SweetLemon Lab

Free developer, AI, and productivity tools that run entirely in your browser. No signup, no tracking, no nonsense.

Utility

Unit Converter

Convert between units of length, weight, area, volume, temperature, and speed — instant, offline, no signup.

Utility

Time

Convert timestamps, durations, timezones, date diffs, and calendars — all in one place.

Utility

Markdown Editor

Write and preview Markdown with a live three-pane editor — no signup, no server, runs entirely in the browser.

Utility

QR Code Generator

Generate QR codes for URLs, text, and contact info instantly.

coming soon
Utility

UUID / Hash / Base64

Generate UUIDs, compute hashes, and encode or decode Base64 strings.

coming soon
Developer

JSON Formatter

Format, validate, and minify JSON with syntax highlighting.

coming soon
Developer

JWT Decoder

Decode and inspect JSON Web Tokens without sending them to a server.

coming soon
Developer

Regex Tester

Test regular expressions against sample text with live match highlighting.

coming soon
Developer

Text Diff

Compare two blocks of text and see additions, deletions, and changes.

coming soon
AI

Tokenizer

Visualize how text is split into tokens for popular LLM models.

coming soon
AI

AI Cost Calculator

Estimate API costs for OpenAI, Anthropic, and other LLM providers.

coming soon
AI

Claude Code Cost

Track and estimate costs for Claude Code sessions and token usage.

coming soon