What is one-line-logger?

fastify/one-line-logger — explained in plain English

Analysis updated 2026-07-15 · repo last pushed 2026-07-01

★ 47JavaScriptAudience · developerComplexity · 2/5ActiveSetup · easy

Mindmap

mindmap
  root((repo))
    What it does
      Reformats JSON logs
      Single-line output
      Adds color by default
    Tech stack
      JavaScript
      Node.js
      Fastify plugin
    Use cases
      Debugging routes
      Scanning terminal logs
      Monitoring requests
    Customization
      Custom log levels
      Timestamp patterns
      Toggle colors

mindmap root((repo)) What it does Reformats JSON logs Single-line output Adds color by default Tech stack JavaScript Node.js Fastify plugin Use cases Debugging routes Scanning terminal logs Monitoring requests Customization Custom log levels Timestamp patterns Toggle colors

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What do people build with it?

USE CASE 1

Make Fastify server logs readable as single-line text instead of dense JSON.

USE CASE 2

Add color to terminal logs to quickly spot errors and incoming requests.

USE CASE 3

Customize log timestamps and create custom log levels with unique colors.

What is it built with?

JavaScriptNode.jsFastify

How does it compare?

	fastify/one-line-logger	netflix/ember-batch-request	eugeny/instacode
Stars	47	48	45
Language	JavaScript	JavaScript	JavaScript
Last pushed	2026-07-01	2023-03-24	2023-05-23
Maintenance	Active	Dormant	Dormant
Setup difficulty	easy	moderate	easy
Complexity	2/5	3/5	1/5
Audience	developer	developer	developer

Figures from each repo's GitHub metadata at analysis time.

How do you get it running?

Difficulty · easy Time to first run · 5min

Requires an existing Fastify application to register the plugin.

So what is it?

one-line-logger is a plugin for Fastify, a popular web framework for Node.js. It takes the raw, hard-to-read JSON that Fastify normally spits out when logging requests and reformats it into a clean, single-line message that's easy to scan at a glance. When you build an app with Fastify, it automatically logs details about incoming requests as JSON. That format is great for computers, but tough for humans to parse quickly. This tool transforms that messy block of data into a simple, readable format like: "2022-08-11 01:08:02 - info - GET / - incoming request." You just plug it into your existing Fastify setup, and it handles the formatting automatically. This is built for developers who run Fastify apps and prefer reading their server logs in plain text. If you're staring at a terminal trying to debug why a specific route is failing, scrolling through walls of JSON can be frustrating. With this, you get a clean, chronological list of what hit your server and when, making it much easier to spot problems. The tool includes a few practical options to customize the output. It adds color to your logs by default to help different parts of the message stand out, which is useful when you're scanning a long file. You can also turn the colors off, display only the time instead of the full date, or provide a custom pattern for how the timestamp should look. Beyond the standard log levels like "info" and "error," you can set up your own custom levels with their own colors. For example, if you wanted a specific log type called "foo" highlighted in yellow, the setup makes that straightforward. These options let you tweak the output to fit exactly what you need to see when monitoring your application.

Copy-paste prompts

Prompt 1

Add one-line-logger to my Fastify app so server logs print as readable single-line messages instead of JSON.

Prompt 2

Configure one-line-logger to disable colors and show only the time instead of the full date in my Fastify logs.

Prompt 3

Set up a custom log level called 'warn' in one-line-logger that prints in yellow for my Fastify application.

Frequently asked questions