Publish to the stores with fastlane.

In the studio, pick the fastlane export and select every store size you target. Render. Download the ZIP.

fastlane/
├── screenshots/
│   ├── en-US/iPhone69/    01.png  02.png  …
│   ├── en-US/iPhone67/    …
│   └── en-US/iPhone65/    …
├── metadata/
│   └── android/en-US/images/phoneScreenshots/  01.png  02.png  …
├── README.txt
└── appscreen-manifest.json

Unzip into the root of your iOS / Android project. The folder tree merges with anything fastlane already uses there.

One-time setup of an App Store Connect API key (recommended over login + 2FA prompts):

1. App Store Connect → Users and Access → Integrations → App Store Connect API → Generate API Key. Role: Marketing (sufficient for screenshots; least privilege).
2. Download the .p8 private key. Note the Key ID and Issuer ID shown in the table.
3. Place the key somewhere fastlane can read it (~/.appstoreconnect/private_keys/AuthKey_KEYID.p8 is the convention).

Append to your fastlane/Fastfile:

lane :screenshots do
  app_store_connect_api_key(
    key_id: ENV["ASC_KEY_ID"],
    issuer_id: ENV["ASC_ISSUER_ID"],
    key_filepath: ENV["ASC_KEY_PATH"],
    in_house: false
  )

  deliver(
    skip_metadata: true,
    skip_binary_upload: true,
    skip_screenshots: false,
    overwrite_screenshots: true,
    force: true   # skip the manual confirm step
  )
end

Then run:

fastlane screenshots

All locales × every iPhone size in the bundle land in App Store Connect as a draft. You review and submit.

One-time service account setup:

1. Google Cloud Console → create a service account in the project linked to your Play account. Grant role Service Account User.
2. Generate a JSON key for that service account. Save as play-credentials.json (gitignore it).
3. Play Console → Users and permissions → invite the service account email. Grant Manage store presence (covers screenshots and store-listing text). Apply to the apps you publish.

Append to your Fastfile:

lane :play_screenshots do
  supply(
    package_name: "com.example.app",
    json_key: "play-credentials.json",
    skip_upload_apk: true,
    skip_upload_aab: true,
    skip_upload_metadata: true,
    skip_upload_changelogs: true,
    skip_upload_images: true,
    skip_upload_screenshots: false,
    track: "production"
  )
end

fastlane play_screenshots

Lands as a pending draft in Play Console. Review and roll out yourself.

The bundle is just files; any CI flow that already runs fastlane can pull it during a release build. Two common patterns:

1. Manual checkout: download the ZIP from AppScreen, commit the fastlane/screenshots and fastlane/metadata folders, run fastlane in CI on tag push.
2. Stored in CI artifact: upload the ZIP to the same CI artifact store you use for builds; expand into fastlane/ before the lane runs. Useful if you don't want generated PNGs in version control.

Example GitHub Actions step:

- name: Unzip AppScreen bundle
  run: |
    unzip -q appscreen-bundle.zip -d .
- name: Publish screenshots
  env:
    ASC_KEY_ID: ${{ secrets.ASC_KEY_ID }}
    ASC_ISSUER_ID: ${{ secrets.ASC_ISSUER_ID }}
    ASC_KEY_PATH: ${{ secrets.ASC_KEY_PATH }}
  run: bundle exec fastlane screenshots

Render every language you support inside one bundle (each maps to the correct en-US, es-ES, de-DE folder). Fastlane pushes them all in one run.

1. Asset failed validation on iOS: typically a non-RGB / alpha-channel PNG. AppScreen's fastlane export already alpha-flattens for iOS, so this only happens if you swapped a manual file in. Re-render the bundle.
2. 401 INVALID_PROVIDER from supply: service account isn't invited in Play Console yet, or the role is too narrow. Add Manage store presence.
3. Wrong device folder: deliver expects iPhone69 / iPhone67 / iPhone65. The export uses these exact names already.