Free Online Developer Tools

A responsive collection of browser-based utilities for JSON, encoding, hashing, JWTs, CSV conversion, Markdown, colours, images, DevOps values, debugging and everyday software engineering tasks.

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CSV to JSON Converter Convert comma-separated CSV data into clean JSON for APIs, imports and data workflows. TSV to JSON Converter Convert tab-separated values into JSON objects for scripts, APIs and data processing. Base64 Encoder and Decoder Encode plain text to Base64 or decode Base64 strings back to readable text. JSON Formatter and Minifier Format, beautify, minify and validate JSON directly in your browser. PHP Unserializer Convert simple PHP serialized values into readable JSON for debugging legacy data. JSONL Validator Validate JSON Lines files and convert valid records into a JSON array. YAML to JSON Converter Convert simple YAML configuration into JSON for apps, APIs and tooling. URL Encoder and Decoder Encode URL strings safely or decode encoded URLs for inspection and debugging. Unix Timestamp Converter Convert Unix timestamps in seconds or milliseconds into readable date formats. Query Parameters to JSON Convert URL query strings into structured JSON for debugging and API work. HEX to RGB Converter Convert HEX colour values into RGB values and code snippets. .env to netlify.toml Converter Convert environment variable files into Netlify TOML build environment syntax. Image to Base64 Converter Upload an image and convert it into a Base64 data URL for embedding or testing. Base64 to Image Converter Preview Base64 image strings as images in the browser. JSON to CSV Converter Convert JSON arrays or objects into CSV for spreadsheets, exports and reports. JSON to TSV Converter Convert JSON arrays or objects into tab-separated values for data pipelines. HAR Viewer Upload a HAR file and inspect captured HTTP requests, statuses and timings. JSON to YAML Converter Convert JSON into readable YAML for configuration files and documentation. Number Base Converter Convert numbers between binary, octal, decimal and hexadecimal. CSS Inliner Inline simple CSS selectors into matching HTML elements for email and previews. Regex Tester Test JavaScript regular expressions against text and highlight matches. CSS Units Converter Convert pixels into rem values using a configurable root font size. Image Resizer Resize images in the browser and export PNG, JPEG or WebP versions. JWT Parser Decode JWT headers and payloads without verifying the signature. Hash Generator Generate SHA-1, SHA-256, SHA-384 and SHA-512 hashes in the browser. UUID Generator Generate one or more random UUIDs for testing, records and identifiers. SVG Viewer Preview SVG markup and quickly check whether it renders correctly. Lorem Ipsum Generator Generate placeholder paragraphs for layouts, designs and content testing. WebP Converter Upload an image and convert it to WebP in the browser. SQL Minifier Remove comments and extra whitespace from SQL queries. Internet Speed Test Run a lightweight browser-based download speed estimate. Random String Generator Generate secure random strings for tests, tokens and dummy values. WCAG Contrast Checker Check foreground and background colour contrast against WCAG thresholds. XML to JSON Converter Convert XML documents into JSON for easier inspection and transformation. CSV, TSV and Log Viewer Upload CSV, TSV or log files and view them in a searchable table. URL Parser Break a URL into protocol, host, path, query and hash. JWT Generator Generate unsigned JWT test tokens. Cron Expression Parser Explain cron schedules in plain English. UUID Inspector Inspect UUID version and variant. HTML Escape / Unescape Escape or unescape HTML entities. Markdown Preview Preview Markdown as HTML. JSON Diff Compare two JSON documents. Unix Permissions Calculator Convert chmod values and permissions. MIME Type Lookup Identify MIME types from filenames. Slug Generator Create SEO-friendly URL slugs. Password Generator Generate strong passwords. HTTP Status Lookup Lookup common HTTP status codes. Color Converter Convert HEX, RGB and HSL values. Bulk UUID Generator Generate hundreds of UUIDs. DNS Record Builder Generate DNS record snippets.

Browse by category

Find the right utility quickly by choosing a category. Each section groups tools that developers often use together in the same workflow.

Developer utilities for everyday engineering work

Dev Utilities is designed for small but frequent engineering tasks: formatting JSON, decoding tokens, checking URLs, generating UUIDs, converting CSV data, previewing Markdown, minifying SQL, converting colours and debugging structured data.

Instead of installing separate packages or searching through old scripts, you can open a focused utility page, enter a value, run the tool and copy the result. The tools are responsive, so they work on desktop and mobile browsers.

Why browser-based tools are useful

Many developer tasks are too small to justify writing a script but too repetitive to do manually. Browser-based tools help fill that gap. They are especially useful when preparing examples for documentation, checking API payloads, debugging integrations, working with support tickets or creating quick test values.

Privacy-conscious static design

This site is built as a static toolkit. Most tools process input locally in your browser. File inputs are only included on tools where file-based workflows are practical, such as CSV conversion, JSON formatting, HAR viewing and image conversion.

Popular workflows

Format a JSON payload, then convert it to CSV or YAML.
Decode a JWT, inspect an HTTP status code and parse a URL during API debugging.
Generate a UUID, password, random string or slug for test data.
Convert colours, preview Markdown or inline CSS for web development.
Inspect cron expressions, Unix permissions and DNS records during infrastructure work.

Latest developer guides

Read practical guides that explain the concepts behind the most common developer utilities.

What Is JSON Formatting?Learn why readable JSON matters for API development and debugging. JWT Decoder ExplainedUnderstand token headers, payloads and signatures. HTTP Status Codes ExplainedUse status codes more effectively during API debugging.