// tools

Free Developer Tools

28 client-side utilities across 8 categories — AI prompts, encoding, DevOps, security, and more. No account, no uploads, no tracking. Everything runs in your browser.

6 AI Tools 3 Encoding & Crypto 2 Data & Formats 5 DevOps 1 Security & Auth 3 Code & Text 6 Media & Files 2 Reference & Planning

AI Tools new

Prompt engineering, workflow optimization, and AI-powered utilities for the era of intelligent automation.

6 tools
// ai

Prompt Optimizer

Multi-step wizard that assembles production-ready prompts for Claude, GPT-4, Gemini and open-source models — deterministic, no API calls.

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Token Counter

Count tokens and estimate API costs for GPT-4o, Claude 3.5, Gemini, and more — real-time, no API calls, no data leaves your browser.

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Commit Message Generator

6-step wizard for conventional commits — type, scope, description, breaking changes, body, issue refs, and branch name suggestion.

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AI Model Picker

Answer 5 questions about use case, budget, context, speed, and deployment — get the top 3 AI models with pros, cons, and pricing.

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LLM Cost Estimator

Live API cost comparison across 300+ models from OpenRouter — enter token counts, sort by price, filter by provider.

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AI Persona Picker

20 ready-made system prompt personas for engineers, writers, and analysts. Copy with one click or save your own to localStorage.

Encoding & Crypto

Encode, decode, hash, and generate unique identifiers for data pipelines and API integrations.

3 tools
// encoding

Base64 Converter

Convert, validate, and repair Base64/Base64URL payloads fully client-side.

 // encoding

Hash Generator

Generate and verify MD5, SHA-1, SHA-256, SHA-384, and SHA-512 hashes instantly.

 // encoding

UUID Generator

Generate up to 100 UUID v4 values instantly. Toggle hyphens, copy all, or download as text.

Data & Formats

Parse, convert, compare, and validate JSON, YAML, and other structured data formats used in APIs and config files.

2 tools
// data

YAML ↔ JSON

Bidirectional YAML and JSON converter with real-time validation and inline error reporting. No server, no logs.

 // data

Diff Viewer

Compare two texts side-by-side or unified — added, removed, and unchanged lines highlighted instantly.

DevOps

Essential tools for infrastructure engineers — cron scheduling, file permissions, uptime calculations, and log analysis.

5 tools
// devops

Cron Parser

Translate cron expressions into plain English and preview the next scheduled run times.

 // devops

Timestamp Converter

Convert Unix timestamps (seconds or ms) to UTC, local time, and relative time — and back.

 // devops

chmod Calculator

Click checkboxes or type an octal to get symbolic notation and a ready-to-copy chmod command.

 // devops

SLA Calculator

Enter an uptime percentage and see exact downtime per day, week, month, and year.

 // devops

Log Viewer

Parse, filter, and inspect structured log files directly in the browser.

Security & Auth

Inspect and audit authentication tokens, claims, and access control permissions without sending data to any server.

1 tool
// security

JWT Inspector

Decode, inspect, and audit JWT tokens — expiry countdown, claim explanations, and security warnings.

Code & Text

Lint code in real time, test regex patterns, and write formatted documentation with live preview.

3 tools
// code

Regex Tester

Live regex matching with coloured capture groups, match positions, and one-click common patterns.

 // code

Online Linters

Real-time code linter for JSON, YAML, JavaScript, and Markdown powered by Monaco Editor.

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Markdown Editor

Live Markdown editor with preview, export, and formatting shortcuts.

Media & Files

Optimize, convert, crop, resize, and dissect images in the browser — nothing is uploaded to any server.

6 tools
popular // media

Image Optimizer

Convert images to WebP in-browser. Adjust quality, resize, batch download — zero server uploads.

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Image Crop

Drag handles to crop any image. Lock aspect ratios, enter exact pixel coordinates, download as PNG — no uploads.

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Image Resize

Resize images by exact pixels, percentage, or fit-box. Batch process up to 20 files, export PNG/JPEG/WebP.

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Sprite Sheet Splitter

Extract individual sprites from a sheet using alpha transparency or a color-key background. Download as separate PNGs.

