Publish
iOS
Prepare design files
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Screenshots: @atik_gohel - Screenshots 
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App Icon: Expo - App Icon 
Create an app at App Store Connect
Fill the form
Upload build file with Transporter
Submit
After filling out the form and uploading the build file (.ipa), you can submit your app for review.
Fix and Submit
You’ll need to go through the review process, and often it takes several back-and-forth exchanges between you and Apple to get approved. Hang tight and keep your fingers crossed.
Done!
Android
Prepare design files
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Screenshots: @atik_gohel - Screenshots 
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App Icon: Expo - App Icon 
Create an app at Google Play Console
Fill the form
Upload build file (.aab)
Unlike Apple, you can upload the build file (.aab) directly to Google Play Console. Be careful about versioning since you won’t be able to upload the same version multiple times.
Submit
After uploading the build file (.aab), you can submit your app for review.
Fix and Submit
Just like with Apple, you also need to go through the review process for Android. It’s less strict than Apple though. Follow their requirements and wait for them to approve your app.