Channels

Marketers often want to define their acquisition channels based on UTM and referrer data. Amplitude's channels let you create new properties retroactively, based on functions and operators you can apply across multiple existing properties. These don't affect your raw data and Amplitude computes them on the fly.

For example, you may want to understand the distribution of organic traffic to your site. Define a version of your channels that includes the known social and search domains at that time. When a new social or search channel becomes prevalent, you can update your organic search definition and your existing charts update retroactively to reflect the new definition.

Amplitude Default Channels

Every new Amplitude org and project gets a pre-built classifier called [Amplitude] Default Channels automatically. You don't need to configure anything to get started.

Amplitude creates it when you first open Data > Properties > Channels. It maps UTM parameters and referrer data into 29 GA4-aligned marketing channels, including:

Paid Search and Organic Search
Paid Social and Organic Social
Paid Video and Organic Video
Partner and External Referral
LLM Search and Paid LLM Search (AI-assisted referrals from tools like ChatGPT and Perplexity).
Email, Display, Affiliates, and Referral
Audio, SMS, and Mobile Push
Direct
Other (traffic that doesn't match any rule).

This gives Marketing Hub and the Global Agent useful channel breakdowns from day one, without requiring you to build a classifier from scratch.

The classifier is fully editable and deletable. You can rename it, modify rules, change conditions, or remove it entirely.

Best results with the browser SDK

The [Amplitude] Default Channels classifier works best with the Amplitude Browser SDK when you carefully manage set() and unset() calls on UTM properties. Inconsistent property handling can classify traffic as "Other" even when UTM values are present.

Upgrade to GA4-aligned defaults in an existing org

If your org was created before Amplitude introduced the GA4-aligned [Amplitude] Default Channels, you'll receive an upgrade prompt when you open Data > Properties > Channels. Click Build with the new logic to open the classifier builder pre-filled with the updated GA4-aligned rule set. Review the rules, rename the classifier if you like, and click Save to add it alongside your existing classifiers.

Amplitude never overwrites your existing classifiers. Your current channel definitions remain unchanged until you modify or delete them yourself.

You can also add the default classifier at any time without the upgrade prompt:

Navigate to Data > Properties > Channels.
Click + Add Channel Classifier.
The [Amplitude] Default Channels template opens automatically. Rename it if you like.
Customize the rules or click Save to add it as-is.

Amplitude adds the new classifier without changing any of your existing ones.

Create a channel

You must be an Admin or Manager to create a channel.

To create a channel, follow these steps:

Navigate to the Properties section of Amplitude Data and open the Channels tab.
Click + Add Channel Classifier. A pre-built, default channel definition screen opens. Optionally, click the default channel title (Channel) to edit the name. You can also add a description below it.
To begin creating the definition of the channel, start from the default template or click Clear Table to clear the table's contents. The default template uses the same GA4-aligned rule set as [Amplitude] Default Channels, covering 27 channels including LLM Search, Paid LLM Search, Audio, SMS, and Mobile Push.
You can add multiple properties to a row to create a more complex classifier.

Amplitude recommends using user properties rather than event properties for channels because Amplitude applies user properties to future events that a user triggers. For more information, go to About user properties and event properties.

Add one row for each channel you'd like to define. For example, you can add rows labeled Paid, Organic, Referral, and Direct to create a high-level channel definition.
Fill in the values for each row. Each cell must evaluate to True for an event to classify to that channel.
If you can define a channel as row A OR row B, add one row for A and one for B, then set the channel name to the same value for both rows.
Click Save. Amplitude labels channels in property dropdowns under the Channels category.

Channel classifier limits

Channel classifiers have two limits:

Maximum rows: 149 rows for each classifier.
Maximum cells: 1,000 total cells (rows × columns).

Amplitude restricts adding rows when either limit is reached. This means the effective maximum number of rows depends on the number of columns in your classifier. For example, with 10 columns, you can create approximately 100 rows before reaching the 1,000-cell limit.

Compare metrics between channels with Data Tables

Amplitude's Data Tables let you define metrics critical to your bottom line, such as CPA, AOV, and ROAS. Evaluate how these metrics perform between different channels by grouping by your channel on the left-hand column. Add other core dimensions like campaigns to break down these channels further.

Amplitude attributes metrics in different ways if a user has multiple touch points with different channels before converting. Amplitude has built attribution modeling into data tables to enable defining user attribution in your channels.

