Developer Tools,
Run Locally.
No data is ever sent to a server.
All tasks are executed securely and instantly in your browser.
Popular Tools
Essential developer tools, curated for productivity.
JSON Viewer
Format and validate complex JSON data into a clean tree structure.
Mermaid Viewer
Render and preview Mermaid diagrams instantly. Supports flowcharts, sequence diagrams, and more.
OTP Generator
Generate secure 2FA codes directly in your browser without server transmission.
URL Encoder / Decoder
Encode and decode URLs, query parameters, and special characters instantly with full URL parsing.
Image Upscaler
Upscale low-resolution images using AI-powered neural network super-resolution, directly in your browser.
PDF Converter
Merge images (PNG, JPG) into a single PDF file instantly.
Diff Checker
Compare two texts or code snippets to highlight differences.
Base64 Encoder
Instantly encode or decode text and files into Base64 format.
Regex Tester
Test and debug regular expressions in real-time with visual highlighting and match details.
JWT Decoder
Decode and inspect JWT tokens instantly in your browser with signature verification.
QR Code Generator
Generate customizable QR codes with colors, logos, and download as PNG or SVG.
JSON ↔ YAML Converter
Convert between JSON and YAML formats instantly. Perfect for Kubernetes and Docker Compose configs.
HTTP Header Analyzer
Analyze HTTP response headers for security, CORS, and caching issues with a security score.
Timezone Converter
Convert Unix timestamps to dates, compare times across 10 major timezones, and format dates instantly.
SQL Query Formatter & Explainer
Format, explain, and analyze SQL queries with risk detection. Supports MySQL, PostgreSQL, T-SQL, Oracle, and SQLite.
PDF Merger & Splitter
Merge multiple PDF files or split pages into separate documents. Visual thumbnails, drag-to-reorder, 100% browser-based.
UUID Generator
Generate RFC-compliant UUIDs (v1, v3, v4, v5, v7) with bulk generation, format options, and instant copy.
Cron Generator
Generate and parse cron expressions with an interactive UI. Supports 5/6-field formats, presets, next run times, and platform-specific snippets.
cURL to Code
Convert cURL commands to Python, JavaScript, Go, Java, and 17 more languages instantly.
cURL Builder
Build cURL commands visually with a structured form. Set method, URL, headers, auth, and body.
Privacy First
No data leaves your device. Safely handle sensitive information like OTPs, JWTs, and JSON files.
Blazing Fast
Zero network latency. Powered by WASM and modern browser technologies for native-like performance.
Developer Friendly
Built by developers, for developers. Includes dark mode support, intuitive UI, and keyboard shortcuts.
About ToolRunner
ToolRunner is a free, open collection of developer utilities that run entirely in your browser. Every tool processes data locally using JavaScript and WebAssembly — nothing is uploaded, stored, or logged on a remote server. Whether you are debugging an API response, diagramming a system architecture, or converting files, ToolRunner gives you a fast, private, and distraction-free experience.
Why Browser-Based Developer Tools?
Traditional online tools require you to paste sensitive data into a form that sends it to a server. That creates privacy risks — especially when handling API tokens, configuration secrets, or proprietary schemas. Browser-based tools eliminate that risk entirely. Your data stays in the same tab where you are working, processed by code that has already been downloaded to your machine. The result is zero network latency and complete data privacy by default.
Available Tools
- JSON Viewer — Parse, format, minify, and explore JSON with tree, text, and table views
- Mermaid Viewer — Render flowcharts, sequence diagrams, class diagrams, and more from Mermaid syntax
- OTP Generator — Generate time-based one-time passwords (TOTP) for two-factor authentication
- URL Encoder / Decoder — Encode and decode URLs and query parameters with full URL structure parsing
- Image Upscaler — Enhance low-resolution images using AI-powered upscaling
- PDF Converter — Merge multiple images into a single PDF document
- Diff Checker — Compare two text or code snippets and highlight every difference
- Base64 Encoder — Encode or decode text and files to and from Base64 format
- Regex Tester — Test and debug regular expressions with real-time highlighting and match details
- JWT Decoder — Decode and inspect JSON Web Tokens with signature verification
- QR Code Generator — Create customizable QR codes with colors, logos, and download as PNG or SVG
- JSON ↔ YAML Converter — Convert between JSON and YAML formats for Kubernetes, Docker Compose, and other DevOps configs
- HTTP Header Analyzer — Analyze HTTP response headers for security vulnerabilities, CORS issues, and caching policies
- Timezone Converter — Convert Unix timestamps to dates, compare times across major timezones, and format dates in multiple formats
- SQL Query Formatter & Explainer — Format, explain, and analyze SQL queries with multi-dialect support and risk detection
Built for Developers
Every tool is designed with a developer-first mindset: dark mode support, keyboard shortcuts, drag-to-resize panes, fullscreen modes, and instant feedback. The interface stays out of your way so you can focus on the task at hand. ToolRunner loads fast, works offline after the first visit, and never interrupts you with ads or sign-up prompts.
Frequently Asked Questions
- Is ToolRunner really free?
- Yes. All tools are free to use with no sign-up, no usage limits, and no premium tiers.
- Does ToolRunner collect my data?
- No. Every tool runs entirely in your browser. We do not collect, transmit, or store any data you process.
- Can I use ToolRunner offline?
- Yes. Once the page has loaded, most tools work without an internet connection because all processing happens client-side.
- Which browsers are supported?
- ToolRunner works in all modern browsers including Chrome, Firefox, Safari, and Edge. We recommend using the latest version for the best experience.