Etcher is a free, open-source application for writing operating-system images to SD cards and USB drives on Windows, macOS and Linux. Also called balenaEtcher, it transfers an image onto removable media and checks the written data. Its graphical interface centers on choosing the image, selecting its destination and starting the flash.
Image writing
Etcher copies an image byte by byte, carrying its disk layout onto the destination rather than placing the downloaded file inside an existing folder. This suits bootable Linux images and operating-system images distributed for devices that use SD cards. The resulting drive contains the image’s contents and layout, replacing what was previously on it.
An image can come from a local file or a URL. Etcher also handles compressed images in ZIP, GZ, Bzip2 and XZ formats, alongside uncompressed images and DMG files. With a compressed source, the destination needs room for the expanded image; the smaller archive size does not describe the space that will be written.
Drive selection
The drive selector determines which connected device receives the image. Etcher hides system drives by default and provides warnings to reduce the chance of selecting a disk that contains the computer’s operating system. It also warns about unsuitable targets, such as a locked SD card or a drive that is too small for the image.
Flashing replaces the contents of the whole selected drive, so Etcher does not require the card or USB drive to be formatted beforehand.
Validation and boot support
Etcher’s validation phase checks that the image data was written correctly. This helps distinguish a completed write from one affected by a faulty card, drive or connection. Validation concerns the copied data; the image itself still determines what the destination can boot.
Because Etcher does not transform images to add missing boot support, Windows installation ISOs that require additional preparation do not become bootable through a raw flash alone. Etcher also does not create persistent storage for a Linux live USB, so it cannot add an area for retaining that live system’s changes between sessions.
