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A channel group is one coherent inventory selection inside a campaign. It combines AdCP inventory dimensions without inventing new AdCP channel values. For example, mobile web display means:
It does not mean channel: "mobile_web". mobile_web is not an AdCP media channel.
Interchange uses the channel-group ID to split and label media buys, and a V3 request_proposals round uses the groups to choose which sellers to ask and which returned products to keep (see Proposal rounds follow your channel groups). It does not validate products you select against the group’s inventory definition, or translate that definition into package targeting. Murph and API clients must verify discovery evidence and seller product details before assigning channelGroupId.
Within one inventory dimension, values are alternatives (OR). Across populated dimensions, declared values combine (AND). A group with channels: ["ctv", "olv"] and deviceTypes: ["ctv", "mobile"] therefore allows either channel and either device, while still declaring both a listed channel and a listed device. If you need pairwise logic such as “CTV on CTV devices OR OLV on mobile devices”, make two channel groups.

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Why groups create media-buy boundaries

One downstream AdCP media buy cannot preserve arbitrary Boolean combinations across channel, property type, device type, and format. Interchange therefore uses this compilation rule:
If a campaign contains mobile-web-display and ctv, products assigned to those groups become separate media buys even when they use the same seller and currency. They remain part of one campaign.

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Save pre-built groups

Pass channelGroups to save_campaign on /mcp/v3. A preset is authoring shorthand. Interchange expands and saves the full definition with the preset version, so later preset changes do not silently change an existing campaign.
The available presets expand as follows: The simple channel presets deliberately make no property, device, or format assumption. For example, ctv means the AdCP CTV channel; it does not silently mean only a physical television device or only a CTV app.

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Define your own group

You can provide the same AdCP-aligned dimensions directly:
Use separate groups when combinations must not collapse into a cross-product. Do not put an alias such as mobile_web into channels; aliases belong in the group name or preset ID, while the saved inventory definition stays aligned to AdCP.

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Proposal rounds follow your channel groups

When a campaign has channel groups, a V3 request_proposals round uses them in three ways:
  1. Which sellers are asked. A seller is contacted only when at least one of the channels it declares can match a channel in one of your groups. Channel aliases match their AdCP value: a seller listed as audio matches streaming_audio. For an official platform integration, such as Spotify or Amazon, the platform’s own channel coverage is used. A seller that declares no channels is still asked, because nothing shows it cannot match.
  2. What each seller is told. Every contacted seller receives the union of your groups’ channels as the AdCP channels filter on its request. If a group names no channel, no channel filter is sent, because that group accepts every channel.
  3. Which products come back. A returned product whose channels, or whose creative format kinds, fit none of your groups is dropped, together with any proposal that allocates budget to it. The seller’s outcome reports the number dropped as channelExcludedProductCount. A product that does not declare a channel or format is kept.
The response lists the eligible sellers that were not contacted in skippedSellers: each entry names the seller, the channels it declares, and the reason channel_mismatch. At most 25 sellers are listed; total counts them all. If no eligible seller can match any group, the round ends failed with cohortError.code NO_ELIGIBLE_SELLERS and the same skippedSellers list. To include more sellers, add a group for their channel and start a new round with the new campaign revision. Seller narrowing needs every group to name at least one channel. If one group bounds only property type, device type, or format, that group admits sellers of any channel, so the round asks every eligible seller and sends no channel filter. Product filtering still applies the channel and format bounds of the groups that have them. A group that bounds only property type or device type turns filtering off, because neither sellers nor returned products declare those dimensions reliably. A round whose one seller is fixed by the buyer’s account, such as a sponsored buyer or an own-supply sandbox campaign, never lists that seller in skippedSellers. The seller still receives the channels filter, and its returned products are still filtered.

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Assign products when creating a media buy

Discover products, verify that the seller evidence matches one group, then pass that group’s ID when creating the draft. With save_media_buy, channelGroupId applies to all products in that creation call:
When using the batch create_media_buys operation directly, put channelGroupId on each product or proposal selection. Every selection needs a group ID when its campaign defines channel groups. A media buy records the group ID and name that created it. Define groups before the campaign creates its first ungrouped media buy. Once a saved selection or media buy references a group, keep it immutable; add a new group instead of removing or redefining it. The batch operation also accepts fully expanded channelGroups in campaign.create. Preset shorthand is available through V3 save_campaign; REST clients either send the canonical saved shape inline or create the campaign first and pass its campaignId. REST does not accept preset shorthand. Send name, source, and the expanded inventory snapshot:
Always pass product and proposal IDs exactly as discovery returned them. The qualified sf1: value in the example is illustrative; do not construct or decode it in a client.

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Report by the same group

Use the V3 get_delivery tool with the campaign_delivery report and the channel_group dimension:
To read one group only, add filters.channelGroupId. Ungrouped legacy media buys roll up under a null channel group rather than being guessed from their names, products, or delivery. Channel groups answer “which coherent inventory selection did the buyer ask for?” Campaign targeting answers “who, where, or when should it reach?” Keep those concepts separate even when both mention a dimension such as device.