threads.media.image_size_max - letmepost.dev

What it checks

byteLength <= 8_000_000 per image.

Why

Meta’s Threads API documents an 8 MB per-image cap on the create-container endpoint. Larger images are rejected upstream with code 100, error subcode 2207003 or similar.

Failure response

{
  "error": {
    "code": "preflight_failed",
    "rule": "threads.media.image_size_max",
    "platform": "threads",
    "message": "Image is 9500000 bytes; Threads allows at most 8000000.",
    "remediation": "Re-encode the image under 8000000 bytes (Threads's per-image limit is 8 MB)."
  }
}

Remediation

Re-encode at lower quality or smaller dimensions. JPEG q=85 + max 2048 px is a sensible default:

magick input.jpg -quality 85 -resize 2048x2048\> output.jpg