Output build files (image files)

The building process produces each time an image file.

The image file can refer to an executable, a program, or an ELF file. As one of the last build steps, the linker processes all object files by locating code, data, and symbols in sections in the final ELF file. The linker replaces all symbol references to code and data with addresses. A symbol table that maps addresses to symbol names is created. This table is used by debuggers. When an ELF file is converted to another format, such as HEX or binary, the symbol table is lost.

Depending on the application and the SoC, you can use one or several images.

The nRF Connect SDK build system places output images in the <build folder> folder when using sysbuild.

Note

Pass the optional parameter -vvv to west build to enable a more detailed Verbose Builds log, which includes the full commands used by the build system to generate the output build files.

Common output build files

The following table lists build files that can be generated as output when building firmware for supported board targets. The table includes files for single-core and multi-core programming scenarios for both Visual Studio Code and command-line building methods. Which files you are going to use depends on the application configuration and not directly on the type of SoC you are using.

File	Description	Programming scenario
zephyr.hex	Default full image. In a project with multiple images, several zephyr.hex files are generated, one for each image. zephyr is the value of CONFIG_KERNEL_BIN_NAME. The file is located in the build/<your_application_name>/zephyr directory.	Programming board targets with NSPE or single-image. Testing DFU procedure with nrfjprog (programming directly to device).
merged.hex	The result of merging all HEX files for all images for a specific core In multi-core builds, several merged_<core>.hex fields are generated, where <core> indicates the CPU core.	Programming multi-core application. Testing DFU procedure with nrfjprog (programming directly to device).
tfm_s.hex	Secure firmware image created by the TF-M build system in the background of the Zephyr build. It is used together with the zephyr.hex file, which is intended for the Non-Secure Processing Environment (NSPE). Located in build/tfm/bin.	Programming SPE-only and multi-core board targets.
zephyr.signed.bin	Image update file used to create dfu_application.zip for multi-core DFU. Can also be used standalone for a single-image DFU. Contains the signed version of the application. This file is transferred in the real-life update procedure, as opposed to HEX files that are transferred with nrfjprog when emulating an update procedure. Compatible with MCUboot. zephyr is the value of CONFIG_KERNEL_BIN_NAME. The file is located in the build/<your_application_name>/zephyr directory.	DFU process for single or multi-core board targets
zephyr.signed.hex	HEX file variant of the <file_name>.signed.bin file. Can also be used standalone for a single-image DFU. Contains the signed version of the application. Compatible with MCUboot. zephyr is the value of CONFIG_KERNEL_BIN_NAME. The file is located in the build/<your_application_name>/zephyr directory.	Programming single or multi-core board targets
zephyr.signed.encrypted.bin	Image update file used to create dfu_application.zip for encrypted multi-core DFU updates. Can also be used standalone for a single-image DFU. Contains the signed and encrypted version of the application. This file is transferred in the real-life update procedure, as opposed to HEX files that are transferred with nrfjprog when emulating an update procedure. Compatible with MCUboot. zephyr is the value of CONFIG_KERNEL_BIN_NAME. The file is located in the build/<your_application_name>/zephyr directory.	DFU process for single or multi-core board targets
zephyr.signed.encrypted.hex	HEX file variant of the <file_name>.signed.encrypted.bin file. Can also be used standalone for a single-image DFU. Contains the signed and encrypted version of the application. Compatible with MCUboot. zephyr is the value of CONFIG_KERNEL_BIN_NAME. The file is located in the build/<your_application_name>/zephyr directory.	Programming single or multi-core board targets
zephyr.signed.bin in mcuboot_secondary_app folder	Secondary slot variant of the zephyr.signed.bin file. Compatible with MCUboot in the direct-xip mode. zephyr is the value of CONFIG_KERNEL_BIN_NAME.	DFU process for single-core board targets.
zephyr.signed.hex in mcuboot_secondary_app folder	Secondary slot variant of the zephyr.signed.hex file. Compatible with MCUboot in the direct-xip mode. zephyr is the value of CONFIG_KERNEL_BIN_NAME.	Programming single-core board targets.
dfu_application.zip	Zip file containing both the MCUboot-compatible update images for one or more cores and a manifest describing its contents.	DFU process for both single-core and multi-core applications.
matter.ota	Matter-specific OTA image that contains a Matter-compliant header and a DFU multi-image package that bundles user-selected firmware images. matter.ota is the value of SB_CONFIG_MATTER_OTA_IMAGE_FILE_NAME.	DFU over Matter for both single-core and multi-core applications.
<file_name>.zigbee	Zigbee-specific OTA image that contains the Zigbee application with the Zigbee OTA header used for providing information about the image to the OTA server. The <file_name> includes manufacturer’s code, image type, file version, and comment (customizable by user, sample name by default). For example: 127F-0141-01020003-light_switch.zigbee.	DFU over Zigbee for both single-core and multi-core applications in the nRF Connect SDK v2.0.0 and later.
<version_string>_<number>.bin in lwm2m_carrier_divided_dfu folder	Set of application update images specific for LwM2M carrier. It is required for the divided FOTA procedure in the SoftBank network. See CONFIG_LWM2M_CARRIER_SOFTBANK_DIVIDED_FOTA for more information. The <version_string> is the value of SB_CONFIG_LWM2M_CARRIER_DIVIDED_DFU_VERSION. The <number> is a zero-padded three digit number that corresponds to the number of the file in the update sequence. For example: versionA_001.bin.	Divided FOTA over LwM2M using the LwM2M carrier library for single-core applications certified in the SoftBank network.

