Knak’s mission is to empower our customers to build their assets in a no code environment, as such we removed the custom html block. If you’re struggling to build something please reach out to your CSM or our support team and we can advise you on the best path forward and/or help reenable this feature
Why Use Custom HTML?
Knak’s flexible Email Builder supports most layouts without custom code. However, there may be rare cases where custom HTML is useful:
Adding HTML5 video or anchor links
Using advanced CSS effects (e.g., animations)
Embedding live content from external providers (e.g., product recommendations, maps, countdowns)
⚠️ Use custom HTML cautiously. Errors can impact the entire email layout. Always test thoroughly.
We recommend building layouts with structure blocks where possible.
How to Add Custom HTML in the Builder
Drag the HTML content block into your email or landing page.
Click the block.
Use the code editor in the right-hand panel to paste your HTML.
HTML tags allowed in the Builder
The HTML content will automatically correct some issues like HTML tags that are left open, and strip out code that cannot be used, such as script tags or iframe tags (these code tags are not allowed by the major part of email clients, can cause deliverability problems or security risks for the editor an the applications that runs it).
Allowed Tags List:
'img', 'style', 'meta', 'center', 'del', 'html', 'head', 'comment', 'title', 'link', 'body', 'font', 'iframe', 'nobr', 'video', 'source', 'noscript', 'first', 'map', 'area', 'head', 'button', 'color', 'input', 'span', 'details', 'summary', 'wc-mega-menu', 'wc-mega-footer'
Expand to view the Allowed Attributes per Element
Expand to view the Allowed Attributes per Element
video: src, width, height, style, id, class, data-*, title
iframe: src, width, height, style, id, class, data-*, title
meta: name, content, http-equiv, itemprop, style, id, class, data-*, title
time: itemprop, datetime, style, id, class, data-*, title
body: style, width, height, id, class, data-*, title
style: type, style, id, class, data-*, title
link: href, rel, type, style, id, class, data-*, title
table: align, border, cellpadding, cellspacing, width, valign, style, bgcolor, table, id, class, data-*, title
tr: align, style, valign, width, bgcolor, class, id, data-*, title
td: align, style, valign, width, bgcolor, class, id, data-*, title, colspan, rowspan
th: align, style, valign, width, bgcolor, class, id, data-, title, scope, colspan, rowspan
div: style, width, bgcolor, class, id, itemscope, itemtype, itemprop, mktoname, data-w-id, data-layout, data-url, data-*, title
span: class, itemscope, itemtype, itemprop, id, style, data-*, title
p: style, width, bgcolor, class, id, data-*, title
a: align, style, width, bgcolor, name, target, href, class, id, data-*, title
img: align, style, width, height, border, src, class, id, data-*, alt, title
button: align, style, width, bgcolor, name, target, href, class, id, data-*, title
Adding CSS in Custom HTML
Gmail removes CSS that isn’t placed in the <head> section. Any CSS written inside an HTML block may not render correctly.
✅ Add custom styles to the Custom Head HTML section in the advanced settings tab under the asset "Info" section.
Embedding and Adjusting iframes
You can embed external content like videos or maps using iframes in HTML blocks.
Step-by-Step:
Use this format:
<iframe src="[URL]" width="100%" height="800px"></iframe>
Replace
[URL]with your content source.Adjust
widthandheightas needed.Use Preview Mode to view the iframe correctly.Embedding and Adjusting iframes in Knak's Custom HTML Blocks
Important Guidelines for Scripts
Scripts are not allowed in the body of your landing page.
Add scripts to the Custom Head HTML section only.
Scripts are not allowed in the body of the landing page due to security reasons. We recommend adding the script section of the custom HTML under the Custom Head HTML in the advanced settings tab located in the asset "Info" section.
Do not place
<div>or other structural elements in the Custom Head HTML sectionThis will break the parser since this is considered invalid HTML.
The
<head>should only contain metadata like<meta>,<style>,<script>,<title>, and<link>tags. Move structural elements into the body using a custom HTML block.
Video Walkthrough of adding HTML
Need more help? Contact support via live chat within Knak using the chat bubble in the bottom right corner or email support@knak.com