axt

Turn structured logs to something readable on your local dev machine.

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Structured logs are great. But ugh, what a mess:

{"time":"2025-08-24T21:51:45.549605+02:00","level":"INFO","msg":"API request completed","status_code":200,"response_time_ms":127,"response_size_kb":24.7}
{"time":"2025-08-24T21:51:45.549671+02:00","level":"INFO","msg":"feature-flag:set","dark_mode":true,"beta_features":false,"thingy":null}

Your server app shouldn't concern itself with making logs useable on dev machines. But you really want something like this:

Hide timestamps with `--hide time`

Use emojis for log levels with `--emoji`

And you want to highlight if someone leaves in a nasty unstructured log:

🪵  something without proper JSON

Well, you gotta use axt (it's German for axe, btw. ...and a cool way to spell axed)

How to use

Start your application and pipe its output through axt. E.g.:

./my-application | axt

Your logging lib might use a variety of property names for the three important parts of a log (as far as axt is concerned)

The defaults (as specified by go's slog lib) are:

• level
• msg
• time

But you can change them with these run-time flags.

  -l, --level string       define name of the level property (default "level")
  -m, --message string     define name of the message property (default "msg")
  -t, --time string        define name of the time property (default "time")

Additionally, you can configure your output with these options:

  --time-in string     given time format used by time property. Uses go's time convention; or use 'Unix' | 'UnixMilli' | 'UnixMicro' for Unix epoch timestamps.(default "RFC3339")
  --time-out string    print time in this format. Uses go's time convention (default "15:04:05.000")
  --emoji              display levels as emoji instead of text
  --linebreak string   "always" | only after "json" | "never" (default: always)
  --hide string        hide a property. Use the flag multiple times to hide more than one.

For defining your own time input and output format refer to the go documentation of the time format module

Examples:

• Using Open Telemetry: ./otel-app | axt -m EventName -t Timestamp -l SeverityText

• Elastic Common Schema: ./spring-app | axt -t @timestamp -l log.level

• Only hours, minutes and micro seconds air | axt -time-out 04:05:000

• Hide time timeless-app | axt --hide time

Protips:

• Alias axt with your runtime flags to a command that makes it shorter to use

  "alias and-my-axt=axt -m EventName -t Timestamp -l SeverityText --time-in Unix --time-out 15:04:05.000000 --emoji --linebreak never"

• Add the pipe through axt in a Makefile of your project for the benefit of your colleagues

Install

Brew

Install with

brew tap ctholho/ctholho
brew install axt

See below, in Verify Provenance how to verify your build with SLSA Level 3 compliance guarantees.

Go install

go install github.com/ctholho/axt@latest

If GOPATH is not part of your PATH, add axt globally for users of zsh:

echo "alias axt=$(go env GOPATH)/bin/axt" >> ~/.zshrc

Verify Provenance

Builds in the "Releases" section of this repository are built with the SLSA Level 3 Compliant Go builder, which comes with strong guarantees that nobody tampered with this build, if you verify the build.

[ For up to date information head over to SLSA verifier ]

To verify builds follow these steps:

First, download the matching intoto.jsonl file for your downloaded binary.

Next, install the slsa-verifier:

$ go install github.com/slsa-framework/slsa-verifier/v2/cli/[email protected]

Finally, use slsa-verifier for axt like this:

slsa-verifier verify-artifact <PATH TO BINARY> \
  --provenance-path <PATH TO INTOTO.JSONL> \
  --source-uri github.com/ctholho/axt \
  --source-tag <VERSION NUMBER WITH LEADING v>

# For example:
slsa-verifier verify-artifact /opt/homebrew/bin/axt \
  --provenance-path ~/Downloads/axt-darwin-arm64.intoto.jsonl \
  --source-uri github.com/ctholho/axt \
  --source-tag v0.7.0

Development

As a handy helper during development use debug/debug.go to simulate a server.

1. Build the axt binary with go build -o axt
2. Use the binary on the debug file: `go run debug/debug.go | ./axt

Roadmap

• Color theming
• Property highlighting