# micronucleus/micronucleus

ATTiny usb bootloader with a strong emphasis on bootloader compactness.

Repository: https://github.com/micronucleus/micronucleus
Canonical: https://ross.abutalabs.com/products/micronucleus
Language: C
License: NOASSERTION
License Family: other
Topics: avr, micronucleus, bootloader, v-usb, usb
Last push: 2026-02-06T23:31:23+00:00

## Health v2 (maintenance only)
Score: 52/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 66, release rhythm 8, longevity 100
- inputs: {"age_days": 5092, "days_push": 208, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: no_license
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1759, forks 381 (observed 2026-08-28T04:05:32.538843+00:00)

## What it is
Micronucleus is a compact USB bootloader for AVR ATtiny microcontrollers, built on V-USB with all configurations under 2KB. It includes a cross-platform libusb-based command-line upload tool for flashing firmware over USB.

## Use cases
- upload firmware to attiny over usb
- bootloader for attiny85 digispark
- smallest usb bootloader for avr attiny
- flash arduino-compatible attiny firmware via usb
- program attiny without external programmer
- update firmware on usb attiny device

## When to choose
- you need a tiny (<2KB) USB bootloader for ATtiny microcontrollers
- you want to flash firmware over USB without a dedicated programmer
- you work with Digispark-style ATtiny85 boards

## When to avoid
- you use ATmega or ARM microcontrollers instead of classic ATtiny
- you need a protected bootloader section or advanced USB features
- you need high-throughput firmware uploads

## Facets
- artifact type: cli-tool
- maturity: active
- function: embedded, developer-tools, cli
- domain: embedded-systems, hardware, developer-tools
- platform: windows, cross-platform, cli, embedded
- tags: avr, attiny, bootloader, v-usb, firmware-upload, libusb, microcontroller, linux, macos

## Member repositories
- micronucleus/micronucleus (main) score 52

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:05:32.538843+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T03:27:17.764577+00:00, confidence not recorded.
  - readme: https://github.com/micronucleus/micronucleus (fetched 2026-08-28T04:05:32.538843+00:00, sha 20c7ce232c08)
- Data as of 2026-08-30T08:39:29.467469+00:00.