Antminer Firmware Update Guide

Updating the firmware on a Bitmain Antminer is a routine maintenance task, but doing it in the wrong order can leave a miner stuck in a boot loop or running at reduced hashrate. This guide covers the general update process that applies to most Antminer models (S19, S19 XP, S21, S21 XP, L7, L9, T19, T21 and others), whether you are installing the stock Bitmain firmware or a custom overclocking firmware.

Before you start

  • Write down the current settings. Pool address, worker name and password, frequency/voltage profile if it was already tuned. A factory reset during the update will erase these.
  • Check the exact model and board revision. Firmware built for one hashboard revision will not run correctly on another, even within the same model name (for example S19 vs S19 Pro vs S19j Pro use different images).
  • Make sure the power supply is stable. A brownout during flashing is one of the few things that can actually damage a control board, not just corrupt the firmware.

Updating through the web interface

Most Antminer control boards run a small web server reachable at the miner's IP address (see our IP Reporter guide if you don't know it). Log in, go to the System > Upgrade (or Overview > Firmware) page, select the firmware file supplied for your exact model, and confirm. The miner will reboot automatically; do not power it off during this step.

Updating via SD card

Some models, and most recovery situations, use an SD-card based update instead. The image is written to the card with a tool such as Etcher or Rufus, the card is inserted into the control board's SD slot, and the board is powered on. See our dedicated SD card flashing guide for the exact steps and common pitfalls (wrong card size, wrong image format, card not seated fully).

After flashing

  • Reconnect to the web interface and re-enter the pool/worker settings you noted down.
  • Give the miner a few minutes to detect all hashboards before judging the hashrate - boards can appear one at a time while temperature sensors stabilize.
  • Monitor the hashrate and board temperatures for the first hour. A sudden temperature spike is more often a loose fan connector after reassembly than a firmware problem.

When a custom firmware makes sense

Stock firmware is tuned conservatively for warranty and cooling reasons across all climates. A custom build, matched to your specific unit and cooling setup, can recover some of that margin as extra hashrate or lower power draw per TH. If you are considering this route, see how our custom ASIC firmware service works before buying a generic third-party image, since a mismatched profile is the most common cause of an unstable overclock.

See also