# HEEx - syntax reference and engine extension points

**URL:** <https://forum.elixirforum.com/t/heex-syntax-reference-and-engine-extension-points/46677>\
**Category:** Questions\
**Tags:** heex\
**Created:** [March 18, 2022, 5:52pm UTC](https://forum.elixirforum.com/t/heex-syntax-reference-and-engine-extension-points/46677 "2022-03-18T17:52:47Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![tmbb](https://forum.elixirforum.com/letter_avatar_proxy/v4/letter/t/77aa72/32.png) [@tmbb](https://forum.elixirforum.com/u/tmbb)\
**Post date:** [March 18, 2022, 5:52pm UTC](https://forum.elixirforum.com/t/heex-syntax-reference-and-engine-extension-points/46677/1 "2022-03-18T17:52:47Z")

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I’ve been out of the loop for the whole HEEx thing, despite experimenting a lot with EEx rendering optimizations.

I have some HEEx questions I haven’t found answered anywhere:

1. Is there a syntax reference for HEEx somewhere? I’m not sure what exactly is valid HEEx

2. Is there a well-defined API for custom HEEx engines? I’d love to experiment on HTML rendering optimizations based on HEEx just like I’ve done for EEx, but I’m not sure that’s even meant to be possible

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**Author:** ![chrismccord](https://forum.elixirforum.com/user_avatar/forum.elixirforum.com/chrismccord/32/24233_2.png) [@chrismccord](https://forum.elixirforum.com/u/chrismccord)\
**Post date:** [March 18, 2022, 6:46pm UTC](https://forum.elixirforum.com/t/heex-syntax-reference-and-engine-extension-points/46677/2 "2022-03-18T18:46:35Z")

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1. The syntax reference and usage is well documented here [https://hexdocs.pm/phoenix\_live\_view/Phoenix.LiveView.Helpers.html#sigil\_H/2](https://hexdocs.pm/phoenix_live_view/Phoenix.LiveView.Helpers.html#sigil_H/2)

2. We don’t provide any extensions points at the moment, and it’s not likely something we’d be able to consider until after 1.0

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**Author:** ![arkadyan](https://forum.elixirforum.com/user_avatar/forum.elixirforum.com/arkadyan/32/10150_2.png) [@arkadyan](https://forum.elixirforum.com/u/arkadyan)\
**Post date:** [December 15, 2022, 8:43pm UTC](https://forum.elixirforum.com/t/heex-syntax-reference-and-engine-extension-points/46677/3 "2022-12-15T20:43:53Z")

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It looks like that documentation is now under [Phoenix.Component](https://hexdocs.pm/phoenix_live_view/Phoenix.Component.html#sigil_H/2).