Packet Spy
Packet Spy lets players watch the network packets their Minecraft client sends and receives, with the contents shown live in a local web page opened from the game.
What it does
The mod shows incoming and outgoing packets as they happen. A local web interface, opened with the F12 key by default, lists each packet with its type, direction and category, and the fields of a selected packet are displayed as readable JSON that can be sorted and exported. Packet types that are not of interest can be muted so the traffic list stays readable, and related packets are grouped to show the flow of traffic over time. The interface comes in dark and light themes.
Packet Spy is a client-side mod for Fabric, released for 1.21 – 26.3 across 17 release versions, and it runs with Fabric API as its required dependency. The web interface runs on the local computer, and LAN access, which lets another device open the page, is disabled by default. Works in single-player and on multiplayer servers, where the server does not need the mod installed.
Key features
Live packet viewer
Incoming and outgoing packets appear in a list as the client handles them, with direction and type for each entry.
Search and filtering
Packets can be searched and filtered by type, direction or category to narrow down a large traffic log.
JSON packet contents
The fields of each packet are shown as readable JSON, sortable and exportable for the item being inspected.
Mute and group traffic
Unwanted packet types can be muted, and packets are grouped to visualize traffic flow.
Gallery
Compatibility
Latest build for each game version and loader.
26.x5 of 5 versions with builds
1.21.x12 of 12 versions with builds
Only full game releases are shown. This mod publishes no snapshot builds.
Requirements
Dependencies declared by the latest file for each loader.
Required 1
Use cases
Debugging a mod
A mod author can check which packets their code sends and receives while testing a feature.
Studying the protocol
Someone learning how the game communicates with a server can watch real packets and their fields.
Who it’s for: Mod developers and players who want to see the traffic their client exchanges with a server, in single-player or multiplayer.
How it compares
Where Is My Packet? is a client-side Fabric mod, open source under the MIT License, with files for 1.21.10 – 26.1.2. Packet Exception Logger is also open source under the MIT License and works for 1.21 – 26.2, but it can run on the client or the server, so either side is enough. PacketProfiler is client-side only, with a custom license that is not open source, and targets 26.2 – 26.3.
| Mod | Loaders | Game versions | Environment | Updated |
|---|---|---|---|---|
| Packet Spy | Fabric | 1.21 – 26.3 | Client-side only | 2026-10-02 |
| Where Is My Packet? | Fabric | 1.21.10 – 26.1.2 | Client-side only | 2026-04-20 |
| Packet Exception Logger | Fabric | 1.21 – 26.2 | Client or server, optional | 2024-11-22 |
| PacketProfiler | Fabric | 26.2 – 26.3 | Client-side only | 2026-09-21 |
Questions
Does Packet Spy require Fabric API?
Does the server need Packet Spy installed?
Can another device on the network open the web interface?
In the catalog
Packet Spy is one of 36,990 Utility mods on ModsFinder, and one of 25,772 Utility mods for Fabric. 8,071 mods support Minecraft 26.3.
Similar mods
What the author says
PacketSpy is a client-side Fabric mod for viewing the network packets your Minecraft client sends and receives in real time. Press F12 (can be rebound in settings) in-game to open the local web interface. From there you can search and filter packets, inspect their fields as JSON, sort packet traffic, mute noisy…
Official listing
- Modrinth page
- modrinth.com/mod/packet-spy
- Owner
- Ander507WasTaken
- Published
- 2026-01-01
- Updated on Modrinth
- 2026-10-02
- Facts verified
- 2026-10-15