Note: Custom Blocks is only available on the Enterprise package. Not every Knak account has this feature. If you do not see Custom Blocks in your account, your package may not include it.
If you are interested in adding Custom Blocks, contact your Knak Customer Success Manager (CSM). They can talk with you about next steps for your account.
What Are Custom Blocks?
Custom Blocks are reusable content sections for emails and landing pages. You define the layout once. You reuse it across assets.
Instead of editing HTML, you fill in fields like text, links, or drop-downs.
Key Benefits
Reuse consistent layouts across campaigns
Prevent HTML editing errors
Speed up content creation
Customize content using simple inputs
Demo Video
Create A Custom Block
Create a Custom Block for your marketing team to reuse.
Open Custom Blocks
Go to Admin.
Select Custom Blocks from the left navigation.
Click Create Custom Block.
Create the Default Version (Required)
The default version serves as the fallback version of the Custom Block. It is used whenever an integration-specific variant is not available.
Enter the following information:
Name
Description
Custom HTML
Click Add Variable.
Enter the following information:
Name
Label
Type
Text Input
Text Block
Dropdown
Default Value
Click Create to save the variable.
Repeat these steps for any additional variables.
Configure Integration-Specific Variants (Optional)
You can create integration-specific versions of a Custom Block when additional code or syntax is required for a specific marketing automation platform.
Open the integration-specific variant you want to configure.
Update the HTML for the selected integration.
Save your changes.
Integration-specific variants use the same variables as the default version.
Example Use Cases:
The default HTML might use standard inline styles
A Marketo variant might include Marketo-specific tokens or tracking scripts
A HubSpot variant might use HubSpot module syntax
Save the Custom Block
Click Create Custom Block.
The Custom Block is now available to use in emails, landing pages, modules, and themes.
Add A Custom Block To An Asset
Add a Custom Block directly from the builder.
Drag a Custom Block element into your email or landing page
View the selection modal
Search or browse available blocks
Select a custom block and click Select Block.
After selection, the block loads on the canvas with a preview.
Edit Custom Block Content In An Asset
You edit content in Custom Blocks by using fields. You do not edit HTML.
Open Block Settings
Click the Custom Block on the canvas
Open the right-side panel
Update Block Variables
Each field maps to a variable created by your admin.
Text input → Single-line text
Text Block → Multi-line text
Dropdown → Select from options
Preview Your Custom Block
Knak updates the Custom Block preview as you edit its fields.
Preview Behavior
Keep these differences in mind when reviewing your preview:
The preview uses the default HTML version.
Integration-specific versions do not appear in the preview.
The final output may differ after syncing to your integration.
Knak sanitizes the HTML used to generate the preview.
Because the preview and final output are processed differently, always test your final output before sending or publishing.
How Preview Sanitization Works
Knak uses HTMLPurifier to sanitize Custom Block HTML for the preview. This helps the preview render safely while preserving supported formatting.
This sanitization applies to the preview. It does not modify or sanitize the Custom Block HTML that you save or use in the final output.
Preview sanitization supports common attributes, including:
style,class,id,lang, anddirAlignment, size, title, and background attributes
Table and cell attributes
Image attributes, such as
srcandaltLink attributes, such as
hrefandtarget
Test Your Custom HTML
Knak does not validate, correct, or sanitize the Custom Block HTML that you save for final output.
Before You Send or Publish
Check your HTML for syntax errors.
Review your Custom Block in Knak.
Test your email or landing page in its final environment.
Test any integration-specific version you use.
Fix HTML issues before sending or publishing.
Note: If your HTML contains a syntax or code error, Knak keeps the code as entered. The preview may not show exactly how that code will behave in the final output.
Preview sanitization does not mean that Knak validates, corrects, or sanitizes the HTML used in your final output.
Your team is responsible for reviewing and testing the HTML used in your Custom Blocks.
How Content Is Stored
Your inputs are saved inside the asset. They are not stored separately.
What This Means
Values are stored as structured data
Data stays tied to the block in your email
Each block instance can have different values
FAQs
How do I make a default that doesn’t show anything?
Add one of these codes as the default. Use only the code, with nothing else in the field. <p></p> or <p>​</p>
The default will be invisible in your asset.
Why can’t I see Custom Blocks in my account?
Custom Blocks is part of the Enterprise package. If your account is on a different package, the feature will not appear. Contact your Knak Customer Success Manager (CSM) to ask about adding it.
Need more help? Contact support via live chat within Knak using the chat bubble in the bottom right corner or email support@knak.com.