Image sizes

A Creative Session makes each image at one size. When the draft names no size, that size is 1024×1024. Many destinations need something else: Meta’s feed image must be at least 1080 pixels wide, so a 1024×1024 image does not fit Meta. This page lists the sizes a session can make, shows how to see which ones your destination accepts, and explains how to choose one.

The sizes

Size	Aspect ratio	Gemini tier
1024×1024	1:1 (the default)	1K
1080×1080	1:1	2K
1910×1000	1.91:1	2K
1080×1620	2:3	2K
1620×1080	3:2	2K
1080×1440	3:4	2K
1440×1080	4:3	2K
1080×1350	4:5	2K
1350×1080	5:4	2K
1080×1920	9:16	2K
1920×1080	16:9	2K

Every image comes out at exactly the size you ask for, whichever engine makes it: when an engine works at a nearby ratio, Apostra crops the result to your size, keeping the part most likely to hold the subject. A Meta image post picks its own size when the draft names none: 1080×1350 (4:5), or another of Meta’s feed ratios when the campaign’s placement calls for it.

What a size costs

The size does not change what Apostra charges. Images made with the Scope3-funded engine carry no retail IU charge at any size (see Creative generation). The Gemini tier is Gemini’s own billing tier: Gemini bills an image up to 1024 pixels on its longer side at its 1K tier, and a larger one at its 2K tier. It affects your own bill only when your image engine is a Gemini connection that uses your own key. On any other engine the tier does not apply, and the read below shows null for it. The default is 1024×1024 because every engine makes that size directly and Gemini makes it at its lower tier.

See which sizes fit your destination

Read an image Creative Session with get:

{ "kind": "creative_session", "id": "cs_123", "sourceId": "campaign_456" }

The session object carries imageSizes. save_creative_session returns the same field whenever it returns the session, including when you save a draft.

"imageSizes": {
  "current": { "width": 1024, "height": 1024 },
  "options": [
    { "id": "1024x1024", "aspectRatio": "1:1", "params": { "width": 1024, "height": 1024 }, "providerTier": "1K", "default": true },
    { "id": "1080x1080", "aspectRatio": "1:1", "params": { "width": 1080, "height": 1080 }, "providerTier": "2K" },
    { "id": "1910x1000", "aspectRatio": "1.91:1", "params": { "width": 1910, "height": 1000 }, "providerTier": "2K" }
  ],
  "destinations": [
    {
      "label": "Meta Feed Image Ad",
      "sellerName": "Meta",
      "formatOptionRef": { "scope": "publisher", "publisher_domain": "facebook.com", "format_option_id": "meta_image_feed" },
      "fits": ["1080x1080", "1910x1000", "1080x1350"]
    }
  ]
}

The example shows three of the eleven options.

Field	What it says
`current`	The size the draft generates at, as `width` and `height`. A draft that names no size holds the default, so this always has a value.
`options[].id`	The size, written `<width>x<height>`.
`options[].aspectRatio`	The aspect ratio, in AdCP’s `aspect_ratio` format.
`options[].params`	The size as AdCP canonical image parameters. Send it unchanged to choose this size.
`options[].providerTier`	Gemini’s billing tier for this size when the session’s engine is Gemini, otherwise `null`.
`options[].default`	`true` on the size an image draft gets when it names none.
`destinations[].label`	The destination format’s name.
`destinations[].sellerName`	The seller or platform, when known.
`destinations[].formatOptionRef`	The format option, as AdCP’s `format_option_ref`.
`destinations[].fits`	The ids of the sizes this format accepts.
`destinationsTruncated`	`true` when Apostra found more destination formats than the list shows. The list is then partial, so a size that fits every listed format may not fit one left out. Absent otherwise.

Apostra decides which sizes fit from the format’s own declaration: its accepted sizes, minimum and maximum width and height, and accepted aspect ratios. The destinations are:

the format the draft names, such as the Meta image post; or
for a campaign session that names none, the image formats of the products the campaign’s media buys use, up to 20, always listed in the same order.

When neither applies, or the formats cannot be read, destinations is null. That means Apostra does not know, not that no size fits. The text the tool returns says the same in one line, for example: “Image sizes: 1080×1080 (1:1), 1910×1000 (1.91:1), 1080×1350 (4:5) fit the destination format; the current 1024×1024 does not.”

Choose a size

Send an option’s params as the draft’s request.params when you save the draft:

{
  "campaignId": "campaign_456",
  "idempotencyKey": "garden-launch-1080",
  "draft": {
    "request": {
      "format_kind": "image",
      "params": { "width": 1080, "height": 1080 },
      "creative_brief": { "prompt": "A garden product photograph." }
    }
  }
}

You can send an aspect ratio instead, as "aspect_ratio": "1:1" in the request, and Apostra uses that ratio’s size from the table. A saved draft keeps its size: to make the image at another size, save a new draft.

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The sizes

What a size costs

See which sizes fit your destination

Choose a size

​The sizes

​What a size costs

​See which sizes fit your destination

​Choose a size

The sizes

What a size costs

See which sizes fit your destination

Choose a size