asc-screenshot-resize

asc screenshot resize

Use this skill to resize screenshots to the exact pixel dimensions required by App Store Connect and validate they pass upload requirements. Uses the built-in macOS sips tool — no third-party dependencies needed.

Required Dimensions

iPhone

Display Size	Accepted Dimensions (portrait × landscape)
6.9"	1260 × 2736, 2736 × 1260, 1320 × 2868, 2868 × 1320, 1290 × 2796, 2796 × 1290
6.5"	1242 × 2688, 2688 × 1242, 1284 × 2778, 2778 × 1284
6.3"	1206 × 2622, 2622 × 1206, 1179 × 2556, 2556 × 1179
6.1"	1125 × 2436, 2436 × 1125, 1080 × 2340, 2340 × 1080, 1170 × 2532, 2532 × 1170
5.5"	1242 × 2208, 2208 × 1242
4.7"	750 × 1334, 1334 × 750
4"	640 × 1096, 640 × 1136, 1136 × 600, 1136 × 640
3.5"	640 × 920, 640 × 960, 960 × 600, 960 × 640

Note: 6.9" accepts screenshots from 6.5", 6.7", and 6.9" devices. 6.3" accepts from 6.1" and 6.3". 6.1" accepts from 5.4", 5.8", and 6.1".

iPad

Display Size	Accepted Dimensions
13"	2064 × 2752, 2752 × 2064, 2048 × 2732, 2732 × 2048
11"	1668 × 2420, 2420 × 1668, 1668 × 2388, 2388 × 1668, 1640 × 2360, 2360 × 1640, 1488 × 2266, 2266 × 1488
iPad Pro 2nd gen 12.9"	2048 × 2732, 2732 × 2048
10.5"	1668 × 2224, 2224 × 1668
9.7"	1536 × 2008, 1536 × 2048, 2048 × 1496, 2048 × 1536, 768 × 1004, 768 × 1024, 1024 × 748, 1024 × 768

Apple Watch

Device	Dimensions
Ultra 3 (49mm)	422 × 514, 410 × 502
Series 11 (46mm)	416 × 496
Series 9 (45mm)	396 × 484
Series 6 (44mm)	368 × 448
Series 3 (42mm)	312 × 390

Mac

Dimensions
1280 × 800
1440 × 900
2560 × 1600
2880 × 1800

Apple TV

Dimensions
1920 × 1080
3840 × 2160

Workflow

1. Fix Unicode filenames

macOS screenshots often contain hidden Unicode characters (e.g., U+202F narrow no-break space) that cause sips and other tools to fail with "not a valid file". Always sanitize first:

python3 -c "
import os
for f in os.listdir('.'):
    clean = f.replace('\u202f', ' ')
    if f != clean:
        os.rename(f, clean)
        print(f'Renamed: {clean}')
"

2. Check current dimensions

sips -g pixelWidth -g pixelHeight screenshot.png

3. Validate App Store readiness

Check for alpha channel and color space issues before uploading:

sips -g hasAlpha -g space screenshot.png

App Store Connect rejects screenshots with alpha transparency. Remove it by round-tripping through JPEG:

sips -s format jpeg input.png --out /tmp/temp.jpg
sips -s format png /tmp/temp.jpg --out output.png
rm /tmp/temp.jpg

Batch-strip alpha from all PNGs in a directory:

for f in *.png; do
  if sips -g hasAlpha "$f" | grep -q "yes"; then
    sips -s format jpeg "$f" --out /tmp/temp.jpg
    sips -s format png /tmp/temp.jpg --out "$f"
    rm /tmp/temp.jpg
    echo "Stripped alpha: $f"
  fi
done

4. Resize a single screenshot

# Portrait iPhone 6.5" (1284 × 2778)
sips -z 2778 1284 input.png --out output.png

Note: sips -z takes height first, then width: sips -z <height> <width>.

5. Batch resize all screenshots in a directory

mkdir -p resized
for f in *.png; do
  sips -z 2778 1284 "$f" --out "resized/$f"
done

6. Generate multiple device sizes from one source

mkdir -p appstore-screenshots
# iPhone
sips -z 2868 1320 input.png --out appstore-screenshots/iphone-6.9.png
sips -z 2778 1284 input.png --out appstore-screenshots/iphone-6.5.png
sips -z 2622 1206 input.png --out appstore-screenshots/iphone-6.3.png
sips -z 2532 1170 input.png --out appstore-screenshots/iphone-6.1.png
sips -z 2208 1242 input.png --out appstore-screenshots/iphone-5.5.png

7. Verify output

sips -g pixelWidth -g pixelHeight -g hasAlpha resized/*.png

Confirm all files show the target dimensions and hasAlpha: no.

Guardrails

• sips stretches images to fit exact dimensions. For best results, use source screenshots captured at or near the target aspect ratio.
• Always output to a separate file or directory (--out) to preserve originals.
• App Store Connect requires PNG or JPEG format. sips preserves the input format by default.
• Screenshots must not include alpha transparency. Always validate with sips -g hasAlpha before upload.
• Color space must be sRGB. If screenshots use Display P3, convert with: sips -m "/System/Library/ColorSync/Profiles/sRGB IEC61966-2.1.icc" input.png --out output.png.