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User123455 For optimal quality, especially for desktop users, Instagram allows higher resolution uploads. For mobile users, it's recommended to post with exact resolutions such as 1080 X 1080 (1), 1080 X 1350 (4), 1620 X 1080 (3), or 1920 X 1080 (16) to avoid compression.
If you want to ensure your account is private, you can make your account private so that only approved followers can see your posts. This can be done through the settings menu in the Instagram app.
For more information on controlling your visibility and privacy settings, you can refer to the Instagram Help Center.