use machine translation.)

カスタム絵文字については以前から問題意識があって、Fedibirdの実装を通じて解決策を模索してきました。

FEPを検討しているなら、ぜひ拾い上げてください。ひとまず概要を。

・スクエアではない絵文字の取り扱い

・アクセシビリティと多言語対応

・コピー許可と権利情報

・センシティブの扱い

・画像形式やサイズ、アニメーションの互換性やガイドライン

以下は、カスタム絵文字に付与可能な属性をできるだけ記載したサンプルです。

添付画像は、画像化されたテキストを中心とする絵文字に対し、代替テキストが設定され、ツールチップ表示されているサンプルです。

この絵文字のObject表現（JSON）はこちら。
https://fedibird.com/emojis/prohibits_importing_to_other_servers_ja.json

人間向けの公開ページはこちら。
https://fedibird.com/emojis/prohibits_importing_to_other_servers_ja

Fedibirdのcustom_emojis APIのエンティティ
https://fedibird.com/api/v1/custom_emojis/prohibits_importing_to_other_servers_ja

@hongminhee @silverpill @ozoramore @julian @liaizon @tesaguri When reconsidering the specifications of custom emoji, it would be a good idea to also take into account the information provided by emojis defined in Unicode.

Unicode emojis provide a string that describes what kind of image is depicted, as well as a translation string, so I think it would be better to use them while taking compatibility and consistency into consideration.

@hongminhee @silverpill @ozoramore @julian @liaizon @tesaguri For non-square custom emojis, you should provide width and height in the API response (entity).

This will help client app developers recognize and support non-square emojis.

This is actually very useful, as it improves the user experience by allowing efficient layout before fetching the image.

This may not be necessary for ActivityPub S2S, but it may be useful if you have a case where you can use a dummy image as a placeholder when you can't handle the emoji image.

@hongminhee @silverpill @ozoramore @julian @liaizon @tesaguri @thisismissem Fedibird currently provides the following information to help users understand the content of custom emojis:

- alternateName (alternate_name)

- ruby

- description

alternateName is not a shortcode that serves as a handle, but an alternative expression or name for the emoji content in text.

ruby is equivalent to the ruby ​​element in HTML. It is also useful as an index when selecting a custom emoji from a picker, especially in CJKV.