# Use dynamic content
> Show different HTML blocks to different subscribers in one campaign, based on their data or past activity.
Source: https://www.kualo.com/knowledgebase/mailmachine-campaigns/use-dynamic-content
Updated: 2026-06-10
---
:::info
Dynamic content is an advanced, HTML-based feature. You'll work in the HTML editor's source-code mode and write a little markup. If you're not comfortable with HTML, **[display conditions](/knowledgebase/mailmachine-campaigns/show-content-with-display-conditions)** offer a simpler, visual alternative.
:::
Dynamic content shows different blocks to different people inside a single campaign - product recommendations, location-based offers, behavioural triggers - without building separate emails. You define conditional blocks that change based on subscriber data or past campaign activity.
## How it's written
All dynamic-content instructions go inside square brackets; anything outside them is sent as-is. A basic conditional looks like this:
```
[IF variable operator constant]
[ELSEIF variable operator constant]
[ELSE]
[ENDIF]
```
## Variables, operators and constants
**Variables** are what you test - list fields (wrapped in backticks) or previous campaign activity. Supported data types are boolean, integer (-8,388,608 to 8,388,608), string (up to 255 characters) and date (in `YYYY-MM-DD HH:MM:SS`, 24-hour clock).
**Campaign activity** lets you react to what a subscriber did: `MAILING(id)` refers to a campaign and `LINK(id)` to a link, with statuses `OPENED` and `CLICKED`. You'll find a campaign's ID at the end of its stats URL, and a link's ID after `link=` in the click-report URL.
**Operators:**
- Text: `LIKE`, `NOT LIKE`
- Numbers and dates: `=`, `!=`, `<`, `<=`, `>`, `>=`
- Activity: `IS`, `IS NOT`
- Combining: `AND`, `OR`
**Constants** go in double quotes for text, date or integer values, like `"NY"`, `"2010-08-02 10:00:00"` or `"5"`.
## Example expressions
```
`email` LIKE "%hotmail%" -> address contains "hotmail"
`id` > "1000" -> list ID over 1000
MAILING(34342) IS OPENED -> opened campaign 34342
(`email` LIKE "%hotmail%") AND (MAILING(34342) IS OPENED)
```
The variable and constant must be the same data type, and you can group expressions with parentheses.
## Functions
`MOD(N,M)` returns the remainder of N divided by M - handy for picking a fraction of your list:
```
[IF MOD(`id`,10) = 5]
You are a winner!
[ELSE]
Sorry! Try again!
[ENDIF]
```
## Troubleshooting
**It shows as plain code** - make sure everything is inside brackets, you're in HTML/source mode, and every `[IF]` has a matching `[ENDIF]`.
**Conditions don't evaluate** - variable names must match field names exactly (case-sensitive) and be wrapped in backticks, and data types must match (don't compare text to numbers).
**ELSEIF/ELSE don't work** - keep the order IF, ELSEIF, ELSE, ENDIF, and check each block is valid HTML.
**Complex expressions fail** - build up gradually, use parentheses to group, and check spacing around operators.
If dynamic content won't behave, [open a support ticket](/knowledgebase/getting-started/how-to-create-a-support-ticket-in-mykualo).
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_Source: Kualo Knowledgebase — https://www.kualo.com/knowledgebase/mailmachine-campaigns/use-dynamic-content · © Kualo Ltd._