These docs are for v5.1. Click to read the latest docs for v2024.1.

Using GELF

GELF ("Graylog Extended Log Format") is a structured log event format that's implemented for logging libraries in many programming languages. Seq can receive GELF events via UDP, and supports common features such as compression and chunking.

GELF is not enabled out-of-the-box, and must be enabled one of two ways:

  • On Windows, the Seq.Input.Gelf app must be installed and configured
  • On Docker, the datalust/sqelf container must be deployed alongside Seq

Enabling GELF on Windows

On Windows, the GELF input is installed into Seq as a Seq App.


1. Install the app package

In Settings > Apps, choose Install from NuGet. The app package id is Seq.Input.Gelf.

2. Start an instance of the app

From the apps screen, choose Add Instance and give the new GELF input a name.

The default settings will cause the GELF input to listen on localhost port 12201. Choose a different port if required.

Select Save Changes to start the input.

3. Configure Windows Firewall

Ensure UDP port 12201 (or the selected port, if you specified a different one), is allowed through Windows Firewall.

4. Log some events!

That's all there is to it. Events ingested through the input will appear in the Events stream. If the input doesn't work, check for diagnostic events raised by the input app (there is some status information shown under the app instance name).

Events ingested by the input will be associated with the default None API key, which can be used to attach properties, apply filters, or set a minimum level for the ingested events.

Enabling GELF in Docker

For Docker, the app is deployed as a Docker container that is expected to run alongside the Seq container. The datalust/sqelf image accepts UDP GELF payloads on port 12201, and forwards them over HTTP to the Seq ingestion endpoint specified in the SEQ_ADDRESS environment variable.

To run the container:

$ docker run \
    --rm \
    -it \
    -p 12201:12201/udp \
    -e SEQ_ADDRESS= \

Container configuration

A sqelf container can be configured using the following environment variables:

SEQ_ADDRESSThe address of the Seq server to forward events tohttp://localhost:5341
SEQ_API_KEYThe API key to use-
GELF_ADDRESSThe address to bind the UDP GELF server to0.0.0.0:12201
GELF_ENABLE_DIAGNOSTICSWhether to enable diagnostic logs and metrics (accepts True or False)False

Quick local setup with docker-compose

The following is an example docker-compose file that can be used to manage a local Seq container alongside sqelf in your development environment to collect log events from other containers:

version: '3'
    image: datalust/sqelf:latest
      - seq
      - "12201:12201/udp"
      SEQ_ADDRESS: "http://seq:5341"
    restart: unless-stopped
    image: datalust/seq:latest
      - "5341:80"
    restart: unless-stopped
      - ./seq-data:/data

The service can be started using docker-compose up:

$ docker-compose -p seq up -d

To collect logs from Docker's logging infrastructure, see Collecting Docker container logs.