# Tools

[中文]

## `idf.py flash` default behavior (fast reflash)

The default behavior of `idf.py flash` has changed. When `*_flashed.bin` files exist in the build directory (e.g. from a previous successful flash), `idf.py flash` now performs fast reflashing: it only writes the flash regions that changed, which speeds up repeated flashing during development. After flashing, it verifies that the device flash content matches the expected binaries; if verification fails, a full flash is performed.

If you prefer the previous behavior where all binaries are always written in full (regardless of existing `*_flashed.bin` files), you can force a complete flash by using the full flash mode: run `idf.py flash -a` or `idf.py flash --all`. This ensures that every binary is re-written to the device, which is recommended when working with brand-new, empty, or erased chips, or whenever you want to disable fast reflash and incremental flashing.

For more details, see Flash the Project: flash in the IDF Python Tools guide.

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