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I've come across several USB drives that don't work in Mac computers at all (I've tested on 3 Mac computers, so it's not a problem with the USB ports in a particular Mac machine). No drive appears in the desktop, and I can't find it mounted in /media/, nothing! A similar thing happens in a Linux machine (Raspberry Pi OS).

One of the drives is a no-name drive, but the other one is Philips. And they're NOT using the NTFS filesystem (even then, it should appear as a read-only filesystem in a Mac anyway).

So, why do they only work in Windows? Is there anything in their firmware that might make them work only with Windows machines?

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Pendrive can have MBR or not. File system (exFAT, FATs) can be created at the beginning of the drive, where should be MBR. The difference can make drive not visible in some operating systems.

Check both ways: with MBR at the first sector and partition beginning at 2048 sector (you can do that in fdisk, Disks or GParted), and other way: without MBR but having file system from sector 0 (created on whole drive, /dev/sdb, with mkfs.exfat/mkfs.fat).

If the drive will work - that means you have found the solution.

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Put them into Linux machine (Raspberry Pi is enough) and run dmesg and lsusb to make sure it sees them at all and what it thinks about them.

Then, if you find out they aren't recognized as mass storage devices, you've found the issue: those are non-standard devices and use a special driver in Windows. Never buy such crap stuff again.

Every "standard usb pen drive" should report itself as a mass storage, which is seen as a block device in Linux. We use fdisk -l /dev/sdX, lsblk and blkid to see the block devices structure. (Some hints will already be seen from dmesg run: if there is a recognizable partition table, it'll be printed.) In particular, blkid will detect if there's a supported file system, and which one.

The typical structure is as such: the drive has a partition table, likely MBR (some systems have difficulties with having GPT on removable devices). That partition table has a single partition of type, I think, 0x7 or 0xc. This will be recognized correctly by any system you'll encounter. If you see something different, that might be the cause. In such case, feel free to create structure that you'll like.

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