The following ad group level target overrides are available in the Google Ads API.

## Override bidding strategies

A bid strategy can only be set at the campaign level. For example, if a
campaign has already been assigned a `TARGET_ROAS`
[strategy](https://developers.google.com/google-ads/api/reference/rpc/v26/Campaign#bidding_strategy_type), setting `TARGET_CPA`
fields in one of its ad groups will have no effect.

Similarly, setting bids manually will have no effect if you are using a
campaign-level bid strategy that doesn't support them. For example, if your
campaign uses `TARGET_ROAS` as a standard bidding strategy, and you set max CPC
values for individual keywords in that campaign, the keyword-level bids will be
ignored without errors. If you were to switch to manual bidding, the
keyword-level bids would then take effect. Read more in the
[Help Center](https://support.google.com/google-ads/answer/2732132).

## Override Target ROAS at the ad group level

The [`target_roas`](https://developers.google.com/google-ads/api/reference/rpc/v26/TargetRoas#target_roas) field of a
[`TargetRoas`](https://developers.google.com/google-ads/api/reference/rpc/v26/TargetRoas) bidding scheme, or a
[`MaximizeConversionValue`](https://developers.google.com/google-ads/api/reference/rpc/v26/MaximizeConversionValue) scheme with
its [`target_roas`](https://developers.google.com/google-ads/api/reference/rpc/v26/MaximizeConversionValue#target_roas) field
set, can be overridden at the ad group level by setting the ad group's
[`target_roas`](https://developers.google.com/google-ads/api/reference/rpc/v26/AdGroup#target_roas) field. The other fields of
the bidding scheme cannot be overridden.

To remove an override, unset [`target_roas`](https://developers.google.com/google-ads/api/reference/rpc/v26/AdGroup#target_roas)
of the ad group by sending a mutate request with an empty field value while
still supplying the path in the update field mask. Note that `target_roas` on an
ad group is only supported for standard campaign-level strategies and Search
portfolio strategies; attempting to override `target_roas` for other portfolio
strategies will result in an error.

You can retrieve the effective `target_roas` value of an ad group with the
[`effective_target_roas`](https://developers.google.com/google-ads/api/reference/rpc/v26/AdGroup#effective_target_roas) field and
its source with the
[`effective_target_roas_source`](https://developers.google.com/google-ads/api/reference/rpc/v26/AdGroup#effective_target_roas_source) field.

## Override Target CPA at the ad group level

The [`target_cpa_micros`](https://developers.google.com/google-ads/api/reference/rpc/v26/TargetCpa#target_cpa_micros) field of a
[`TargetCpa`](https://developers.google.com/google-ads/api/reference/rpc/v26/TargetCpa) bidding scheme (including both standard
campaign-level and portfolio `TargetCpa` strategies), or a
[`MaximizeConversions`](https://developers.google.com/google-ads/api/reference/rpc/v26/MaximizeConversions) scheme with its
[`target_cpa_micros`](https://developers.google.com/google-ads/api/reference/rpc/v26/MaximizeConversions#target_cpa_micros) field
set, can be overridden at the ad group level by setting the ad group's
[`target_cpa_micros`](https://developers.google.com/google-ads/api/reference/rpc/v26/AdGroup#target_cpa_micros) field. The other
fields of the bidding scheme cannot be overridden.

To remove an override, unset
[`target_cpa_micros`](https://developers.google.com/google-ads/api/reference/rpc/v26/AdGroup#target_cpa_micros) of the ad group
by sending a mutate request with an empty field value while still supplying the
path in the update field mask.

You can retrieve the effective value of `target_cpa_micros` for an ad group from
the [`effective_target_cpa_micros`](https://developers.google.com/google-ads/api/reference/rpc/v26/AdGroup#effective_target_cpa_micros) field and its source
from the [`effective_target_cpa_source`](https://developers.google.com/google-ads/api/reference/rpc/v26/AdGroup#effective_target_cpa_source) field.

## Override Target CPC at the ad group level

For Demand Gen campaigns using the [`TargetCpc`](https://developers.google.com/google-ads/api/reference/rpc/v26/TargetCpc)
bidding scheme (`Campaign.target_cpc`), the
campaign-level [`target_cpc_micros`](https://developers.google.com/google-ads/api/reference/rpc/v26/TargetCpc#target_cpc_micros)
can be overridden at the ad group level by setting the ad group's
[`target_cpc_micros`](https://developers.google.com/google-ads/api/reference/rpc/v26/AdGroup#target_cpc_micros) field. To remove
an override so the campaign-level `target_cpc_micros` takes effect again, unset
[`target_cpc_micros`](https://developers.google.com/google-ads/api/reference/rpc/v26/AdGroup#target_cpc_micros) on the ad group
by sending a mutate request with an empty field value while still supplying the
path in the update field mask.

You can retrieve the effective target CPC (returned as an `int64` value in
micros of the account currency, even though the field name omits `_micros`) and
its source from the read-only [`effective_target_cpc`](https://developers.google.com/google-ads/api/reference/rpc/v26/AdGroup#effective_target_cpc) and
[`effective_target_cpc_source`](https://developers.google.com/google-ads/api/reference/rpc/v26/AdGroup#effective_target_cpc_source) fields on `AdGroup`. By
contrast, [`TargetCpv`](https://developers.google.com/google-ads/api/reference/rpc/v26/TargetCpv) (`message TargetCpv {}`) is an
empty message at the campaign level, so for Video campaigns using `TargetCpv`,
[`target_cpv_micros`](https://developers.google.com/google-ads/api/reference/rpc/v26/AdGroup#target_cpv_micros) sets the CPV bid
directly at the ad group level rather than overriding a campaign-level target.