Instagram says upload the highest resolution possible: what's the max?

Instagram's Creators help page says "Upload the highest resolution possible" and that "Video quality matters. People tend to engage more with high visual quality content." It gives no pixel number. The highest resolution a Sume Timeline render can produce for a vertical video is bounded by the schema: output.width and output.height are even integers from 256 to 2160, so the tallest 9:16 shape is about 1214x2160. The default, 1080x1920, is the safe choice.

That ceiling is only a ceiling for the container. The picture cannot hold more detail than the source clips have, and an upscale adds pixels without adding detail. So "highest possible" is limited by what you started with.

What Instagram's pages do and don't say

The Creators page gives the quality advice and the 3-minute recommendation for unconnected audiences, but no resolution or aspect ratio. The Reels feature page covers length: clips that add up to 20 minutes. Neither page states a pixel size for Reels, which is why this post does not give you one.

Compare YouTube, which does state a cap: its Shorts page says you can upload Shorts with a maximum resolution of 1080p. Instagram's wording is open-ended; YouTube's is a number.

The arithmetic for a 9:16 ceiling

At the 2160 limit on the tall edge, 9:16 width is 2160 x 9 / 16 = 1215. That is odd, and Timeline needs even values, so you choose 1214 or 1216. 1214x2160 is a hair narrower than 9:16 (0.5620 against 0.5625) and fits inside it; 1216x2160 is slightly wider. For a clean 9:16 the practical sizes are 1080x1920 and 720x1280.

If the source clips are 1080x1920, rendering 1214x2160 only scales them up by 12.5%. That is not what "highest resolution possible" means to a viewer. The advice pays off when your clips are higher than 1080p to begin with.

Rendering and checking

Set output explicitly and then confirm what you got. The sample renders a 1214x2160 file. Afterwards, extract a frame at the source size with video frames: omit max_edge and the frame keeps the clip's size, which lets you read the actual width and height of the result.

Video frames bills by its own Modal compute and always returns 202, so you poll the GET route. A render of 30 seconds bills one Timeline minute, $0.10.

curl -X POST https://api.sume.com/v1/timeline-1.0/render \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: reel-2160-001" \
  -d '{
    "audio": {
      "url": "https://media.sume.com/artifacts/artf_demo/voice.wav",
      "duration_seconds": 30
    },
    "video": [
      {
        "source_url": "https://media.sume.com/artifacts/artf_demo/hero.mp4",
        "start": 0,
        "duration": 30
      }
    ],
    "output": { "width": 1214, "height": 2160 }
  }'

A practical rule

Match the output to the best source you have. If the clips are 1080x1920, deliver 1080x1920. If they are higher, render at the higher size up to the 2160 edge, and let the app do its own compression. If you also publish to YouTube Shorts, remember that its page caps Shorts at 1080p, so a 2160-edge master is only useful on one of the two.

If you only have 1080p sources

Most generated clips are not 2160 pixels tall, so a 1214x2160 render is an upscale. Upscaling makes the file larger without adding detail, which is why this post recommends matching the output to the best source instead of the biggest legal number. A larger file also takes longer to upload from your phone or desktop, and Instagram will compress it again.

The Instagram creators page says people engage more with high visual quality content; it does not say that a larger frame size alone produces it. Quality also depends on lighting, motion, compression and how much text you burn in. Spend effort on the source clip first, then on the export.

What to do in practice

Leave output.width and output.height unset when a 1080x1920 file is enough, since that is the default. Raise them only when your source clips carry more detail than 1080 pixels across, because a larger frame cannot add detail the sources lack.

After the render finishes, read the delivered size with video inspect probe and keep a note of it beside the file, so you know what you uploaded.