MCUboot output build files

Note

MCUboot’s direct-xip mode and the related SB_CONFIG_MCUBOOT_MODE_DIRECT_XIP and SB_CONFIG_MCUBOOT_MODE_DIRECT_XIP_WITH_REVERT Kconfig options are currently supported only on the single-core devices such as the nRF52 Series. For more details, see the more information section of the Developing with nRF52 Series page.

File	Description
dfu_application.zip	Contains the following: The MCUboot-compatible update image for one or more cores when MCUboot is not in the direct-xip mode and a manifest describing its contents (all related *.bin files and a manifest.json file). The MCUboot-compatible update image for the primary and secondary slots when MCUboot is in the direct-xip mode and manifest describing its contents (all related *.bin files and a manifest.json file).
dfu_mcuboot.zip	Contains two versions of MCUboot linked against different address spaces corresponding to slot0 (s0) and slot1 (s1) and a manifest JSON file describing their MCUboot version number (SB_CONFG_SECURE_BOOT_MCUBOOT_VERSION), nRF Secure Immutable Bootloader (NSIB) version number (CONFIG_FW_INFO), board type. This file can be used by FOTA servers (for example, nRF Cloud) to serve both s0 and s1 to the device. The device can then select the firmware file for the slot that is currently not in use. Created when the options SB_CONFIG_SECURE_BOOT_APPCORE and SB_CONFIG_BOOTLOADER_MCUBOOT are set.
zephyr.signed.bin	Signed variant of the firmware in binary format (as opposed to HEX). It can be uploaded to a server as a FOTA image. zephyr is the value of CONFIG_KERNEL_BIN_NAME.
signed_by_mcuboot_and_b0_mcuboot.bin	MCUboot update image for s0 signed by both MCUboot and NSIB. The MCUboot signature is used by MCUboot to verify the integrity of the image before swapping and the NSIB signature is used by NSIB before booting the image.
signed_by_mcuboot_and_b0_s1_image.bin	MCUboot update image for s1 signed by both MCUboot and NSIB. The MCUboot signature is used by MCUboot to verify the integrity of the image before swapping and the NSIB signature is used by NSIB before booting the image.
zephyr.signed.hex	Signed variant of the firmware in the HEX format. This HEX file is linked to the same address as the application. Programming this file to the device will overwrite the existing application. It will not trigger a DFU procedure. zephyr is the value of CONFIG_KERNEL_BIN_NAME.
zephyr.signed.bin in mcuboot_secondary_app folder	Secondary slot variant of the app_update.bin file intended for use when MCUboot is in the direct-xip mode. Created when the CONFIG_BOOT_BUILD_DIRECT_XIP_VARIANT Kconfig option is enabled. zephyr is the value of CONFIG_KERNEL_BIN_NAME.
zephyr.signed.hex mcuboot_secondary_app folder	Secondary slot variant of the app_signed.hex file intended for use when MCUboot is in the direct-xip mode. Created when the CONFIG_BOOT_BUILD_DIRECT_XIP_VARIANT Kconfig option is enabled. zephyr is the value of CONFIG_KERNEL_BIN_NAME.

SUIT output build files

The following table lists secondary build files that can be generated when building firmware update packages using the Software Updates for Internet of Things (SUIT) DFU procedure.

File	Description
root_with_binary_nordic_top.yaml.jinja2 app_envelope.yaml.jinja2 rad_envelope.yaml.jinja2	SUIT Manifest templates automatically placed in the sample directory after the first build of the SUIT: Device firmware update on the nRF54H20 SoC sample. They serve as the basis for generating the specific SUIT envelopes tailored to the requirements of different domains within the device (root, application, and radio).
root.suit application.suit radio.suit	Binary SUIT envelopes that are generated from their respective YAML manifest templates during the build process of the SUIT: Device firmware update on the nRF54H20 SoC sample. The root.suit contains embedded application core manifest (application.suit) and radio core manifest (radio.suit). The radio.suit is not generated for the UART version of the SUIT: Device firmware update on the nRF54H20 SoC. These files can be found in the build/zephyr directory after building the sample.

Other output build files

The following table lists secondary build files that can be generated when building firmware, but are only used to create the final output build files listed in the table above.

File	Description
zephyr.elf	An ELF file for the image that is being built. Can be used for debugging purposes.
zephyr.meta	A file with the Zephyr and nRF Connect SDK git hashes for the commits used to build the application. If your working tree contains uncommitted changes, the build system adds the suffix -dirty to the relevant version field.
tfm_s.elf	An ELF file for the TF-M image that is being built. Can be used for debugging purposes.
manifest.json	Output artifact that uses information from the zephyr.meta output file.
dfu_multi_image.bin	Multi-image package that contains a CBOR manifest and a set of user-selected update images, such as firmware images for different cores. Used for DFU purposes by Matter and Zigbee protocols.
signed_by_b0_mcuboot.bin	Intermediate file only signed by NSIB.
signed_by_b0_s1_image.bin	Intermediate file only signed by NSIB.