> ## Documentation Index
> Fetch the complete documentation index at: https://help.airbridge.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Campaign Parameters

## What characters can be used for campaign parameters?

***

It is strongly recommended to use the following characters.

* Uppercase and lowercase letters
* Numbers
* `_`and `-`

For custom channels, it is strongly recommended to use the following characters.

* Lowercase letters
* Numbers
* `_`

## Are there length limitations for campaign parameters?

***

Yes, 256 characters per campaign parameter.

## The campaign parameter is different from what I created.

* Any `/`in channel names are replaced by`_`(e.g. `My/Channel`→ `My_Channel`)
* Any `#`in the campaign parameter values are replaced by `_`. (e.g. `ad_group=#MyGroup`→ `ad_group=_MyGroup`)

## Why do I see a `$$default$$` channel in my reports?

***

Airbridge tracking links follows a `https://abr.ge/@{app_name}/{channel}?{campaign_parameter}` format. If `channel` is empty when the tracking link is clicked, `$$default$$` is shown as its value.e.g. Campaign parameter data collected when clicking on `https://abr.ge/@airbridge_demo?campaign=abc`.

* channel: `$$default$$`
* campaign:`abc`

## Is it possible to not use a tracking link and use UTM paramters for attribution?

***

Yes, it is possible for both web and app events. Please see below for details.

| Event Source | UTM Attribution Setup                                                                                                                | UTM Attribution Example                                                                                                                                                       |
| ------------ | ------------------------------------------------------------------------------------------------------------------------------------ | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Web          | Turn on the [UTM parsing feature](/en/developers/web-sdk#utmparsing-automatic)                                                       | **URL** `https://example.com?utm_source=google&utm_campaign=my_campaign`<br />**Attribution**<br />Attributed Channel: `google`<br />Attributed Campaign: `my_campaign`       |
| App          | Contact your Airbridge CSM to turn on the UTM Attribution settings. (Will be provided through the Airbridge dashboard in the future) | **URL**<br />`example://detail/123?utm_source=google&utm_campaign=my_campaign`<br />**Attribution**<br />Attributed Channel: `google`<br />Attributed Campaign: `my_campaign` |

<link rel="alternate" hrefLang="en" href="https://help.airbridge.io/en/developers/campaign-parameters-faq" />

<link rel="alternate" hrefLang="ko" href="https://help.airbridge.io/ko/developers/campaign-parameters-faq" />