---
title: "ACME based Challenge Mode"
slug: "acme-based-challenge-mode"
updated: 2026-05-06T02:07:52Z
published: 2026-05-06T02:30:32Z
canonical: "help.12dsynergy.com/acme-based-challenge-mode"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://help.12dsynergy.com/llms.txt
> Use this file to discover all available pages before exploring further.

# ACME based Challenge Mode

ACME-based challenge mode is the most popular mechanism. It will renew your certificate and install it in the right place.

There are two types of certificates.

- [Fixed domain](/v1/docs/fixeddomain) (like synergy.myserver.com)
- [Wildcard](/v1/docs/wildcarddomain) (*.myserver.com).

Both of these require different steps, but **we recommend using a fixed domain for simplicity**.

Any ACME- compatible server can be used, but the 12d Synergy Certificate tool defaults to [**Lets****Encrypt**](https://letsencrypt.org).