AuthBack
by litetex
AuthBack lets players keep playing on a Fabric server while Mojang's authentication services are unreachable, by falling back to locally cached responses.
What it does
When a server's authentication step fails because Mojang's web services are down, AuthBack substitutes answers it stored earlier. Those answers come from earlier successful requests and are kept on the local machine for a period of time. A player who has joined the server once within the past 36 days can therefore log in during an outage, and the mod also keeps profile content such as skins displayed where possible. The client generates and stores a keypair that acts as a backup for logging in when the official authentication servers cannot be reached.
Installation is needed on the server and on each client that connects to it, because a server that does not have the mod cannot verify these backup logins. Either side can run AuthBack alone, and neither needs it to play normally. The mod is published for Fabric only, across seven release versions 1.21.10 – 26.3, and it is open source under the GNU Affero General Public License v3.0 only. Fabric API is required, and Mod Menu is optional for opening the settings screen.
Key features
Cached authentication responses
Earlier replies from Mojang's web services are stored locally and reused when the services stop responding.
Offline-tolerant login window
A player who has joined the server within the past 36 days can still connect during an outage, as long as the cache covers that join.
Local fallback keypair
The client creates and keeps a keypair that is used to authenticate with servers when Mojang's servers are unavailable.
Configuration in the game options
Settings are changed from the Online options screen or from Mod Menu, and environment variables prefixed with AUTHBACK can override them for each side.
Compatibility
Latest build for each game version and loader.
Only full game releases are shown. This mod publishes no snapshot builds.
Requirements
Dependencies declared by the latest file for each loader.
Required 1
Optional 1
How it compares
AuthSecured is open source under the MIT License and runs on Fabric for 1.20 – 26.2, so its version range overlaps with AuthBack's only in part. InvalidPlayerBypassList is a server-side only Fabric mod, open source under the CC0 1.0 Universal license, for 1.21 – 26.1.2, and it does not cache authentication replies. EZLogin is a client-side only Fabric mod under a Creative Commons non-commercial license and is not open source; it is built for 26.2 alone.
| Mod | Loaders | Game versions | Environment | Updated |
|---|---|---|---|---|
| AuthBack | Fabric | 1.21.10 – 26.3 | Client or server, optional | 2026-09-17 |
| AuthSecured | Fabric | 1.20 – 26.2 | Not published | 2026-09-16 |
| InvalidPlayerBypassList | Fabric | 1.21 – 26.1.2 | Server-side only | 2026-05-17 |
| EZLogin | Fabric | 26.2 | Client-side only | 2026-07-21 |
Questions
Does AuthBack need Fabric API?
Does the server have to run AuthBack too?
Which game versions does AuthBack support?
In the catalog
AuthBack is one of 8,499 Technology mods on ModsFinder, and one of 4,201 Technology mods for Fabric. 8,071 mods support Minecraft 26.3.
More from litetex
Similar mods
What the author says
Allows you to play as normal even when Mojang's authentication servers are down. Additionally also improves the networking behavior. If an outage occurs the previously cached responses are used.
Official listing
- Modrinth page
- modrinth.com/mod/authback
- Owner
- litetex
- Published
- 2025-11-23
- Updated on Modrinth
- 2026-09-17
- Facts verified
- 2026-10-15