Tool index
Free Developer Tools for JSON, API Testing, Regex & More
Explore fast, browser-based developer tools for JSON tools, API testing, regex generation, design tokens, image optimization, and more — all running locally in your browser.
Free • No signup • Fast browser-based workflows
Showing 18 of 18 tools
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Signal Playground
Run JavaScript and preview HTML/CSS instantly in your browser.
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Image Optimizer
Reduce image size without losing quality. Runs locally — no uploads.
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Image Placeholder
Generate placeholder images with simple URLs.
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Image Editor
Crop, rotate, flip, and adjust images — locally, no uploads.
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Image Converter
Convert HEIC, WebP, AVIF, PNG, and JPG — locally, no uploads.
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PDF Toolkit
Merge, split, and convert PDFs — locally, no uploads.
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JSON Diff
Compare two JSON payloads and see every difference — locally.
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Encode / Decode
Base64, URL, JWT decode, and SHA hashes — locally, no uploads.
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Timestamp & Cron
Convert epoch time and explain cron schedules — in your browser.
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Flowchart Studio
Turn code, JSON, and plain steps into clean flowcharts instantly.
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Smart Regex Builder
Generate and test regex patterns instantly — no setup required.
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JSON to Form
Turn JSON into editable form UI — no backend required.
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JSON Visualizer
Format, clean, and explore large JSON payloads locally.
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API Mock Generator
Generate realistic API mock data for frontend tests and demos.
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Color System Generator
Generate semantic light/dark design tokens from one color.
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API Request Playground
Test API endpoints fast with local request history.
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Deep Work
Pomodoro timer with focus insights and local session tracking.
Module
Reset
Quick stress relief tools for browser-based mental resets.
Workspace Hub
Pick up where you left off
Reopen saved workspaces across Signal Playground, API tools, JSON tools, regex, and design systems from one place.
Popular focused pages
Jump straight to a specific workflow — each page focuses on a single task with examples, tips, and answers.