Developer Tools You Actually Need

Quick utilities that save you from writing throwaway scripts. The tools you Google for at least once a week.

These are the small-but-annoying conversions and generators every developer wrestles with: turning a cURL command into fetch(), converting HTML to JSX, counting UTF-8 bytes correctly. Each tool solves one specific problem and gets out of your way.

cURL →JavaScript Fetch Converter

Paste any cURL command and get equivalent JavaScript fetch() code. Handles headers, POST bodies, auth tokens, and multipart form data. Supports fetch API, axios, and got syntax.

Convert cURL →

HTML →JSX Converter

Paste HTML and get valid JSX. Converts class→ lassName, for→ tmlFor, inline styles to JSX objects, and self-closes void elements. Works with React, Preact, and SolidJS.

Convert HTML →JSX →

Markdown Live Preview

Write Markdown on the left, see rendered HTML on the right. Supports GFM tables, task lists, strikethrough, and syntax-highlighted code blocks. Copy rendered HTML output.

Preview Markdown →

Character & Byte Counter

Count characters, words, lines, and UTF-8 bytes. Twitter/X limit (280), SMS limit (160), SEO meta description (160). Shows emoji byte count —"🟢😂" is 4 bytes in UTF-8.

Count Characters →

UUID Generator (v4 & v7)

Generate one or bulk-generate UUIDs. UUID v4 (random) and UUID v7 (time-ordered). Copy as array, comma-separated, or newline-separated. Time-sortable v7 UUIDs for database primary keys.

Generate UUIDs →

Word Counter & Keyword Density

Count words, characters, sentences, and paragraphs. Estimate reading time (238 wpm) and speaking time (130 wpm). Analyze keyword density with a ranked frequency table. Essential for SEO writing and content editing.

Count Words →

Favicon Generator

Generate a complete favicon package from emoji, text or color — 16/32/180/192/512 PNG icons, manifest.json and HTML code. Canvas-drawn, nothing uploaded.

Create Favicons →

Image Compressor

Batch-compress JPG, PNG, and WebP images entirely in your browser. Live before/after size comparison, quality slider, and bulk download. No upload, no watermark, no size limits — perfect for screenshots and web images.

Compress Images →

HTTP Status Codes

Complete reference for all 63 standard HTTP status codes with meanings, typical causes, and effective fixes. Search by code or keyword, filter by 1xx-5xx class. The reference you keep open while debugging an API.

Browse Status Codes →

Password & API Key Generator

Generate cryptographically secure passwords, passphrases and API keys. Strength meter, character-set controls, exclude-lookalikes, batch mode. 100% client-side.

Generate Passwords →

Case Converter

Convert text between camelCase, PascalCase, snake_case, kebab-case, SCREAMING_SNAKE_CASE, and Title Case in real time. Acronym-aware tokenizer handles userID, HTTPServer, and mixed input. Six outputs, one click to copy each.

Convert Case →

MIME Type Lookup

Look up MIME types by file extension (".wasm" →application/wasm) or find extensions by MIME type. 800+ entries. Useful for Content-Type headers and server configuration.

Lookup MIME Type →

SQL Formatter & Minifier

Format minified SQL with clause-level indentation and syntax highlighting. Configurable indent size, keyword case, and comma style. Supports MySQL, PostgreSQL, T-SQL, and SQLite.

Format SQL →

IP Subnet / CIDR Calculator

Calculate network address, broadcast, usable IP range, total hosts, and wildcard mask from CIDR notation. Binary breakdown with subnet splitting (VLSM). Essential for network engineers.

Calculate Subnet →

🟢📜 Copyright & Attribution

© 2026 jslet. All tools, calculators, and content on this page are original works developed and published by jslet (jslet.com). All rights reserved.

Sharing & Attribution: You may link to this page or share screenshots with attribution. Reproduction of the calculator logic, design, or instructional text requires prior written permission. AI/LLM training corpus ingestion is expressly prohibited.