{"id":"apps.what-does-files-that-differ-only-by-case-mean","url":"/faq/apps/what-does-files-that-differ-only-by-case-mean","category":{"id":"apps","title":"Apps"},"subcategory":{"id":"reliability","title":"Drive, safety and recovery"},"question":"Why does an app move fail with \"files that differ only by case\"?","alt_questions":["Case-sensitive drive app move error","Files would collide on the destination","Reformat drive as case-insensitive APFS","App won't move to case-sensitive drive"],"short_answer":"Your fast drive is case-sensitive and the app has files whose names differ only by capitals, so they'd clash. Nothing is changed; a standard (case-insensitive) APFS drive avoids it.","answer_markdown":"Your fast drive is formatted as **case-sensitive** while your Mac's built-in drive isn't, and this app contains files whose names differ only by capital letters. On the built-in drive they're treated one way, on the external drive another, so they would clash — and Storage Studio stops rather than risk a broken copy.\n\nNothing is changed. Most people never see this; if you do, the reliable fix is to use a drive formatted as standard (case-insensitive) APFS. See [external drives](/faq/external-drives/).","answer_html":"

Your fast drive is formatted as case-sensitive while your Mac's built-in drive isn't, and this app contains files whose names differ only by capital letters. On the built-in drive they're treated one way, on the external drive another, so they would clash — and Storage Studio stops rather than risk a broken copy.

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Nothing is changed. Most people never see this; if you do, the reliable fix is to use a drive formatted as standard (case-insensitive) APFS. See external drives.

","answer_text":"Your fast drive is formatted as case-sensitive while your Mac's built-in drive isn't, and this app contains files whose names differ only by capital letters. On the built-in drive they're treated one way, on the external drive another, so they would clash — and Storage Studio stops rather than risk a broken copy.\n\nNothing is changed. Most people never see this; if you do, the reliable fix is to use a drive formatted as standard (case-insensitive) APFS. See external drives.","tags":["error","drive format","case-sensitive"],"related":[{"id":"apps.why-did-an-app-move-fail","question":"Why did an app fail to move, and what should I do?","url":"/faq/apps/why-did-an-app-move-fail"}],"applies_to":"all","last_reviewed":"2026-10-01","title":"Why does an app move fail with \"files that differ only by case\"? — Storage Studio FAQ","description":"Your fast drive is case-sensitive and the app has files whose names differ only by capitals, so they'd clash. Nothing is changed; a standard (case-insensitive) APFS drive avoids it.","crumbs":[{"name":"Home","path":"/"},{"name":"FAQ","path":"/faq/"},{"name":"Apps","path":"/faq/apps/"},{"name":"Why does an app move fail with \"files that differ only by case\"?","path":"/faq/apps/what-does-files-that-differ-only-by-case-mean"}],"jsonld":{"@context":"https://schema.org","@type":"FAQPage","url":"https://storagestudio.us/faq/apps/what-does-files-that-differ-only-by-case-mean","inLanguage":"en","dateModified":"2026-10-01","mainEntity":[{"@type":"Question","name":"Why does an app move fail with \"files that differ only by case\"?","alternateName":["Case-sensitive drive app move error","Files would collide on the destination","Reformat drive as case-insensitive APFS","App won't move to case-sensitive drive"],"acceptedAnswer":{"@type":"Answer","text":"Your fast drive is formatted as case-sensitive while your Mac's built-in drive isn't, and this app contains files whose names differ only by capital letters. On the built-in drive they're treated one way, on the external drive another, so they would clash — and Storage Studio stops rather than risk a broken copy.\n\nNothing is changed. Most people never see this; if you do, the reliable fix is to use a drive formatted as standard (case-insensitive) APFS. See external drives.","url":"https://storagestudio.us/faq/apps/what-does-files-that-differ-only-by-case-mean"}}]},"fragment":"
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Apps · Drive, safety and recovery

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Why does an app move fail with "files that differ only by case"?

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Short answer: Your fast drive is case-sensitive and the app has files whose names differ only by capitals, so they'd clash. Nothing is changed; a standard (case-insensitive) APFS drive avoids it.

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Your fast drive is formatted as case-sensitive while your Mac's built-in drive isn't, and this app contains files whose names differ only by capital letters. On the built-in drive they're treated one way, on the external drive another, so they would clash — and Storage Studio stops rather than risk a broken copy.

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Nothing is changed. Most people never see this; if you do, the reliable fix is to use a drive formatted as standard (case-insensitive) APFS. See external drives.

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