katlab tools

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katlab tools

Small, free web utilities that run entirely in your browser.

No uploads · no accounts · no tracking

I'm always looking for fun, interesting and challenging tools to build — got one that fits, or something that would solve a real-world problem for you? Suggest a tool → Your email is only ever used to reply to your request — never for marketing, newsletters, or shared with anyone.

Bundle files into a .zip or extract an archive — locally, no upload.

PNG · JPG · WebP conversion and resize — locally, no upload.

Convert iPhone HEIC & HEIF photos to JPG, PNG or WebP — locally, no upload.

Merge PDFs into one or split out pages — locally, no upload.

Preview, rotate, delete & reorder PDF pages — locally, no upload.

Draw, highlight, sign & truly redact PDFs — locally, no upload.

Draw, type or upload a signature & place it on any page — locally, no upload.

Shrink scanned & image-heavy PDFs 4–10× — locally, no upload.

Remove PDF restrictions & known open passwords — locally, no upload.

Shrink JPG, PNG & WebP — lossless, near-lossless or lossy — locally, no upload.

Video Compressor

Shrink MP4 video by quality or to a target size — locally, no upload.

Turn any video clip into an animated GIF — locally, no upload.

Cut a clip instantly (no re-encode) or frame-exact — locally, no upload.

Audio Converter

MP3, WAV, OGG, FLAC, M4A — convert, trim or extract from video — locally, no upload.

Pull the MP3 soundtrack out of MP4, MOV & WebM — locally, no upload.

SRT ↔ VTT Converter

Convert subtitles both ways + time-shift resync — locally, no upload.

Combine JPG, PNG & WebP into a single PDF — locally, no upload.

PDF to PowerPoint

Every PDF page becomes a PPTX slide, pixel-perfect — locally, no upload.

Convert PDF pages to JPG or PNG images — locally, no upload.

Markdown to PDF

Polished PDFs from Markdown with themes, code & math — no watermark, no upload.

PDF to Markdown

Turn a PDF into clean Markdown with headings & lists — locally, no upload.

Images to PowerPoint

Turn JPG & PNG photos into PPTX slides — locally, no upload.

QR Code Generator

Turn a link or text into a QR code — download PNG or SVG, no upload.

Barcode Generator

Code 128, EAN-13, UPC-A & more — SVG or PNG, no upload.

Archive Extractor

Open RAR, 7z, TAR & TAR.GZ — password-protected too. Locally, no upload.

Favicon Generator

Make favicon.ico & PNG sizes from any image — locally, no upload.

Rasterize SVG to crisp PNG at any scale — locally, no upload.

Minify SVG with SVGO, safe defaults + live preview — locally, no upload.

EXIF Metadata Remover

Strip GPS & camera data from JPG, PNG & WebP — locally, no upload.

Developer & text tools

Color & Contrast

WCAG contrast checker + HEX/RGB/HSL/OKLCH converter — no upload.

Beautify, validate & minify JSON — locally, no upload.

Generate TypeScript, Go, Rust & Python types from JSON — locally, no upload.

Beautify & minify SQL — MySQL, Postgres, SQLite & more — locally, no upload.

SQLite Playground

Run real SQL on your CSV & JSON with SQLite — locally, no upload.

Base64 Encode / Decode

Convert text or files to and from Base64 — locally, no upload.

MD5, SHA-1, SHA-256 & SHA-512 of text or files — locally, no upload.

Random v4 UUIDs, single or in bulk — locally, no upload.

Decode a JSON Web Token's header & payload — locally, no upload.

Convert a curl command to Python, fetch, Go & more — locally, no upload.

camelCase, snake_case, kebab-case & more — locally, no upload.

CSV / JSON Converter

Convert CSV to JSON and back, RFC 4180 — locally, no upload.

JSON Escape / Unescape

Text to JSON string literal and back, \uXXXX option — locally, no upload.

Run real jq filters over JSON, live — locally, no upload.

YAML ↔ JSON Converter

Convert YAML to JSON and back, multi-doc aware — locally, no upload.

Format, validate & convert XML ↔ JSON — locally, no upload.

HTML ↔ Markdown

Convert HTML to clean Markdown and back, GFM tables — locally, no upload.

Test regular expressions with live match highlighting — no upload.

Crontab schedules in plain English + next run times — locally, no upload.

Timestamp Converter

Unix epoch to date and back, any time zone — locally, no upload.

Compare two texts by line, word or character — locally, no upload.

Text Compression

Gzip, deflate or LZ-string text to Base64 & back — no upload.

.NET Ticks Converter

C# DateTime.Ticks to date and back, exact BigInt math — no upload.

URL / HTML Entity Encode

Percent-encode URLs & escape HTML entities — locally, no upload.

Password Generator

Strong random passwords, crypto-secure — locally, no upload.

Encrypt any file with a passphrase, AES-256-GCM — locally, no upload.

Calculators

Seller Fee Calculator

Net profit after eBay, Etsy, Depop & Mercari fees — runs in your browser.