SD cards are usually trouble-free storage. When they're full you can delete some files and carry on. 

Sometimes things go awry and the best option is to format the card - erasing all its data - and starting again. In theory that's simple as Windows can format any drive natively. But on occasion even Windows fails to help and is unable to format your card. Here's what to do when that happens.

(If your card has broken completely, check out our recommendations of the best microSD cards.)

What software should I use to format an SD card?

The SD Association - the consortium which sets out the standards for SD cards - has its own formatting utility which is free. You can download SD Formatter 4 from the SD association's website. It's 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.

How to format an SD card

The utility won't let you select any internal hard disks, 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 the 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.

What other options are there for formatting an SD card?

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.

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 camera's format option.

How to format an SD card