Formatting an SD card is not a difficult process. You probably already know that it's as simple as right-clicking on the drive as it appears in Windows' File Explorer and choosing Format... Then, in most cases using the Quick Format setting is all you need to do to erase the card's contents in a couple of seconds.
The files aren't actually erased, only the pointers to them, which is why a full format takes so much longer. But since you're reading this, you're probably having trouble using your usual method. But we're here to help, and we've got several options you can try out and hopefully get that SD card formatted.
First, check the little switch on the side of the card (if present) isn't set to LOCK. If it is, the card is read-only and cannot be formatted. Just slide it away from lock and try again.
If you haven't yet tried out the built-in format facility in Windows, ensure your SD card is inserted into your laptop or a USB card reader if your laptop or PC doesn't have the appropriate slot.
Open up Windows Explorer (Windows key +E is the shortcut) and click on This PC. Find your SD card in the list of drives, right click on it and choose Format...
In the window that opens, you shouldn't need to change any settings. Just make sure Quick Format is ticked and then click Start.
How to format an SD card when Windows refuses?
If for some reason the card fails to format, there are couple of alternatives to try.
Method 1. Use SD Formatter
The SD Association - the consortium which sets out the standards for SD cards - has its own formatting utility which. You can download SD Formatter 4 from the SD association's website. It's free and available for Windows and macOS.
It couldn't be simpler to use, offering two main options: Quick Format and Overwrite Format. Try the former as it's much faster, but if that doesn't work, try again but select the latter mode.
The utility won't let you select any internal hard disks, which is reassuring, but it will show any connected USB storage, so be careful to ensure you've chosen the right drive before formatting. Don't assume just because it tells you the type of SD card that you have actually selected one: we tried connecting a USB flash drive and the utility told us it was an SDHC card.
Before you do format your card, you may also want to try and recover any photos or other files from the card. This can work even if they're corrupted.
Method 2: use another device
Many dash cam manufacturers advise formatting your SD card once per month, and always provide this facility on the dash cam itself. You should find a 'Format' option in the settings menu. Alternatively, if the camera has no display, you should find the format option in the companion app.
Similarly, all digital cameras - including DSLRs - which take SD cards include a menu option to format it. If you're having problems formatting in Windows, try your dash cam, drone or camera's format option.
If none of these methods work, it's likely your SD card is boken and will need replacing. Check out our recommendations of the best microSD cards.