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fullstack-build/tslog

Universal TypeScript and JavaScript logger with pretty terminal output, structured fields-first JSON, secret masking and zero runtime dependencies.

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What is it?

tslog is a logging library for TypeScript and JavaScript that runs on Node.js, browsers, Deno, Bun, workers and React Native with one API. By default it prints colorized, readable output in an interactive terminal and plain text when output is piped or run in CI, while a flat, fields-first JSON format can be enabled for production log pipelines.

The library covers common needs such as log levels with custom level support, child loggers that inherit settings and bound fields, and masking of keys, paths and regex matches so secrets do not reach log output. Errors and stack traces are formatted and serializable, and source maps map positions back to original TypeScript files on Node, Bun and Deno.

For output routing, tslog offers transports for files, HTTP endpoints, in-memory ring buffers and worker threads, plus presets that emit pino-compatible or OpenTelemetry OTLP/JSON output. Its core package has zero runtime dependencies, and a slim subpath is available for size-sensitive browser bundles.

Key features

  • 01Same API across Node.js, browsers, Deno, Bun, workers and React Native
  • 02Pretty output colored in terminals and plain when piped, with optional JSON
  • 03Secret masking by key name, JSON path, regex or hashed placeholder
  • 04Child loggers that inherit settings and bound fields
  • 05Pluggable transports for files, HTTP, ring buffers and worker threads
  • 06Zero runtime dependencies and TypeScript types

Use cases

  • Adding consistent logging to a Node.js service with JSON output in production
  • Logging from a shared module that runs in both browser and server code
  • Masking passwords and tokens before logs leave the process
  • Shipping logs to a file, HTTP collector or OpenTelemetry endpoint

Quick start

  1. 1

    Install tslog from npm

    npm install tslog
  2. 2

    Import Logger and log a message

Things to know

  • Requires Node.js 22 or newer and is ESM-only, with no CommonJS require() support.
  • Version 5 is a breaking redesign, so upgrading from v4 needs code changes.

Topics

#logging#typescript#javascript#logger#structured-logging#json#observability#error-handling#exceptions#json-api

FAQ

What is tslog?
Universal TypeScript and JavaScript logger with pretty terminal output, structured fields-first JSON, secret masking and zero runtime dependencies. tslog is a logging library for TypeScript and JavaScript that runs on Node.js, browsers, Deno, Bun, workers and React Native with one API. By default it prints colorized, readable output in an interactive terminal and plain text when output is piped or run in CI, while a flat, fields-first JSON format can be enabled for production log pipelines.
Is tslog free to use? What license does it have?
tslog is open source under the MIT license. Check the license terms before using it in commercial products.
Is tslog still maintained?
Actively maintained. The last commit to tslog was on Oct 20, 2026.
What can I use tslog for?
Adding consistent logging to a Node.js service with JSON output in production Logging from a shared module that runs in both browser and server code Masking passwords and tokens before logs leave the process Shipping logs to a file, HTTP collector or OpenTelemetry endpoint
How do I install tslog?
Install tslog from npm: npm install tslog Import Logger and log a message
Where can I get tslog?
The source code and installation instructions are on GitHub: https://github.com/fullstack-build/tslog

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