# Custom CSS for new Knowledge Base

**URL:** <https://community.hubspot.com/t/custom-css-for-new-knowledge-base/141616>\
**Category:** Knowledge Base Tool\
**Tags:** content\
**Created:** [October 26, 2025, 10:43pm UTC](https://community.hubspot.com/t/custom-css-for-new-knowledge-base/141616 "2025-10-26T22:43:24Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![WSawyer](https://avatars.discourse-cdn.com/v4/letter/w/73ab20/32.png) [@WSawyer](https://community.hubspot.com/u/WSawyer)\
**Post date:** [October 26, 2025, 10:43pm UTC](https://community.hubspot.com/t/custom-css-for-new-knowledge-base/141616/1 "2025-10-26T22:43:24Z")

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Finally migrated to the new Knowledge Base over the weekend.

What happened to the support for Custom CSS?

There’s one immediate major issue after the migration and that the default background colour of the active category in the left navigation, it’s using a couple of shades of blue for the background, but there isn’t a theme colour setting for that.

I’ve got the CSS required to reset it to just white background, but I can’t find how to use the CSS with the new knowledge base?

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**Author:** ![WSawyer](https://avatars.discourse-cdn.com/v4/letter/w/73ab20/32.png) [@WSawyer](https://community.hubspot.com/u/WSawyer)\
**Post date:** [October 26, 2025, 10:48pm UTC](https://community.hubspot.com/t/custom-css-for-new-knowledge-base/141616/2 "2025-10-26T22:48:25Z")

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Ah, found the Custom Header HTML settings in **Settings** \> **Content** \> **Knowledgebase** , had to first make sure the new (migrated) Knowledge Base was selected. Then added a \<style\> block to the Header HTML with my custom CSS. Seems to work.

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**Author:** ![Jaycee\_Lewis](https://d10pqhm3lwygmk.cloudfront.net/user_avatar/community.hubspot.com/jaycee_lewis/32/61352_2.png) [@Jaycee\_Lewis](https://community.hubspot.com/u/Jaycee_Lewis)\
**Post date:** [October 27, 2025, 3:46pm UTC](https://community.hubspot.com/t/custom-css-for-new-knowledge-base/141616/3 "2025-10-27T15:46:59Z")

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Hey @WSawyer 👋 Thanks for taking the time to come back and let us know what worked. — Jaycee