Applying a channel classifier before an attribution model can attribute values in potentially unexpected ways. For example, in a sequence consisting of:

CPC --> email --> website

Applying a channel classifier of CPC only filters out email and website. In this case, the attribution model attributes to CPC.

Use cases

Blended views: Create top-level blended views of all paid and all organic traffic to review how efficiency and performance have changed over time.
High-level channels: Break down your core metrics using the channel definitions you already use in Google Analytics and Adobe.
Channels with campaigns: Add a property denoting a campaign as a column in your channel definitions to break down metrics by campaign channel.
Attribution: Use channels with attribution models in data tables to evaluate the breakdown of a metric by first touch, last touch, or a custom attribution definition.

Special values

Amplitude evaluates these special values on events:

Value	Description
ANY	Captures explicitly set `none` values, or any other value that's set on the property.
(none)	Captures both explicitly and implicitly set `none` values.
blank	Captures both explicitly and implicitly set `none` values, or any other value that's set on the property.

Explicit and implicit none values

None values set both explicitly and implicitly appear as none in any Analytics chart.

Explicitly set none values appear when Amplitude receives the property with a value of null.

Implicitly set none values appear when Amplitude receives a property with no value.

Common questions

Amplitude's channel classifier offers the possibility to define acquisition channels that enables you to efficiently track your traffic sources. This article covers frequently asked questions about the channel classifier.

Who can create and modify channel definitions?

Channels classifier is currently only available to Growth and Enterprise users, and you must be an org admin or manager to create a channel and modify channel definitions.

Are users notified if channel classifiers change? Users and other admins aren't currently notified in this event. Any reports sourced from the channel classifier automatically updated to reference the most recent definition the next time someone loads or refreshes a report.

Where can users use these acquisition channels after they are defined?

Channels are stored as properties, which you can query through any analytics chart type (including Data Tables). Find your channels by navigating to Properties in Amplitude Data.

What kind of properties can be used in configuring a channel? Any (event, user, group) property can be used and mixed and matched in the definition. The channel classifier inherits the combination of the property types.

Are properties defined retroactively when a channel is created?

Yes. All existing charts update retroactively to reflect the new definition the next time someone refreshes the report.

How can I upload a channel definition?

It currently isn't possible to upload a channel classifier definition. If you'd like to create a channel classifier, you must manually create a column for every individual property you want to include in the definition.

Why can't I see my channels in a Data Table?

If you're using our pre-defined sample Channel Classifier, ensure that you are tracking the utm_medium and referring_domain properties in order for this to generate results in your Data Table. If you're not tracking these, either remove the column containing them from the Channel Classifier or instrument them as properties to start tracking them.

Is the referring domain captured by Amplitude, or do I have to pass this value?

You must send Referring Domain, as well as any other properties you track for attribution purposes (like UTM parameters, for example), to Amplitude.

Should I be setting channel classifiers to include initial_utm and utm_ properties so that initial and most recent campaign traffic gets bucketed correctly?

Unless you'd like to create a specific "Initial Channel", you shouldn't use or mix any of the initial_{} properties. It's best to focus on the standard/non-initial ones.

Can I input a regex formula when creating a channel classifier?

You can enter the regex as free-form text when creating a channel classifier.

Is the referring domain captured by Amplitude, or do I have to pass this value?

You must pass Referring Domain, as well as and any other properties you track for attribution purposes (like UTM parameters, for example), to Amplitude.

Why am I seeing '(none)' values when grouping by my channel in a Data Table?

You're seeing '(none)' values because you're querying on an event that occurred before that user property was ever sent. When using Amplitude, you're querying on the value of a user or event property at the time of the event. The '(none)' value showing for the property in the Data Table when grouping by your channel means that there's no value for that property.

Why can't I add more rows to my channel classifier?

Channel classifiers have two limits that restrict adding rows:

Maximum rows: 149 rows for each classifier.
Maximum cells: 1,000 total cells (rows × columns).

Amplitude restricts adding rows when either limit is reached. The UI tooltip shows the 149-row limit, but the 1,000-cell limit may prevent you from reaching that number. For example, with 10 columns, you can create approximately 100 rows before reaching the cell limit.

To add more rows, reduce the number of columns in your classifier, or simplify your channel definitions to use fewer cells.

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