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Sprite Asset Detector

Visualize bounding boxes for every sprite on a sheet. Export an annotated PNG or a JSON atlas for Phaser, PixiJS, or Unity.

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Background Remover

Remove or replace a solid background color. Click to sample, set tolerance, export transparent PNG — ideal for sprites and logos.

Reference & Planning

Quick-access reference guides and estimation calculators for software development teams.

2 tools
// reference

HTTP Status Codes

Search and filter all HTTP status codes with plain-English descriptions and REST API guidance.

 // reference

Estimators

Project and effort estimation tools including Planning Poker and T-shirt sizing for engineering teams.

Why use browser-based developer tools?

Browser-based tools run entirely in your machine using Web APIs like SubtleCrypto, Canvas, FileReader, and TextEncoder. Unlike server-side tools, your code, tokens, and files never leave your device — which is critical when working with JWTs, API keys, sensitive logs, or proprietary source code.

  • Privacy by design: Zero data transmission. Zero storage.
  • Works offline: Once loaded, tools keep working without internet.
  • No rate limits: Process as much data as your browser allows.
  • Instant: No round-trip latency. Results appear as you type.

What is a Prompt Optimizer?

A Prompt Optimizer is a structured tool that helps you apply prompt engineering best practices without having to memorize them. Instead of writing prompts from scratch, you answer 5 targeted questions about your use case and the tool assembles a production-ready prompt.

Our Prompt Optimizer supports Claude, GPT-4, Gemini, and open-source models. It applies model-specific techniques: XML tags for Claude, system/user message separation for GPT, and instruction-following format for open-source models. The result is always deterministic — no AI API calls needed.

Frequently Asked Questions

What is Base64 encoding and when should I use it?
Base64 is a binary-to-text encoding scheme that converts binary data into ASCII characters. It's widely used to safely transmit binary data (like images or files) over text-based protocols such as HTTP headers, JSON APIs, and email attachments. Use our Base64 Converter to encode or decode instantly in your browser.
How do I decode and inspect a JWT token?
A JWT (JSON Web Token) consists of three Base64URL-encoded parts: header, payload, and signature. You can decode the header and payload without the secret key using our JWT Inspector — it also shows claim meanings, expiry countdown, and security warnings like weak algorithms or missing claims.
What does a cron expression like '0 9 * * 1-5' mean?
That cron expression means 'run at 09:00 every weekday (Monday through Friday)'. Cron expressions have five fields: minute, hour, day-of-month, month, and day-of-week. Our Cron Parser translates any cron expression into plain English and shows the next 10 upcoming run times.
How do I calculate chmod permissions?
Unix chmod permissions use an octal notation (e.g. 755) representing read/write/execute rights for owner, group, and others. Our chmod Calculator lets you click checkboxes to build permissions visually or type an octal to get the symbolic notation (e.g. rwxr-xr-x) and a ready-to-copy chmod command.
What is a Prompt Optimizer and how does it work?
A Prompt Optimizer helps you write better prompts for AI models like Claude, GPT-4, and Gemini. Our tool walks you through 5 questions — target platform, task type, output format, response length, and your task description — then assembles a production-ready prompt using proven prompt engineering techniques like role assignment, output format specification, and model-specific formatting. It's entirely deterministic: no AI API calls, runs fully in your browser.
How do I convert YAML to JSON (and back)?
YAML and JSON are both widely used data serialization formats. YAML is human-readable and common in DevOps configuration files (Docker, Kubernetes, GitHub Actions), while JSON is the standard for APIs and web data. Our YAML ↔ JSON converter transforms between both formats instantly with real-time validation.
Are these developer tools safe? Is my data private?
Yes — every tool on this page runs entirely in your browser using Web APIs. No data is sent to any server. Your code, tokens, files, and text never leave your machine. This includes sensitive tools like the JWT Inspector and Hash Generator.
What is SLA uptime and how is downtime calculated?
SLA (Service Level Agreement) uptime refers to the guaranteed percentage of time a service will be available. '99.9% uptime' (three nines) means a maximum of 8.76 hours of downtime per year. Our SLA Calculator shows exact allowed downtime per day, week, month, and year for any uptime percentage.